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  21 <title>Chapter 6. BIND 9 Configuration Reference</title>
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  31 <tr><th colspan="3" align="center">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</th></tr>
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  42 <div class="chapter" lang="en">
  43 <div class="titlepage"><div><div><h2 class="title">
  44 <a name="Bv9ARM.ch06"></a>Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</h2></div></div></div>
  45 <div class="toc">
  46 <p><b>Table of Contents</b></p>
  47 <dl>
  48 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#configuration_file_elements">Configuration File Elements</a></span></dt>
  49 <dd><dl>
  50 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#address_match_lists">Address Match Lists</a></span></dt>
  51 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2573281">Comment Syntax</a></span></dt>
  52 </dl></dd>
  53 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#Configuration_File_Grammar">Configuration File Grammar</a></span></dt>
  54 <dd><dl>
  55 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574009"><span><strong class="command">acl</strong></span> Statement Grammar</a></span></dt>
  56 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#acl"><span><strong class="command">acl</strong></span> Statement Definition and
  57           Usage</a></span></dt>
  58 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574321"><span><strong class="command">controls</strong></span> Statement Grammar</a></span></dt>
  59 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage"><span><strong class="command">controls</strong></span> Statement Definition and
  60           Usage</a></span></dt>
  61 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574748"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574765"><span><strong class="command">include</strong></span> Statement Definition and
  63           Usage</a></span></dt>
  64 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574789"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574812"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574903"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575029"><span><strong class="command">logging</strong></span> Statement Definition and
  68           Usage</a></span></dt>
  69 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577252"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577336"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577400"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577517"><span><strong class="command">masters</strong></span> Statement Definition and
  73           Usage</a></span></dt>
  74 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577539"><span><strong class="command">options</strong></span> Statement Grammar</a></span></dt>
  75 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#options"><span><strong class="command">options</strong></span> Statement Definition and
  76           Usage</a></span></dt>
  77 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_grammar"><span><strong class="command">server</strong></span> Statement Grammar</a></span></dt>
  78 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_definition_and_usage"><span><strong class="command">server</strong></span> Statement Definition and
  79             Usage</a></span></dt>
  80 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#statschannels"><span><strong class="command">statistics-channels</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2591758"><span><strong class="command">statistics-channels</strong></span> Statement Definition and
  82             Usage</a></span></dt>
  83 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#trusted-keys"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2592176"><span><strong class="command">trusted-keys</strong></span> Statement Definition
  85             and Usage</a></span></dt>
  86 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2592222"><span><strong class="command">managed-keys</strong></span> Statement Grammar</a></span></dt>
  87 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#managed-keys"><span><strong class="command">managed-keys</strong></span> Statement Definition
  88             and Usage</a></span></dt>
  89 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span><strong class="command">view</strong></span> Statement Grammar</a></span></dt>
  90 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2592589"><span><strong class="command">view</strong></span> Statement Definition and Usage</a></span></dt>
  91 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span><strong class="command">zone</strong></span>
  92             Statement Grammar</a></span></dt>
  93 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2594602"><span><strong class="command">zone</strong></span> Statement Definition and Usage</a></span></dt>
  94 </dl></dd>
  95 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#id2598289">Zone File</a></span></dt>
  96 <dd><dl>
  97 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#types_of_resource_records_and_when_to_use_them">Types of Resource Records and When to Use Them</a></span></dt>
  98 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2600587">Discussion of MX Records</a></span></dt>
  99 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
 100 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2601134">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2601261">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2601534"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</a></span></dt>
 103 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
 104 </dl></dd>
 105 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#statistics">BIND9 Statistics</a></span></dt>
 106 <dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch06.html#statistics_counters">Statistics Counters</a></span></dt></dl></dd>
 107 </dl>
 108 </div>
 109 <p>
 110       <acronym class="acronym">BIND</acronym> 9 configuration is broadly similar
 111       to <acronym class="acronym">BIND</acronym> 8; however, there are a few new
 112       areas
 113       of configuration, such as views. <acronym class="acronym">BIND</acronym>
 114       8 configuration files should work with few alterations in <acronym class="acronym">BIND</acronym>
 115       9, although more complex configurations should be reviewed to check
 116       if they can be more efficiently implemented using the new features
 117       found in <acronym class="acronym">BIND</acronym> 9.
 118     </p>
 119 <p>
 120       <acronym class="acronym">BIND</acronym> 4 configuration files can be
 121       converted to the new format
 122       using the shell script
 123       <code class="filename">contrib/named-bootconf/named-bootconf.sh</code>.
 124     </p>
 125 <div class="sect1" lang="en">
 126 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 127 <a name="configuration_file_elements"></a>Configuration File Elements</h2></div></div></div>
 128 <p>
 129         Following is a list of elements used throughout the <acronym class="acronym">BIND</acronym> configuration
 130         file documentation:
 131       </p>
 132 <div class="informaltable"><table border="1">
 133 <colgroup>
 134 <col>
 135 <col>
 136 </colgroup>
 137 <tbody>
 138 <tr>
 139 <td>
 140                 <p>
 141                   <code class="varname">acl_name</code>
 142                 </p>
 143               </td>
 144 <td>
 145                 <p>
 146                   The name of an <code class="varname">address_match_list</code> as
 147                   defined by the <span><strong class="command">acl</strong></span> statement.
 148                 </p>
 149               </td>
 150 </tr>
 151 <tr>
 152 <td>
 153                 <p>
 154                   <code class="varname">address_match_list</code>
 155                 </p>
 156               </td>
 157 <td>
 158                 <p>
 159                   A list of one or more
 160                   <code class="varname">ip_addr</code>,
 161                   <code class="varname">ip_prefix</code>, <code class="varname">key_id</code>,
 162                   or <code class="varname">acl_name</code> elements, see
 163                   <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a>.
 164                 </p>
 165               </td>
 166 </tr>
 167 <tr>
 168 <td>
 169                 <p>
 170                   <code class="varname">masters_list</code>
 171                 </p>
 172               </td>
 173 <td>
 174                 <p>
 175                   A named list of one or more <code class="varname">ip_addr</code>
 176                   with optional <code class="varname">key_id</code> and/or
 177                   <code class="varname">ip_port</code>.
 178                   A <code class="varname">masters_list</code> may include other
 179                   <code class="varname">masters_lists</code>.
 180                 </p>
 181               </td>
 182 </tr>
 183 <tr>
 184 <td>
 185                 <p>
 186                   <code class="varname">domain_name</code>
 187                 </p>
 188               </td>
 189 <td>
 190                 <p>
 191                   A quoted string which will be used as
 192                   a DNS name, for example "<code class="literal">my.test.domain</code>".
 193                 </p>
 194               </td>
 195 </tr>
 196 <tr>
 197 <td>
 198                 <p>
 199                   <code class="varname">namelist</code>
 200                 </p>
 201               </td>
 202 <td>
 203                 <p>
 204                   A list of one or more <code class="varname">domain_name</code>
 205                   elements.
 206                 </p>
 207               </td>
 208 </tr>
 209 <tr>
 210 <td>
 211                 <p>
 212                   <code class="varname">dotted_decimal</code>
 213                 </p>
 214               </td>
 215 <td>
 216                 <p>
 217                   One to four integers valued 0 through
 218                   255 separated by dots (`.'), such as <span><strong class="command">123</strong></span>,
 219                   <span><strong class="command">45.67</strong></span> or <span><strong class="command">89.123.45.67</strong></span>.
 220                 </p>
 221               </td>
 222 </tr>
 223 <tr>
 224 <td>
 225                 <p>
 226                   <code class="varname">ip4_addr</code>
 227                 </p>
 228               </td>
 229 <td>
 230                 <p>
 231                   An IPv4 address with exactly four elements
 232                   in <code class="varname">dotted_decimal</code> notation.
 233                 </p>
 234               </td>
 235 </tr>
 236 <tr>
 237 <td>
 238                 <p>
 239                   <code class="varname">ip6_addr</code>
 240                 </p>
 241               </td>
 242 <td>
 243                 <p>
 244                   An IPv6 address, such as <span><strong class="command">2001:db8::1234</strong></span>.
 245                   IPv6 scoped addresses that have ambiguity on their
 246                   scope zones must be disambiguated by an appropriate
 247                   zone ID with the percent character (`%') as
 248                   delimiter.  It is strongly recommended to use
 249                   string zone names rather than numeric identifiers,
 250                   in order to be robust against system configuration
 251                   changes.  However, since there is no standard
 252                   mapping for such names and identifier values,
 253                   currently only interface names as link identifiers
 254                   are supported, assuming one-to-one mapping between
 255                   interfaces and links.  For example, a link-local
 256                   address <span><strong class="command">fe80::1</strong></span> on the link
 257                   attached to the interface <span><strong class="command">ne0</strong></span>
 258                   can be specified as <span><strong class="command">fe80::1%ne0</strong></span>.
 259                   Note that on most systems link-local addresses
 260                   always have the ambiguity, and need to be
 261                   disambiguated.
 262                 </p>
 263               </td>
 264 </tr>
 265 <tr>
 266 <td>
 267                 <p>
 268                   <code class="varname">ip_addr</code>
 269                 </p>
 270               </td>
 271 <td>
 272                 <p>
 273                   An <code class="varname">ip4_addr</code> or <code class="varname">ip6_addr</code>.
 274                 </p>
 275               </td>
 276 </tr>
 277 <tr>
 278 <td>
 279                 <p>
 280                   <code class="varname">ip_dscp</code>
 281                 </p>
 282               </td>
 283 <td>
 284                 <p>
 285                   A <code class="varname">number</code> between 0 and 63, used
 286                   to select a differentiated services code point (DSCP)
 287                   value for use with outgoing traffic on operating systems
 288                   that support DSCP.
 289                 </p>
 290               </td>
 291 </tr>
 292 <tr>
 293 <td>
 294                 <p>
 295                   <code class="varname">ip_port</code>
 296                 </p>
 297               </td>
 298 <td>
 299                 <p>
 300                   An IP port <code class="varname">number</code>.
 301                   The <code class="varname">number</code> is limited to 0
 302                   through 65535, with values
 303                   below 1024 typically restricted to use by processes running
 304                   as root.
 305                   In some cases, an asterisk (`*') character can be used as a
 306                   placeholder to
 307                   select a random high-numbered port.
 308                 </p>
 309               </td>
 310 </tr>
 311 <tr>
 312 <td>
 313                 <p>
 314                   <code class="varname">ip_prefix</code>
 315                 </p>
 316               </td>
 317 <td>
 318                 <p>
 319                   An IP network specified as an <code class="varname">ip_addr</code>,
 320                   followed by a slash (`/') and then the number of bits in the
 321                   netmask.
 322                   Trailing zeros in a <code class="varname">ip_addr</code>
 323                   may omitted.
 324                   For example, <span><strong class="command">127/8</strong></span> is the
 325                   network <span><strong class="command">127.0.0.0</strong></span> with
 326                   netmask <span><strong class="command">255.0.0.0</strong></span> and <span><strong class="command">1.2.3.0/28</strong></span> is
 327                   network <span><strong class="command">1.2.3.0</strong></span> with netmask <span><strong class="command">255.255.255.240</strong></span>.
 328                 </p>
 329                 <p>
 330                   When specifying a prefix involving a IPv6 scoped address
 331                   the scope may be omitted.  In that case the prefix will
 332                   match packets from any scope.
 333                 </p>
 334               </td>
 335 </tr>
 336 <tr>
 337 <td>
 338                 <p>
 339                   <code class="varname">key_id</code>
 340                 </p>
 341               </td>
 342 <td>
 343                 <p>
 344                   A <code class="varname">domain_name</code> representing
 345                   the name of a shared key, to be used for transaction
 346                   security.
 347                 </p>
 348               </td>
 349 </tr>
 350 <tr>
 351 <td>
 352                 <p>
 353                   <code class="varname">key_list</code>
 354                 </p>
 355               </td>
 356 <td>
 357                 <p>
 358                   A list of one or more
 359                   <code class="varname">key_id</code>s,
 360                   separated by semicolons and ending with a semicolon.
 361                 </p>
 362               </td>
 363 </tr>
 364 <tr>
 365 <td>
 366                 <p>
 367                   <code class="varname">number</code>
 368                 </p>
 369               </td>
 370 <td>
 371                 <p>
 372                   A non-negative 32-bit integer
 373                   (i.e., a number between 0 and 4294967295, inclusive).
 374                   Its acceptable value might further
 375                   be limited by the context in which it is used.
 376                 </p>
 377               </td>
 378 </tr>
 379 <tr>
 380 <td>
 381                 <p>
 382                   <code class="varname">path_name</code>
 383                 </p>
 384               </td>
 385 <td>
 386                 <p>
 387                   A quoted string which will be used as
 388                   a pathname, such as <code class="filename">zones/master/my.test.domain</code>.
 389                 </p>
 390               </td>
 391 </tr>
 392 <tr>
 393 <td>
 394                 <p>
 395                   <code class="varname">port_list</code>
 396                 </p>
 397               </td>
 398 <td>
 399                 <p>
 400                   A list of an <code class="varname">ip_port</code> or a port
 401                   range.
 402                   A port range is specified in the form of
 403                   <strong class="userinput"><code>range</code></strong> followed by
 404                   two <code class="varname">ip_port</code>s,
 405                   <code class="varname">port_low</code> and
 406                   <code class="varname">port_high</code>, which represents
 407                   port numbers from <code class="varname">port_low</code> through
 408                   <code class="varname">port_high</code>, inclusive.
 409                   <code class="varname">port_low</code> must not be larger than
 410                   <code class="varname">port_high</code>.
 411                   For example,
 412                   <strong class="userinput"><code>range 1024 65535</code></strong> represents
 413                   ports from 1024 through 65535.
 414                   In either case an asterisk (`*') character is not
 415                   allowed as a valid <code class="varname">ip_port</code>.
 416                 </p>
 417               </td>
 418 </tr>
 419 <tr>
 420 <td>
 421                 <p>
 422                   <code class="varname">size_spec</code>
 423                 </p>
 424               </td>
 425 <td>
 426                 <p>
 427                   A 64-bit unsigned integer, or the keywords
 428                   <strong class="userinput"><code>unlimited</code></strong> or
 429                   <strong class="userinput"><code>default</code></strong>.
 430                 </p>
 431                 <p>
 432                   Integers may take values
 433                   0 &lt;= value &lt;= 18446744073709551615, though
 434                   certain parameters
 435                   (such as <span><strong class="command">max-journal-size</strong></span>) may
 436                   use a more limited range within these extremes.
 437                   In most cases, setting a value to 0 does not
 438                   literally mean zero; it means "undefined" or
 439                   "as big as possible", depending on the context.
 440                   See the explanations of particular parameters
 441                   that use <code class="varname">size_spec</code>
 442                   for details on how they interpret its use.
 443                 </p>
 444                 <p>
 445                   Numeric values can optionally be followed by a
 446                   scaling factor:
 447                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 448                   for kilobytes,
 449                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 450                   for megabytes, and
 451                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong>
 452                   for gigabytes, which scale by 1024, 1024*1024, and
 453                   1024*1024*1024 respectively.
 454                 </p>
 455                 <p>
 456                   <code class="varname">unlimited</code> generally means
 457                   "as big as possible", and is usually the best
 458                   way to safely set a very large number.
 459                 </p>
 460                 <p>
 461                   <code class="varname">default</code>
 462                   uses the limit that was in force when the server was started.
 463                 </p>
 464               </td>
 465 </tr>
 466 <tr>
 467 <td>
 468                 <p>
 469                   <code class="varname">yes_or_no</code>
 470                 </p>
 471               </td>
 472 <td>
 473                 <p>
 474                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 475                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 476                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 477                   and <strong class="userinput"><code>0</code></strong>.
 478                 </p>
 479               </td>
 480 </tr>
 481 <tr>
 482 <td>
 483                 <p>
 484                   <code class="varname">dialup_option</code>
 485                 </p>
 486               </td>
 487 <td>
 488                 <p>
 489                   One of <strong class="userinput"><code>yes</code></strong>,
 490                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 491                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 492                   <strong class="userinput"><code>passive</code></strong>.
 493                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 494                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 495                   are restricted to slave and stub zones.
 496                 </p>
 497               </td>
 498 </tr>
 499 </tbody>
 500 </table></div>
 501 <div class="sect2" lang="en">
 502 <div class="titlepage"><div><div><h3 class="title">
 503 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 504 <div class="sect3" lang="en">
 505 <div class="titlepage"><div><div><h4 class="title">
 506 <a name="id2573115"></a>Syntax</h4></div></div></div>
 507 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 508   [<span class="optional"> address_match_list_element; ... </span>]
 509 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 510    key key_id | acl_name | { address_match_list } )
 511 </pre>
 512 </div>
 513 <div class="sect3" lang="en">
 514 <div class="titlepage"><div><div><h4 class="title">
 515 <a name="id2573143"></a>Definition and Usage</h4></div></div></div>
 516 <p>
 517             Address match lists are primarily used to determine access
 518             control for various server operations. They are also used in
 519             the <span><strong class="command">listen-on</strong></span> and <span><strong class="command">sortlist</strong></span>
 520             statements. The elements which constitute an address match
 521             list can be any of the following:
 522           </p>
 523 <div class="itemizedlist"><ul type="disc">
 524 <li>an IP address (IPv4 or IPv6)</li>
 525 <li>an IP prefix (in `/' notation)</li>
 526 <li>
 527                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 528                 statement
 529               </li>
 530 <li>the name of an address match list defined with
 531                 the <span><strong class="command">acl</strong></span> statement
 532               </li>
 533 <li>a nested address match list enclosed in braces</li>
 534 </ul></div>
 535 <p>
 536             Elements can be negated with a leading exclamation mark (`!'),
 537             and the match list names "any", "none", "localhost", and
 538             "localnets" are predefined. More information on those names
 539             can be found in the description of the acl statement.
 540           </p>
 541 <p>
 542             The addition of the key clause made the name of this syntactic
 543             element something of a misnomer, since security keys can be used
 544             to validate access without regard to a host or network address.
 545             Nonetheless, the term "address match list" is still used
 546             throughout the documentation.
 547           </p>
 548 <p>
 549             When a given IP address or prefix is compared to an address
 550             match list, the comparison takes place in approximately O(1)
 551             time.  However, key comparisons require that the list of keys
 552             be traversed until a matching key is found, and therefore may
 553             be somewhat slower.
 554           </p>
 555 <p>
 556             The interpretation of a match depends on whether the list is being
 557             used for access control, defining <span><strong class="command">listen-on</strong></span> ports, or in a
 558             <span><strong class="command">sortlist</strong></span>, and whether the element was negated.
 559           </p>
 560 <p>
 561             When used as an access control list, a non-negated match
 562             allows access and a negated match denies access. If
 563             there is no match, access is denied. The clauses
 564             <span><strong class="command">allow-notify</strong></span>,
 565             <span><strong class="command">allow-recursion</strong></span>,
 566             <span><strong class="command">allow-recursion-on</strong></span>,
 567             <span><strong class="command">allow-query</strong></span>,
 568             <span><strong class="command">allow-query-on</strong></span>,
 569             <span><strong class="command">allow-query-cache</strong></span>,
 570             <span><strong class="command">allow-query-cache-on</strong></span>,
 571             <span><strong class="command">allow-transfer</strong></span>,
 572             <span><strong class="command">allow-update</strong></span>,
 573             <span><strong class="command">allow-update-forwarding</strong></span>, and
 574             <span><strong class="command">blackhole</strong></span> all use address match
 575             lists.  Similarly, the <span><strong class="command">listen-on</strong></span> option will cause the
 576             server to refuse queries on any of the machine's
 577             addresses which do not match the list.
 578           </p>
 579 <p>
 580             Order of insertion is significant.  If more than one element
 581             in an ACL is found to match a given IP address or prefix,
 582             preference will be given to the one that came
 583             <span class="emphasis"><em>first</em></span> in the ACL definition.
 584             Because of this first-match behavior, an element that
 585             defines a subset of another element in the list should
 586             come before the broader element, regardless of whether
 587             either is negated. For example, in
 588             <span><strong class="command">1.2.3/24; ! 1.2.3.13;</strong></span>
 589             the 1.2.3.13 element is completely useless because the
 590             algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
 591             element.  Using <span><strong class="command">! 1.2.3.13; 1.2.3/24</strong></span> fixes
 592             that problem by having 1.2.3.13 blocked by the negation, but
 593             all other 1.2.3.* hosts fall through.
 594           </p>
 595 </div>
 596 </div>
 597 <div class="sect2" lang="en">
 598 <div class="titlepage"><div><div><h3 class="title">
 599 <a name="id2573281"></a>Comment Syntax</h3></div></div></div>
 600 <p>
 601           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 602           comments to appear
 603           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 604           file. To appeal to programmers of all kinds, they can be written
 605           in the C, C++, or shell/perl style.
 606         </p>
 607 <div class="sect3" lang="en">
 608 <div class="titlepage"><div><div><h4 class="title">
 609 <a name="id2573296"></a>Syntax</h4></div></div></div>
 610 <p>
 611             </p>
 612 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 613 <p>
 614             </p>
 615 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 616 <p>
 617             </p>
 618 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells
 619 # and perl</pre>
 620 <p>
 621           </p>
 622 </div>
 623 <div class="sect3" lang="en">
 624 <div class="titlepage"><div><div><h4 class="title">
 625 <a name="id2573394"></a>Definition and Usage</h4></div></div></div>
 626 <p>
 627             Comments may appear anywhere that whitespace may appear in
 628             a <acronym class="acronym">BIND</acronym> configuration file.
 629           </p>
 630 <p>
 631             C-style comments start with the two characters /* (slash,
 632             star) and end with */ (star, slash). Because they are completely
 633             delimited with these characters, they can be used to comment only
 634             a portion of a line or to span multiple lines.
 635           </p>
 636 <p>
 637             C-style comments cannot be nested. For example, the following
 638             is not valid because the entire comment ends with the first */:
 639           </p>
 640 <p>
 641
 642 </p>
 643 <pre class="programlisting">/* This is the start of a comment.
 644    This is still part of the comment.
 645 /* This is an incorrect attempt at nesting a comment. */
 646    This is no longer in any comment. */
 647 </pre>
 648 <p>
 649
 650           </p>
 651 <p>
 652             C++-style comments start with the two characters // (slash,
 653             slash) and continue to the end of the physical line. They cannot
 654             be continued across multiple physical lines; to have one logical
 655             comment span multiple lines, each line must use the // pair.
 656             For example:
 657           </p>
 658 <p>
 659
 660 </p>
 661 <pre class="programlisting">// This is the start of a comment.  The next line
 662 // is a new comment, even though it is logically
 663 // part of the previous comment.
 664 </pre>
 665 <p>
 666
 667           </p>
 668 <p>
 669             Shell-style (or perl-style, if you prefer) comments start
 670             with the character <code class="literal">#</code> (number sign)
 671             and continue to the end of the
 672             physical line, as in C++ comments.
 673             For example:
 674           </p>
 675 <p>
 676
 677 </p>
 678 <pre class="programlisting"># This is the start of a comment.  The next line
 679 # is a new comment, even though it is logically
 680 # part of the previous comment.
 681 </pre>
 682 <p>
 683
 684           </p>
 685 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 686 <h3 class="title">Warning</h3>
 687 <p>
 688               You cannot use the semicolon (`;') character
 689               to start a comment such as you would in a zone file. The
 690               semicolon indicates the end of a configuration
 691               statement.
 692             </p>
 693 </div>
 694 </div>
 695 </div>
 696 </div>
 697 <div class="sect1" lang="en">
 698 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 699 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 700 <p>
 701         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 702         statements and comments.
 703         Statements end with a semicolon. Statements and comments are the
 704         only elements that can appear without enclosing braces. Many
 705         statements contain a block of sub-statements, which are also
 706         terminated with a semicolon.
 707       </p>
 708 <p>
 709         The following statements are supported:
 710       </p>
 711 <div class="informaltable"><table border="1">
 712 <colgroup>
 713 <col>
 714 <col>
 715 </colgroup>
 716 <tbody>
 717 <tr>
 718 <td>
 719                 <p><span><strong class="command">acl</strong></span></p>
 720               </td>
 721 <td>
 722                 <p>
 723                   defines a named IP address
 724                   matching list, for access control and other uses.
 725                 </p>
 726               </td>
 727 </tr>
 728 <tr>
 729 <td>
 730                 <p><span><strong class="command">controls</strong></span></p>
 731               </td>
 732 <td>
 733                 <p>
 734                   declares control channels to be used
 735                   by the <span><strong class="command">rndc</strong></span> utility.
 736                 </p>
 737               </td>
 738 </tr>
 739 <tr>
 740 <td>
 741                 <p><span><strong class="command">include</strong></span></p>
 742               </td>
 743 <td>
 744                 <p>
 745                   includes a file.
 746                 </p>
 747               </td>
 748 </tr>
 749 <tr>
 750 <td>
 751                 <p><span><strong class="command">key</strong></span></p>
 752               </td>
 753 <td>
 754                 <p>
 755                   specifies key information for use in
 756                   authentication and authorization using TSIG.
 757                 </p>
 758               </td>
 759 </tr>
 760 <tr>
 761 <td>
 762                 <p><span><strong class="command">logging</strong></span></p>
 763               </td>
 764 <td>
 765                 <p>
 766                   specifies what the server logs, and where
 767                   the log messages are sent.
 768                 </p>
 769               </td>
 770 </tr>
 771 <tr>
 772 <td>
 773                 <p><span><strong class="command">lwres</strong></span></p>
 774               </td>
 775 <td>
 776                 <p>
 777                   configures <span><strong class="command">named</strong></span> to
 778                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 779                 </p>
 780               </td>
 781 </tr>
 782 <tr>
 783 <td>
 784                 <p><span><strong class="command">masters</strong></span></p>
 785               </td>
 786 <td>
 787                 <p>
 788                   defines a named masters list for
 789                   inclusion in stub and slave zones'
 790                   <span><strong class="command">masters</strong></span> or
 791                   <span><strong class="command">also-notify</strong></span> lists.
 792                 </p>
 793               </td>
 794 </tr>
 795 <tr>
 796 <td>
 797                 <p><span><strong class="command">options</strong></span></p>
 798               </td>
 799 <td>
 800                 <p>
 801                   controls global server configuration
 802                   options and sets defaults for other statements.
 803                 </p>
 804               </td>
 805 </tr>
 806 <tr>
 807 <td>
 808                 <p><span><strong class="command">server</strong></span></p>
 809               </td>
 810 <td>
 811                 <p>
 812                   sets certain configuration options on
 813                   a per-server basis.
 814                 </p>
 815               </td>
 816 </tr>
 817 <tr>
 818 <td>
 819                 <p><span><strong class="command">statistics-channels</strong></span></p>
 820               </td>
 821 <td>
 822                 <p>
 823                   declares communication channels to get access to
 824                   <span><strong class="command">named</strong></span> statistics.
 825                 </p>
 826               </td>
 827 </tr>
 828 <tr>
 829 <td>
 830                 <p><span><strong class="command">trusted-keys</strong></span></p>
 831               </td>
 832 <td>
 833                 <p>
 834                   defines trusted DNSSEC keys.
 835                 </p>
 836               </td>
 837 </tr>
 838 <tr>
 839 <td>
 840                 <p><span><strong class="command">managed-keys</strong></span></p>
 841               </td>
 842 <td>
 843                 <p>
 844                   lists DNSSEC keys to be kept up to date
 845                   using RFC 5011 trust anchor maintenance.
 846                 </p>
 847               </td>
 848 </tr>
 849 <tr>
 850 <td>
 851                 <p><span><strong class="command">view</strong></span></p>
 852               </td>
 853 <td>
 854                 <p>
 855                   defines a view.
 856                 </p>
 857               </td>
 858 </tr>
 859 <tr>
 860 <td>
 861                 <p><span><strong class="command">zone</strong></span></p>
 862               </td>
 863 <td>
 864                 <p>
 865                   defines a zone.
 866                 </p>
 867               </td>
 868 </tr>
 869 </tbody>
 870 </table></div>
 871 <p>
 872         The <span><strong class="command">logging</strong></span> and
 873         <span><strong class="command">options</strong></span> statements may only occur once
 874         per
 875         configuration.
 876       </p>
 877 <div class="sect2" lang="en">
 878 <div class="titlepage"><div><div><h3 class="title">
 879 <a name="id2574009"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 880 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 881     address_match_list
 882 };
 883 </pre>
 884 </div>
 885 <div class="sect2" lang="en">
 886 <div class="titlepage"><div><div><h3 class="title">
 887 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 888           Usage</h3></div></div></div>
 889 <p>
 890           The <span><strong class="command">acl</strong></span> statement assigns a symbolic
 891           name to an address match list. It gets its name from a primary
 892           use of address match lists: Access Control Lists (ACLs).
 893         </p>
 894 <p>
 895           The following ACLs are built-in:
 896         </p>
 897 <div class="informaltable"><table border="1">
 898 <colgroup>
 899 <col>
 900 <col>
 901 </colgroup>
 902 <tbody>
 903 <tr>
 904 <td>
 905                   <p><span><strong class="command">any</strong></span></p>
 906                 </td>
 907 <td>
 908                   <p>
 909                     Matches all hosts.
 910                   </p>
 911                 </td>
 912 </tr>
 913 <tr>
 914 <td>
 915                   <p><span><strong class="command">none</strong></span></p>
 916                 </td>
 917 <td>
 918                   <p>
 919                     Matches no hosts.
 920                   </p>
 921                 </td>
 922 </tr>
 923 <tr>
 924 <td>
 925                   <p><span><strong class="command">localhost</strong></span></p>
 926                 </td>
 927 <td>
 928                   <p>
 929                     Matches the IPv4 and IPv6 addresses of all network
 930                     interfaces on the system.  When addresses are
 931                     added or removed, the <span><strong class="command">localhost</strong></span>
 932                     ACL element is updated to reflect the changes.
 933                   </p>
 934                 </td>
 935 </tr>
 936 <tr>
 937 <td>
 938                   <p><span><strong class="command">localnets</strong></span></p>
 939                 </td>
 940 <td>
 941                   <p>
 942                     Matches any host on an IPv4 or IPv6 network
 943                     for which the system has an interface.
 944                     When addresses are added or removed,
 945                     the <span><strong class="command">localnets</strong></span>
 946                     ACL element is updated to reflect the changes.
 947                     Some systems do not provide a way to determine the prefix
 948                     lengths of
 949                     local IPv6 addresses.
 950                     In such a case, <span><strong class="command">localnets</strong></span>
 951                     only matches the local
 952                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 953                   </p>
 954                 </td>
 955 </tr>
 956 </tbody>
 957 </table></div>
 958 <p>
 959           When <acronym class="acronym">BIND</acronym> 9 is built with GeoIP support,
 960           ACLs can also be used for geographic access restrictions.
 961           This is done by specifying an ACL element of the form:
 962           <span><strong class="command">geoip [<span class="optional">db <em class="replaceable"><code>database</code></em></span>] <em class="replaceable"><code>field</code></em> <em class="replaceable"><code>value</code></em></strong></span>
 963         </p>
 964 <p>
 965           The <em class="replaceable"><code>field</code></em> indicates which field
 966           to search for a match.  Available fields are "country",
 967           "region", "city", "continent", "postal" (postal code),
 968           "metro" (metro code), "area" (area code), "tz" (timezone),
 969           "isp", "org", "asnum", "domain" and "netspeed".
 970         </p>
 971 <p>
 972           <em class="replaceable"><code>value</code></em> is the value to search
 973           for within the database.  A string may be quoted if it
 974           contains spaces or other special characters.  If this is
 975           an "asnum" search, then the leading "ASNNNN" string can be
 976           used, otherwise the full description must be used (e.g.
 977           "ASNNNN Example Company Name").  If this is a "country"
 978           search and the string is two characters long, then it must
 979           be a standard ISO-3166-1 two-letter country code, and if it
 980           is three characters long then it must be an ISO-3166-1
 981           three-letter country code; otherwise it is the full name
 982           of the country.  Similarly, if this is a "region" search
 983           and the string is two characters long, then it must be a
 984           standard two-letter state or province abbreviation;
 985           otherwise it is the full name of the state or province.
 986         </p>
 987 <p>
 988           The <em class="replaceable"><code>database</code></em> field indicates which
 989           GeoIP database to search for a match.  In most cases this is
 990           unnecessary, because most search fields can only be found in
 991           a single database.  However, searches for country can be
 992           answered from the "city", "region", or "country" databases,
 993           and searches for region (i.e., state or province) can be
 994           answered from the "city" or "region" databases.  For these
 995           search types, specifying a <em class="replaceable"><code>database</code></em>
 996           will force the query to be answered from that database and no
 997           other.  If <em class="replaceable"><code>database</code></em> is not
 998           specified, then these queries will be answered from the "city",
 999           database if it is installed, or the "region" database if it is
1000           installed, or the "country" database, in that order.
1001         </p>
1002 <p>
1003           Some example GeoIP ACLs:
1004         </p>
1005 <pre class="programlisting">geoip country US;
1006 geoip country JAP;
1007 geoip db country country Canada;
1008 geoip db region region WA;
1009 geoip city "San Francisco";
1010 geoip region Oklahoma;
1011 geoip postal 95062;
1012 geoip tz "America/Los_Angeles";
1013 geoip org "Internet Systems Consortium";
1014 </pre>
1015 </div>
1016 <div class="sect2" lang="en">
1017 <div class="titlepage"><div><div><h3 class="title">
1018 <a name="id2574321"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
1019 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
1020    [ inet ( ip_addr | * ) [ port ip_port ]
1021                 allow { <em class="replaceable"><code> address_match_list </code></em> }
1022                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
1023    [ inet ...; ]
1024    [ unix <em class="replaceable"><code>path</code></em> perm <em class="replaceable"><code>number</code></em> owner <em class="replaceable"><code>number</code></em> group <em class="replaceable"><code>number</code></em>
1025      keys { <em class="replaceable"><code>key_list</code></em> }; ]
1026    [ unix ...; ]
1027 };
1028 </pre>
1029 </div>
1030 <div class="sect2" lang="en">
1031 <div class="titlepage"><div><div><h3 class="title">
1032 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
1033           Usage</h3></div></div></div>
1034 <p>
1035           The <span><strong class="command">controls</strong></span> statement declares control
1036           channels to be used by system administrators to control the
1037           operation of the name server. These control channels are
1038           used by the <span><strong class="command">rndc</strong></span> utility to send
1039           commands to and retrieve non-DNS results from a name server.
1040         </p>
1041 <p>
1042           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
1043           listening at the specified <span><strong class="command">ip_port</strong></span> on the
1044           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
1045           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
1046           interpreted as the IPv4 wildcard address; connections will be
1047           accepted on any of the system's IPv4 addresses.
1048           To listen on the IPv6 wildcard address,
1049           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
1050           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
1051           using the loopback address (<code class="literal">127.0.0.1</code>
1052           or <code class="literal">::1</code>) is recommended for maximum security.
1053         </p>
1054 <p>
1055           If no port is specified, port 953 is used. The asterisk
1056           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
1057         </p>
1058 <p>
1059           The ability to issue commands over the control channel is
1060           restricted by the <span><strong class="command">allow</strong></span> and
1061           <span><strong class="command">keys</strong></span> clauses.
1062           Connections to the control channel are permitted based on the
1063           <span><strong class="command">address_match_list</strong></span>.  This is for simple
1064           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
1065           elements of the <span><strong class="command">address_match_list</strong></span>
1066           are ignored.
1067         </p>
1068 <p>
1069           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
1070           socket listening at the specified path in the file system.
1071           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
1072           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
1073           Note on some platforms (SunOS and Solaris) the permissions
1074           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
1075           as the permissions on the socket itself are ignored.
1076         </p>
1077 <p>
1078           The primary authorization mechanism of the command
1079           channel is the <span><strong class="command">key_list</strong></span>, which
1080           contains a list of <span><strong class="command">key_id</strong></span>s.
1081           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
1082           is authorized to execute commands over the control channel.
1083           See <a href="Bv9ARM.ch03.html#rndc">Remote Name Daemon Control application</a> in <a href="Bv9ARM.ch03.html#admin_tools" title="Administrative Tools">the section called &#8220;Administrative Tools&#8221;</a>)
1084           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
1085         </p>
1086 <p>
1087           If no <span><strong class="command">controls</strong></span> statement is present,
1088           <span><strong class="command">named</strong></span> will set up a default
1089           control channel listening on the loopback address 127.0.0.1
1090           and its IPv6 counterpart ::1.
1091           In this case, and also when the <span><strong class="command">controls</strong></span> statement
1092           is present but does not have a <span><strong class="command">keys</strong></span> clause,
1093           <span><strong class="command">named</strong></span> will attempt to load the command channel key
1094           from the file <code class="filename">rndc.key</code> in
1095           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1096           was specified as when <acronym class="acronym">BIND</acronym> was built).
1097           To create a <code class="filename">rndc.key</code> file, run
1098           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1099         </p>
1100 <p>
1101           The <code class="filename">rndc.key</code> feature was created to
1102           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1103           which did not have digital signatures on its command channel
1104           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
1105
1106           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1107           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1108           and still have <span><strong class="command">rndc</strong></span> work the same way
1109           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
1110           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1111           installed.
1112         </p>
1113 <p>
1114           Since the <code class="filename">rndc.key</code> feature
1115           is only intended to allow the backward-compatible usage of
1116           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1117           feature does not
1118           have a high degree of configurability.  You cannot easily change
1119           the key name or the size of the secret, so you should make a
1120           <code class="filename">rndc.conf</code> with your own key if you
1121           wish to change
1122           those things.  The <code class="filename">rndc.key</code> file
1123           also has its
1124           permissions set such that only the owner of the file (the user that
1125           <span><strong class="command">named</strong></span> is running as) can access it.
1126           If you
1127           desire greater flexibility in allowing other users to access
1128           <span><strong class="command">rndc</strong></span> commands, then you need to create
1129           a
1130           <code class="filename">rndc.conf</code> file and make it group
1131           readable by a group
1132           that contains the users who should have access.
1133         </p>
1134 <p>
1135           To disable the command channel, use an empty
1136           <span><strong class="command">controls</strong></span> statement:
1137           <span><strong class="command">controls { };</strong></span>.
1138         </p>
1139 </div>
1140 <div class="sect2" lang="en">
1141 <div class="titlepage"><div><div><h3 class="title">
1142 <a name="id2574748"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1143 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1144 </div>
1145 <div class="sect2" lang="en">
1146 <div class="titlepage"><div><div><h3 class="title">
1147 <a name="id2574765"></a><span><strong class="command">include</strong></span> Statement Definition and
1148           Usage</h3></div></div></div>
1149 <p>
1150           The <span><strong class="command">include</strong></span> statement inserts the
1151           specified file at the point where the <span><strong class="command">include</strong></span>
1152           statement is encountered. The <span><strong class="command">include</strong></span>
1153                 statement facilitates the administration of configuration
1154           files
1155           by permitting the reading or writing of some things but not
1156           others. For example, the statement could include private keys
1157           that are readable only by the name server.
1158         </p>
1159 </div>
1160 <div class="sect2" lang="en">
1161 <div class="titlepage"><div><div><h3 class="title">
1162 <a name="id2574789"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1163 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1164     algorithm <em class="replaceable"><code>string</code></em>;
1165     secret <em class="replaceable"><code>string</code></em>;
1166 };
1167 </pre>
1168 </div>
1169 <div class="sect2" lang="en">
1170 <div class="titlepage"><div><div><h3 class="title">
1171 <a name="id2574812"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1172 <p>
1173           The <span><strong class="command">key</strong></span> statement defines a shared
1174           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1175           or the command channel
1176           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1177           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1178           Usage&#8221;</a>).
1179         </p>
1180 <p>
1181           The <span><strong class="command">key</strong></span> statement can occur at the
1182           top level
1183           of the configuration file or inside a <span><strong class="command">view</strong></span>
1184           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1185           statements can be used in all views.  Keys intended for use in
1186           a <span><strong class="command">controls</strong></span> statement
1187           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1188           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1189           Usage&#8221;</a>)
1190           must be defined at the top level.
1191         </p>
1192 <p>
1193           The <em class="replaceable"><code>key_id</code></em>, also known as the
1194           key name, is a domain name uniquely identifying the key. It can
1195           be used in a <span><strong class="command">server</strong></span>
1196           statement to cause requests sent to that
1197           server to be signed with this key, or in address match lists to
1198           verify that incoming requests have been signed with a key
1199           matching this name, algorithm, and secret.
1200         </p>
1201 <p>
1202           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1203           that specifies a security/authentication algorithm.  Named
1204           supports <code class="literal">hmac-md5</code>,
1205           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1206           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1207           and <code class="literal">hmac-sha512</code> TSIG authentication.
1208           Truncated hashes are supported by appending the minimum
1209           number of required bits preceded by a dash, e.g.
1210           <code class="literal">hmac-sha1-80</code>.  The
1211           <em class="replaceable"><code>secret_string</code></em> is the secret
1212           to be used by the algorithm, and is treated as a base-64
1213           encoded string.
1214         </p>
1215 </div>
1216 <div class="sect2" lang="en">
1217 <div class="titlepage"><div><div><h3 class="title">
1218 <a name="id2574903"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1219 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1220    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1221      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1222          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1223          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size_spec</code></em> ]
1224        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1225        | <span><strong class="command">stderr</strong></span>
1226        | <span><strong class="command">null</strong></span> );
1227      [ <span><strong class="command">severity</strong></span> (<code class="option">critical</code> | <code class="option">error</code> | <code class="option">warning</code> | <code class="option">notice</code> |
1228                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1229      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1230      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1231      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1232    }; ]
1233    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1234      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1235    }; ]
1236    ...
1237 };
1238 </pre>
1239 </div>
1240 <div class="sect2" lang="en">
1241 <div class="titlepage"><div><div><h3 class="title">
1242 <a name="id2575029"></a><span><strong class="command">logging</strong></span> Statement Definition and
1243           Usage</h3></div></div></div>
1244 <p>
1245           The <span><strong class="command">logging</strong></span> statement configures a
1246           wide
1247           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1248           associates output methods, format options and severity levels with
1249           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1250           to select how various classes of messages are logged.
1251         </p>
1252 <p>
1253           Only one <span><strong class="command">logging</strong></span> statement is used to
1254           define
1255           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1256           the logging configuration will be:
1257         </p>
1258 <pre class="programlisting">logging {
1259      category default { default_syslog; default_debug; };
1260      category unmatched { null; };
1261 };
1262 </pre>
1263 <p>
1264           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1265           is only established when
1266           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1267           established as soon as the <span><strong class="command">logging</strong></span>
1268           statement
1269           was parsed. When the server is starting up, all logging messages
1270           regarding syntax errors in the configuration file go to the default
1271           channels, or to standard error if the "<code class="option">-g</code>" option
1272           was specified.
1273         </p>
1274 <div class="sect3" lang="en">
1275 <div class="titlepage"><div><div><h4 class="title">
1276 <a name="id2575081"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1277 <p>
1278             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1279             you can make as many of them as you want.
1280           </p>
1281 <p>
1282             Every channel definition must include a destination clause that
1283             says whether messages selected for the channel go to a file, to a
1284             particular syslog facility, to the standard error stream, or are
1285             discarded. It can optionally also limit the message severity level
1286             that will be accepted by the channel (the default is
1287             <span><strong class="command">info</strong></span>), and whether to include a
1288             <span><strong class="command">named</strong></span>-generated time stamp, the
1289             category name
1290             and/or severity level (the default is not to include any).
1291           </p>
1292 <p>
1293             The <span><strong class="command">null</strong></span> destination clause
1294             causes all messages sent to the channel to be discarded;
1295             in that case, other options for the channel are meaningless.
1296           </p>
1297 <p>
1298             The <span><strong class="command">file</strong></span> destination clause directs
1299             the channel
1300             to a disk file.  It can include limitations
1301             both on how large the file is allowed to become, and how many
1302             versions
1303             of the file will be saved each time the file is opened.
1304           </p>
1305 <p>
1306             If you use the <span><strong class="command">versions</strong></span> log file
1307             option, then
1308             <span><strong class="command">named</strong></span> will retain that many backup
1309             versions of the file by
1310             renaming them when opening.  For example, if you choose to keep
1311             three old versions
1312             of the file <code class="filename">lamers.log</code>, then just
1313             before it is opened
1314             <code class="filename">lamers.log.1</code> is renamed to
1315             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1316             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1317             renamed to <code class="filename">lamers.log.0</code>.
1318             You can say <span><strong class="command">versions unlimited</strong></span> to
1319             not limit
1320             the number of versions.
1321             If a <span><strong class="command">size</strong></span> option is associated with
1322             the log file,
1323             then renaming is only done when the file being opened exceeds the
1324             indicated size.  No backup versions are kept by default; any
1325             existing
1326             log file is simply appended.
1327           </p>
1328 <p>
1329             The <span><strong class="command">size</strong></span> option for files is used
1330             to limit log
1331             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1332             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1333             associated with it.  If backup versions are kept, the files are
1334             rolled as
1335             described above and a new one begun.  If there is no
1336             <span><strong class="command">versions</strong></span> option, no more data will
1337             be written to the log
1338             until some out-of-band mechanism removes or truncates the log to
1339             less than the
1340             maximum size.  The default behavior is not to limit the size of
1341             the
1342             file.
1343           </p>
1344 <p>
1345             Example usage of the <span><strong class="command">size</strong></span> and
1346             <span><strong class="command">versions</strong></span> options:
1347           </p>
1348 <pre class="programlisting">channel an_example_channel {
1349     file "example.log" versions 3 size 20m;
1350     print-time yes;
1351     print-category yes;
1352 };
1353 </pre>
1354 <p>
1355             The <span><strong class="command">syslog</strong></span> destination clause
1356             directs the
1357             channel to the system log.  Its argument is a
1358             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1359             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1360             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1361             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1362             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1363             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1364             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1365             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1366             <span><strong class="command">local7</strong></span>, however not all facilities
1367             are supported on
1368             all operating systems.
1369             How <span><strong class="command">syslog</strong></span> will handle messages
1370             sent to
1371             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1372             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1373             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1374             then this clause is silently ignored.
1375           </p>
1376 <p>
1377             On Windows machines syslog messages are directed to the EventViewer.
1378           </p>
1379 <p>
1380             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1381             "priorities", except that they can also be used if you are writing
1382             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1383             Messages which are not at least of the severity level given will
1384             not be selected for the channel; messages of higher severity
1385             levels
1386             will be accepted.
1387           </p>
1388 <p>
1389             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1390             will also determine what eventually passes through. For example,
1391             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1392             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1393             cause messages of severity <span><strong class="command">info</strong></span> and
1394             <span><strong class="command">notice</strong></span> to
1395             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1396             messages of only <span><strong class="command">warning</strong></span> or higher,
1397             then <span><strong class="command">syslogd</strong></span> would
1398             print all messages it received from the channel.
1399           </p>
1400 <p>
1401             The <span><strong class="command">stderr</strong></span> destination clause
1402             directs the
1403             channel to the server's standard error stream.  This is intended
1404             for
1405             use when the server is running as a foreground process, for
1406             example
1407             when debugging a configuration.
1408           </p>
1409 <p>
1410             The server can supply extensive debugging information when
1411             it is in debugging mode. If the server's global debug level is
1412             greater
1413             than zero, then debugging mode will be active. The global debug
1414             level is set either by starting the <span><strong class="command">named</strong></span> server
1415             with the <code class="option">-d</code> flag followed by a positive integer,
1416             or by running <span><strong class="command">rndc trace</strong></span>.
1417             The global debug level
1418             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1419 notrace</strong></span>. All debugging messages in the server have a debug
1420             level, and higher debug levels give more detailed output. Channels
1421             that specify a specific debug severity, for example:
1422           </p>
1423 <pre class="programlisting">channel specific_debug_level {
1424     file "foo";
1425     severity debug 3;
1426 };
1427 </pre>
1428 <p>
1429             will get debugging output of level 3 or less any time the
1430             server is in debugging mode, regardless of the global debugging
1431             level. Channels with <span><strong class="command">dynamic</strong></span>
1432             severity use the
1433             server's global debug level to determine what messages to print.
1434           </p>
1435 <p>
1436             If <span><strong class="command">print-time</strong></span> has been turned on,
1437             then
1438             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1439             be specified for a <span><strong class="command">syslog</strong></span> channel,
1440             but is usually
1441             pointless since <span><strong class="command">syslog</strong></span> also logs
1442             the date and
1443             time. If <span><strong class="command">print-category</strong></span> is
1444             requested, then the
1445             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1446             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1447             be used in any combination, and will always be printed in the
1448             following
1449             order: time, category, severity. Here is an example where all
1450             three <span><strong class="command">print-</strong></span> options
1451             are on:
1452           </p>
1453 <p>
1454             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1455           </p>
1456 <p>
1457             There are four predefined channels that are used for
1458             <span><strong class="command">named</strong></span>'s default logging as follows.
1459             How they are
1460             used is described in <a href="Bv9ARM.ch06.html#the_category_phrase" title="The category Phrase">the section called &#8220;The <span><strong class="command">category</strong></span> Phrase&#8221;</a>.
1461           </p>
1462 <pre class="programlisting">channel default_syslog {
1463     // send to syslog's daemon facility
1464     syslog daemon;
1465     // only send priority info and higher
1466     severity info;
1467
1468 channel default_debug {
1469     // write to named.run in the working directory
1470     // Note: stderr is used instead of "named.run" if
1471     // the server is started with the '-f' option.
1472     file "named.run";
1473     // log at the server's current debug level
1474     severity dynamic;
1475 };
1476
1477 channel default_stderr {
1478     // writes to stderr
1479     stderr;
1480     // only send priority info and higher
1481     severity info;
1482 };
1483
1484 channel null {
1485    // toss anything sent to this channel
1486    null;
1487 };
1488 </pre>
1489 <p>
1490             The <span><strong class="command">default_debug</strong></span> channel has the
1491             special
1492             property that it only produces output when the server's debug
1493             level is
1494             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1495             in the server's working directory.
1496           </p>
1497 <p>
1498             For security reasons, when the "<code class="option">-u</code>"
1499             command line option is used, the <code class="filename">named.run</code> file
1500             is created only after <span><strong class="command">named</strong></span> has
1501             changed to the
1502             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1503             starting up and still running as root is discarded.  If you need
1504             to capture this output, you must run the server with the "<code class="option">-g</code>"
1505             option and redirect standard error to a file.
1506           </p>
1507 <p>
1508             Once a channel is defined, it cannot be redefined. Thus you
1509             cannot alter the built-in channels directly, but you can modify
1510             the default logging by pointing categories at channels you have
1511             defined.
1512           </p>
1513 </div>
1514 <div class="sect3" lang="en">
1515 <div class="titlepage"><div><div><h4 class="title">
1516 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1517 <p>
1518             There are many categories, so you can send the logs you want
1519             to see wherever you want, without seeing logs you don't want. If
1520             you don't specify a list of channels for a category, then log
1521             messages
1522             in that category will be sent to the <span><strong class="command">default</strong></span> category
1523             instead. If you don't specify a default category, the following
1524             "default default" is used:
1525           </p>
1526 <pre class="programlisting">category default { default_syslog; default_debug; };
1527 </pre>
1528 <p>
1529             As an example, let's say you want to log security events to
1530             a file, but you also want keep the default logging behavior. You'd
1531             specify the following:
1532           </p>
1533 <pre class="programlisting">channel my_security_channel {
1534     file "my_security_file";
1535     severity info;
1536 };
1537 category security {
1538     my_security_channel;
1539     default_syslog;
1540     default_debug;
1541 };</pre>
1542 <p>
1543             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1544           </p>
1545 <pre class="programlisting">category xfer-out { null; };
1546 category notify { null; };
1547 </pre>
1548 <p>
1549             Following are the available categories and brief descriptions
1550             of the types of log information they contain. More
1551             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1552           </p>
1553 <div class="informaltable"><table border="1">
1554 <colgroup>
1555 <col>
1556 <col>
1557 </colgroup>
1558 <tbody>
1559 <tr>
1560 <td>
1561                     <p><span><strong class="command">default</strong></span></p>
1562                   </td>
1563 <td>
1564                     <p>
1565                       The default category defines the logging
1566                       options for those categories where no specific
1567                       configuration has been
1568                       defined.
1569                     </p>
1570                   </td>
1571 </tr>
1572 <tr>
1573 <td>
1574                     <p><span><strong class="command">general</strong></span></p>
1575                   </td>
1576 <td>
1577                     <p>
1578                       The catch-all. Many things still aren't
1579                       classified into categories, and they all end up here.
1580                     </p>
1581                   </td>
1582 </tr>
1583 <tr>
1584 <td>
1585                     <p><span><strong class="command">database</strong></span></p>
1586                   </td>
1587 <td>
1588                     <p>
1589                       Messages relating to the databases used
1590                       internally by the name server to store zone and cache
1591                       data.
1592                     </p>
1593                   </td>
1594 </tr>
1595 <tr>
1596 <td>
1597                     <p><span><strong class="command">security</strong></span></p>
1598                   </td>
1599 <td>
1600                     <p>
1601                       Approval and denial of requests.
1602                     </p>
1603                   </td>
1604 </tr>
1605 <tr>
1606 <td>
1607                     <p><span><strong class="command">config</strong></span></p>
1608                   </td>
1609 <td>
1610                     <p>
1611                       Configuration file parsing and processing.
1612                     </p>
1613                   </td>
1614 </tr>
1615 <tr>
1616 <td>
1617                     <p><span><strong class="command">resolver</strong></span></p>
1618                   </td>
1619 <td>
1620                     <p>
1621                       DNS resolution, such as the recursive
1622                       lookups performed on behalf of clients by a caching name
1623                       server.
1624                     </p>
1625                   </td>
1626 </tr>
1627 <tr>
1628 <td>
1629                     <p><span><strong class="command">xfer-in</strong></span></p>
1630                   </td>
1631 <td>
1632                     <p>
1633                       Zone transfers the server is receiving.
1634                     </p>
1635                   </td>
1636 </tr>
1637 <tr>
1638 <td>
1639                     <p><span><strong class="command">xfer-out</strong></span></p>
1640                   </td>
1641 <td>
1642                     <p>
1643                       Zone transfers the server is sending.
1644                     </p>
1645                   </td>
1646 </tr>
1647 <tr>
1648 <td>
1649                     <p><span><strong class="command">notify</strong></span></p>
1650                   </td>
1651 <td>
1652                     <p>
1653                       The NOTIFY protocol.
1654                     </p>
1655                   </td>
1656 </tr>
1657 <tr>
1658 <td>
1659                     <p><span><strong class="command">client</strong></span></p>
1660                   </td>
1661 <td>
1662                     <p>
1663                       Processing of client requests.
1664                     </p>
1665                   </td>
1666 </tr>
1667 <tr>
1668 <td>
1669                     <p><span><strong class="command">unmatched</strong></span></p>
1670                   </td>
1671 <td>
1672                     <p>
1673                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1674                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1675                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1676                       This category is best sent to a file or stderr, by
1677                       default it is sent to
1678                       the <span><strong class="command">null</strong></span> channel.
1679                     </p>
1680                   </td>
1681 </tr>
1682 <tr>
1683 <td>
1684                     <p><span><strong class="command">network</strong></span></p>
1685                   </td>
1686 <td>
1687                     <p>
1688                       Network operations.
1689                     </p>
1690                   </td>
1691 </tr>
1692 <tr>
1693 <td>
1694                     <p><span><strong class="command">update</strong></span></p>
1695                   </td>
1696 <td>
1697                     <p>
1698                       Dynamic updates.
1699                     </p>
1700                   </td>
1701 </tr>
1702 <tr>
1703 <td>
1704                     <p><span><strong class="command">update-security</strong></span></p>
1705                   </td>
1706 <td>
1707                     <p>
1708                       Approval and denial of update requests.
1709                     </p>
1710                   </td>
1711 </tr>
1712 <tr>
1713 <td>
1714                     <p><span><strong class="command">queries</strong></span></p>
1715                   </td>
1716 <td>
1717                     <p>
1718                       Specify where queries should be logged to.
1719                     </p>
1720                     <p>
1721                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1722                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1723                       specified.
1724                     </p>
1725
1726                     <p>
1727                       The query log entry reports the client's IP
1728                       address and port number, and the query name,
1729                       class and type.  Next it reports whether the
1730                       Recursion Desired flag was set (+ if set, -
1731                       if not set), if the query was signed (S),
1732                       EDNS was in use (E), if TCP was used (T), if
1733                       DO (DNSSEC Ok) was set (D), or if CD (Checking
1734                       Disabled) was set (C).  After this the
1735                       destination address the query was sent to is
1736                       reported.
1737                     </p>
1738
1739                     <p>
1740                       <code class="computeroutput">client 127.0.0.1#62536 (www.example.com): query: www.example.com IN AAAA +SE</code>
1741                     </p>
1742                     <p>
1743                       <code class="computeroutput">client ::1#62537 (www.example.net): query: www.example.net IN AAAA -SE</code>
1744                     </p>
1745                     <p>
1746                       (The first part of this log message, showing the
1747                       client address/port number and query name, is
1748                       repeated in all subsequent log messages related
1749                       to the same query.)
1750                     </p>
1751                   </td>
1752 </tr>
1753 <tr>
1754 <td>
1755                     <p><span><strong class="command">query-errors</strong></span></p>
1756                   </td>
1757 <td>
1758                     <p>
1759                       Information about queries that resulted in some
1760                       failure.
1761                     </p>
1762                   </td>
1763 </tr>
1764 <tr>
1765 <td>
1766                     <p><span><strong class="command">dispatch</strong></span></p>
1767                   </td>
1768 <td>
1769                     <p>
1770                       Dispatching of incoming packets to the
1771                       server modules where they are to be processed.
1772                     </p>
1773                   </td>
1774 </tr>
1775 <tr>
1776 <td>
1777                     <p><span><strong class="command">dnssec</strong></span></p>
1778                   </td>
1779 <td>
1780                     <p>
1781                       DNSSEC and TSIG protocol processing.
1782                     </p>
1783                   </td>
1784 </tr>
1785 <tr>
1786 <td>
1787                     <p><span><strong class="command">lame-servers</strong></span></p>
1788                   </td>
1789 <td>
1790                     <p>
1791                       Lame servers.  These are misconfigurations
1792                       in remote servers, discovered by BIND 9 when trying to
1793                       query those servers during resolution.
1794                     </p>
1795                   </td>
1796 </tr>
1797 <tr>
1798 <td>
1799                     <p><span><strong class="command">delegation-only</strong></span></p>
1800                   </td>
1801 <td>
1802                     <p>
1803                       Delegation only.  Logs queries that have been
1804                       forced to NXDOMAIN as the result of a
1805                       delegation-only zone or a
1806                       <span><strong class="command">delegation-only</strong></span> in a
1807                       forward, hint or stub zone declaration.
1808                     </p>
1809                   </td>
1810 </tr>
1811 <tr>
1812 <td>
1813                     <p><span><strong class="command">edns-disabled</strong></span></p>
1814                   </td>
1815 <td>
1816                     <p>
1817                       Log queries that have been forced to use plain
1818                       DNS due to timeouts.  This is often due to
1819                       the remote servers not being RFC 1034 compliant
1820                       (not always returning FORMERR or similar to
1821                       EDNS queries and other extensions to the DNS
1822                       when they are not understood).  In other words, this is
1823                       targeted at servers that fail to respond to
1824                       DNS queries that they don't understand.
1825                     </p>
1826                     <p>
1827                       Note: the log message can also be due to
1828                       packet loss.  Before reporting servers for
1829                       non-RFC 1034 compliance they should be re-tested
1830                       to determine the nature of the non-compliance.
1831                       This testing should prevent or reduce the
1832                       number of false-positive reports.
1833                     </p>
1834                     <p>
1835                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1836                       treating such timeouts as due to RFC 1034 non
1837                       compliance and start treating it as plain
1838                       packet loss.  Falsely classifying packet
1839                       loss as due to RFC 1034 non compliance impacts
1840                       on DNSSEC validation which requires EDNS for
1841                       the DNSSEC records to be returned.
1842                     </p>
1843                   </td>
1844 </tr>
1845 <tr>
1846 <td>
1847                     <p><span><strong class="command">RPZ</strong></span></p>
1848                   </td>
1849 <td>
1850                     <p>
1851                       Information about errors in response policy zone files,
1852                       rewritten responses, and at the highest
1853                       <span><strong class="command">debug</strong></span> levels, mere rewriting
1854                       attempts.
1855                     </p>
1856                   </td>
1857 </tr>
1858 <tr>
1859 <td>
1860                     <p><span><strong class="command">rate-limit</strong></span></p>
1861                   </td>
1862 <td>
1863                     <p>
1864                       The start, periodic, and final notices of the
1865                       rate limiting of a stream of responses are logged at
1866                       <span><strong class="command">info</strong></span> severity in this category.
1867                       These messages include a hash value of the domain name
1868                       of the response and the name itself,
1869                       except when there is insufficient memory to record
1870                       the name for the final notice
1871                       The final notice is normally delayed until about one
1872                       minute after rate limit stops.
1873                       A lack of memory can hurry the final notice,
1874                       in which case it starts with an asterisk (*).
1875                       Various internal events are logged at debug 1 level
1876                       and higher.
1877                     </p>
1878                     <p>
1879                       Rate limiting of individual requests
1880                       is logged in the <span><strong class="command">query-errors</strong></span> category.
1881                     </p>
1882                   </td>
1883 </tr>
1884 <tr>
1885 <td>
1886                     <p><span><strong class="command">cname</strong></span></p>
1887                   </td>
1888 <td>
1889                     <p>
1890                       Logs nameservers that are skipped due to them being
1891                       a CNAME rather than A / AAAA records.
1892                     </p>
1893                   </td>
1894 </tr>
1895 </tbody>
1896 </table></div>
1897 </div>
1898 <div class="sect3" lang="en">
1899 <div class="titlepage"><div><div><h4 class="title">
1900 <a name="id2576732"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1901 <p>
1902             The <span><strong class="command">query-errors</strong></span> category is
1903             specifically intended for debugging purposes: To identify
1904             why and how specific queries result in responses which
1905             indicate an error.
1906             Messages of this category are therefore only logged
1907             with <span><strong class="command">debug</strong></span> levels.
1908           </p>
1909 <p>
1910             At the debug levels of 1 or higher, each response with the
1911             rcode of SERVFAIL is logged as follows:
1912           </p>
1913 <p>
1914             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1915           </p>
1916 <p>
1917             This means an error resulting in SERVFAIL was
1918             detected at line 3880 of source file
1919             <code class="filename">query.c</code>.
1920             Log messages of this level will particularly
1921             help identify the cause of SERVFAIL for an
1922             authoritative server.
1923           </p>
1924 <p>
1925             At the debug levels of 2 or higher, detailed context
1926             information of recursive resolutions that resulted in
1927             SERVFAIL is logged.
1928             The log message will look like as follows:
1929           </p>
1930 <p>
1931
1932             </p>
1933 <pre class="programlisting">
1934 fetch completed at resolver.c:2970 for www.example.com/A
1935 in 30.000183: timed out/success [domain:example.com,
1936 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1937 badresp:1,adberr:0,findfail:0,valfail:0]
1938             </pre>
1939 <p>
1940           </p>
1941 <p>
1942             The first part before the colon shows that a recursive
1943             resolution for AAAA records of www.example.com completed
1944             in 30.000183 seconds and the final result that led to the
1945             SERVFAIL was determined at line 2970 of source file
1946             <code class="filename">resolver.c</code>.
1947           </p>
1948 <p>
1949             The following part shows the detected final result and the
1950             latest result of DNSSEC validation.
1951             The latter is always success when no validation attempt
1952             is made.
1953             In this example, this query resulted in SERVFAIL probably
1954             because all name servers are down or unreachable, leading
1955             to a timeout in 30 seconds.
1956             DNSSEC validation was probably not attempted.
1957           </p>
1958 <p>
1959             The last part enclosed in square brackets shows statistics
1960             information collected for this particular resolution
1961             attempt.
1962             The <code class="varname">domain</code> field shows the deepest zone
1963             that the resolver reached;
1964             it is the zone where the error was finally detected.
1965             The meaning of the other fields is summarized in the
1966             following table.
1967           </p>
1968 <div class="informaltable"><table border="1">
1969 <colgroup>
1970 <col>
1971 <col>
1972 </colgroup>
1973 <tbody>
1974 <tr>
1975 <td>
1976                     <p><code class="varname">referral</code></p>
1977                   </td>
1978 <td>
1979                     <p>
1980                       The number of referrals the resolver received
1981                       throughout the resolution process.
1982                       In the above example this is 2, which are most
1983                       likely com and example.com.
1984                     </p>
1985                   </td>
1986 </tr>
1987 <tr>
1988 <td>
1989                     <p><code class="varname">restart</code></p>
1990                   </td>
1991 <td>
1992                     <p>
1993                       The number of cycles that the resolver tried
1994                       remote servers at the <code class="varname">domain</code>
1995                       zone.
1996                       In each cycle the resolver sends one query
1997                       (possibly resending it, depending on the response)
1998                       to each known name server of
1999                       the <code class="varname">domain</code> zone.
2000                     </p>
2001                   </td>
2002 </tr>
2003 <tr>
2004 <td>
2005                     <p><code class="varname">qrysent</code></p>
2006                   </td>
2007 <td>
2008                     <p>
2009                       The number of queries the resolver sent at the
2010                       <code class="varname">domain</code> zone.
2011                     </p>
2012                   </td>
2013 </tr>
2014 <tr>
2015 <td>
2016                     <p><code class="varname">timeout</code></p>
2017                   </td>
2018 <td>
2019                     <p>
2020                       The number of timeouts since the resolver
2021                       received the last response.
2022                     </p>
2023                   </td>
2024 </tr>
2025 <tr>
2026 <td>
2027                     <p><code class="varname">lame</code></p>
2028                   </td>
2029 <td>
2030                     <p>
2031                       The number of lame servers the resolver detected
2032                       at the <code class="varname">domain</code> zone.
2033                       A server is detected to be lame either by an
2034                       invalid response or as a result of lookup in
2035                       BIND9's address database (ADB), where lame
2036                       servers are cached.
2037                     </p>
2038                   </td>
2039 </tr>
2040 <tr>
2041 <td>
2042                     <p><code class="varname">neterr</code></p>
2043                   </td>
2044 <td>
2045                     <p>
2046                       The number of erroneous results that the
2047                       resolver encountered in sending queries
2048                       at the <code class="varname">domain</code> zone.
2049                       One common case is the remote server is
2050                       unreachable and the resolver receives an ICMP
2051                       unreachable error message.
2052                     </p>
2053                   </td>
2054 </tr>
2055 <tr>
2056 <td>
2057                     <p><code class="varname">badresp</code></p>
2058                   </td>
2059 <td>
2060                     <p>
2061                       The number of unexpected responses (other than
2062                       <code class="varname">lame</code>) to queries sent by the
2063                       resolver at the <code class="varname">domain</code> zone.
2064                     </p>
2065                   </td>
2066 </tr>
2067 <tr>
2068 <td>
2069                     <p><code class="varname">adberr</code></p>
2070                   </td>
2071 <td>
2072                     <p>
2073                       Failures in finding remote server addresses
2074                       of the <code class="varname">domain</code> zone in the ADB.
2075                       One common case of this is that the remote
2076                       server's name does not have any address records.
2077                     </p>
2078                   </td>
2079 </tr>
2080 <tr>
2081 <td>
2082                     <p><code class="varname">findfail</code></p>
2083                   </td>
2084 <td>
2085                     <p>
2086                       Failures of resolving remote server addresses.
2087                       This is a total number of failures throughout
2088                       the resolution process.
2089                     </p>
2090                   </td>
2091 </tr>
2092 <tr>
2093 <td>
2094                     <p><code class="varname">valfail</code></p>
2095                   </td>
2096 <td>
2097                     <p>
2098                       Failures of DNSSEC validation.
2099                       Validation failures are counted throughout
2100                       the resolution process (not limited to
2101                       the <code class="varname">domain</code> zone), but should
2102                       only happen in <code class="varname">domain</code>.
2103                     </p>
2104                   </td>
2105 </tr>
2106 </tbody>
2107 </table></div>
2108 <p>
2109             At the debug levels of 3 or higher, the same messages
2110             as those at the debug 1 level are logged for other errors
2111             than SERVFAIL.
2112             Note that negative responses such as NXDOMAIN are not
2113             regarded as errors here.
2114           </p>
2115 <p>
2116             At the debug levels of 4 or higher, the same messages
2117             as those at the debug 2 level are logged for other errors
2118             than SERVFAIL.
2119             Unlike the above case of level 3, messages are logged for
2120             negative responses.
2121             This is because any unexpected results can be difficult to
2122             debug in the recursion case.
2123           </p>
2124 </div>
2125 </div>
2126 <div class="sect2" lang="en">
2127 <div class="titlepage"><div><div><h3 class="title">
2128 <a name="id2577252"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
2129 <p>
2130            This is the grammar of the <span><strong class="command">lwres</strong></span>
2131           statement in the <code class="filename">named.conf</code> file:
2132         </p>
2133 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
2134     [<span class="optional"> listen-on { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ;
2135     [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
2136     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
2137     [<span class="optional"> search { <em class="replaceable"><code>domain_name</code></em> ; [<span class="optional"> <em class="replaceable"><code>domain_name</code></em> ; ... </span>] }; </span>]
2138     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
2139 };
2140 </pre>
2141 </div>
2142 <div class="sect2" lang="en">
2143 <div class="titlepage"><div><div><h3 class="title">
2144 <a name="id2577336"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2145 <p>
2146           The <span><strong class="command">lwres</strong></span> statement configures the
2147           name
2148           server to also act as a lightweight resolver server. (See
2149           <a href="Bv9ARM.ch05.html#lwresd" title="Running a Resolver Daemon">the section called &#8220;Running a Resolver Daemon&#8221;</a>.)  There may be multiple
2150           <span><strong class="command">lwres</strong></span> statements configuring
2151           lightweight resolver servers with different properties.
2152         </p>
2153 <p>
2154           The <span><strong class="command">listen-on</strong></span> statement specifies a
2155           list of
2156           IPv4 addresses (and ports) that this instance of a lightweight
2157           resolver daemon
2158           should accept requests on.  If no port is specified, port 921 is
2159           used.
2160           If this statement is omitted, requests will be accepted on
2161           127.0.0.1,
2162           port 921.
2163         </p>
2164 <p>
2165           The <span><strong class="command">view</strong></span> statement binds this
2166           instance of a
2167           lightweight resolver daemon to a view in the DNS namespace, so that
2168           the
2169           response will be constructed in the same manner as a normal DNS
2170           query
2171           matching this view.  If this statement is omitted, the default view
2172           is
2173           used, and if there is no default view, an error is triggered.
2174         </p>
2175 <p>
2176           The <span><strong class="command">search</strong></span> statement is equivalent to
2177           the
2178           <span><strong class="command">search</strong></span> statement in
2179           <code class="filename">/etc/resolv.conf</code>.  It provides a
2180           list of domains
2181           which are appended to relative names in queries.
2182         </p>
2183 <p>
2184           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2185           the
2186           <span><strong class="command">ndots</strong></span> statement in
2187           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2188           minimum
2189           number of dots in a relative domain name that should result in an
2190           exact match lookup before search path elements are appended.
2191         </p>
2192 </div>
2193 <div class="sect2" lang="en">
2194 <div class="titlepage"><div><div><h3 class="title">
2195 <a name="id2577400"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2196 <pre class="programlisting">
2197 <span><strong class="command">masters</strong></span> <em class="replaceable"><code>name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> |
2198       <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] };
2199 </pre>
2200 </div>
2201 <div class="sect2" lang="en">
2202 <div class="titlepage"><div><div><h3 class="title">
2203 <a name="id2577517"></a><span><strong class="command">masters</strong></span> Statement Definition and
2204           Usage</h3></div></div></div>
2205 <p><span><strong class="command">masters</strong></span>
2206           lists allow for a common set of masters to be easily used by
2207           multiple stub and slave zones in their <span><strong class="command">masters</strong></span>
2208           or <span><strong class="command">also-notify</strong></span> lists.
2209         </p>
2210 </div>
2211 <div class="sect2" lang="en">
2212 <div class="titlepage"><div><div><h3 class="title">
2213 <a name="id2577539"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2214 <p>
2215           This is the grammar of the <span><strong class="command">options</strong></span>
2216           statement in the <code class="filename">named.conf</code> file:
2217         </p>
2218 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2219     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2220     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2221     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2222     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2223     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2224     [<span class="optional"> geoip-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2225     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2226     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2227     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2228     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2229     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2230     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2231     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2232     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2233     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2234     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2235     [<span class="optional"> secroots-file <em class="replaceable"><code>path_name</code></em>; </span>]
2236     [<span class="optional"> session-keyfile <em class="replaceable"><code>path_name</code></em>; </span>]
2237     [<span class="optional"> session-keyname <em class="replaceable"><code>key_name</code></em>; </span>]
2238     [<span class="optional"> session-keyalg <em class="replaceable"><code>algorithm_id</code></em>; </span>]
2239     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2240     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2241     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2242     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2243     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2244     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
2245     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2246     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2247     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2248     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2249     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2250     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2251     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2252     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2253     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2254     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2255     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2256     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em>; </span>]
2257     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2258     [<span class="optional"> request-sit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2259     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2260     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2261     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2262     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2263     [<span class="optional"> ixfr-from-differences (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">master</code> | <code class="constant">slave</code>); </span>]
2264     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2265     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2266     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2267                         <em class="replaceable"><code>no</code></em> |
2268                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2269     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2270     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2271     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2272     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
2273     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] {
2274         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] |
2275           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>]) ;
2276         ... }; </span>]
2277     [<span class="optional"> check-names ( <em class="replaceable"><code>master</code></em> | <em class="replaceable"><code>slave</code></em> | <em class="replaceable"><code>response</code></em> )
2278         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2279     [<span class="optional"> check-dup-records ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2280     [<span class="optional"> check-mx ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2281     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2282     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2283     [<span class="optional"> check-mx-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2284     [<span class="optional"> check-srv-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2285     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2286     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2287     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2288     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2289     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2290     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2291     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2292     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2293     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2294     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2295     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2296     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2297     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2298     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2299     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
2300     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2301     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
2302     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2303     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2304     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2305     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2306     [<span class="optional"> no-case-compress { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2307     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2308     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2309     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2310     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2311     [<span class="optional"> listen-on [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em> </span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2312     [<span class="optional"> listen-on-v6 [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>]
2313 { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2314     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2315         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2316         [<span class="optional"> dscp <em class="replaceable"><code>ip_dscp</code></em></span>] |
2317         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2318         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] )
2319         [<span class="optional"> dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2320     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2321         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2322         [<span class="optional"> dscp <em class="replaceable"><code>ip_dscp</code></em></span>] |
2323         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2324         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] )
2325         [<span class="optional"> dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2326     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2327     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2328     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2329     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2330     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2331     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2332     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2333     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2334     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2335     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2336     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2337     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2338     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2339     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2340     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2341     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2342     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2343     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2344     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2345     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2346     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2347     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2348     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2349     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2350     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
2351     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2352     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em>
2353                     [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] [<span class="optional">key <em class="replaceable"><code>keyname</code></em></span>] ;
2354                     [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] [<span class="optional">key <em class="replaceable"><code>keyname</code></em></span>] ; ... </span>] }; </span>]
2355     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2356     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2357     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2358     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2359     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2360     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2361     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2362     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2363     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2364     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2365     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2366     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2367     [<span class="optional"> rrset-order { <em class="replaceable"><code>order_spec</code></em> ; [<span class="optional"> <em class="replaceable"><code>order_spec</code></em> ; ... </span>] </span>] };
2368     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2369     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2370     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2371     [<span class="optional"> max-zone-ttl <em class="replaceable"><code>number</code></em> ; </span>]
2372     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
2373     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2374     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2375     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2376     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2377     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2378     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2379     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2380     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2381     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2382     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2383     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2384     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2385     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2386     [<span class="optional"> dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ;
2387     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2388     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2389     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2390     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2391     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2392     [<span class="optional"> filter-aaaa-on-v4 ( <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>break-dnssec</code></em> ); </span>]
2393     [<span class="optional"> filter-aaaa-on-v6 ( <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>break-dnssec</code></em> ); </span>]
2394     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2395     [<span class="optional"> dns64 <em class="replaceable"><code>ipv6-prefix</code></em> {
2396         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2397         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2398         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2399         [<span class="optional"> suffix IPv6-address; </span>]
2400         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2401         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2402     }; </span>];
2403     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2404     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2405     [<span class="optional"> preferred-glue ( <em class="replaceable"><code>A</code></em> | <em class="replaceable"><code>AAAA</code></em> | <em class="replaceable"><code>NONE</code></em> ); </span>]
2406     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2407     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2408     [<span class="optional"> max-rsa-exponent-size <em class="replaceable"><code>number</code></em>; </span>]
2409     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2410     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2411     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2412                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2413     [<span class="optional"> disable-ds-digests <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>digest_type</code></em>;
2414                                 [<span class="optional"> <em class="replaceable"><code>digest_type</code></em>; </span>] }; </span>]
2415     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2416     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2417     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2418     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2419     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2420     [<span class="optional"> max-recursion-depth <em class="replaceable"><code>number</code></em> ; </span>]
2421     [<span class="optional"> max-recursion-queries <em class="replaceable"><code>number</code></em> ; </span>]
2422     [<span class="optional"> masterfile-format
2423             (<code class="constant">text</code>|<code class="constant">raw</code>|<code class="constant">map</code>) ; </span>]
2424     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2425     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2426     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2427     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2428     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2429     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2430     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2431     [<span class="optional"> deny-answer-addresses { <em class="replaceable"><code>address_match_list</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2432     [<span class="optional"> deny-answer-aliases { <em class="replaceable"><code>namelist</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2433     [<span class="optional"> prefetch <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
2434
2435     [<span class="optional"> rate-limit {
2436         [<span class="optional"> responses-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2437         [<span class="optional"> referrals-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2438         [<span class="optional"> nodata-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2439         [<span class="optional"> nxdomains-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2440         [<span class="optional"> errors-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2441         [<span class="optional"> all-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2442         [<span class="optional"> window <em class="replaceable"><code>number</code></em> ; </span>]
2443         [<span class="optional"> log-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2444         [<span class="optional"> qps-scale <em class="replaceable"><code>number</code></em> ; </span>]
2445         [<span class="optional"> ipv4-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2446         [<span class="optional"> ipv6-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2447         [<span class="optional"> slip <em class="replaceable"><code>number</code></em> ; </span>]
2448         [<span class="optional"> exempt-clients  { <em class="replaceable"><code>address_match_list</code></em> } ; </span>]
2449         [<span class="optional"> max-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2450         [<span class="optional"> min-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2451     } ; </span>]
2452     [<span class="optional"> response-policy {
2453         zone <em class="replaceable"><code>zone_name</code></em>
2454         [<span class="optional"> policy <em class="replaceable"><code>(given | disabled | passthru | drop |
2455                   nxdomain | nodata | cname domain</code></em>) </span>]
2456         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>]
2457         [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>]
2458         ; [<span class="optional">...</span>]
2459     } [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>]
2460       [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>]
2461       [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em> </span>]
2462       [<span class="optional"> min-ns-dots <em class="replaceable"><code>number</code></em> </span>]
2463       [<span class="optional"> qname-wait-recurse <em class="replaceable"><code>yes_or_no</code></em> </span>]
2464     ; </span>]
2465 };
2466 </pre>
2467 </div>
2468 <div class="sect2" lang="en">
2469 <div class="titlepage"><div><div><h3 class="title">
2470 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2471           Usage</h3></div></div></div>
2472 <p>
2473           The <span><strong class="command">options</strong></span> statement sets up global
2474           options
2475           to be used by <acronym class="acronym">BIND</acronym>. This statement
2476           may appear only
2477           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2478           statement, an options block with each option set to its default will
2479           be used.
2480         </p>
2481 <div class="variablelist"><dl>
2482 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2483 <dd>
2484 <p>
2485                   Allows multiple views to share a single cache
2486                   database.
2487                   Each view has its own cache database by default, but
2488                   if multiple views have the same operational policy
2489                   for name resolution and caching, those views can
2490                   share a single cache to save memory and possibly
2491                   improve resolution efficiency by using this option.
2492                 </p>
2493 <p>
2494                   The <span><strong class="command">attach-cache</strong></span> option
2495                   may also be specified in <span><strong class="command">view</strong></span>
2496                   statements, in which case it overrides the
2497                   global <span><strong class="command">attach-cache</strong></span> option.
2498                 </p>
2499 <p>
2500                   The <em class="replaceable"><code>cache_name</code></em> specifies
2501                   the cache to be shared.
2502                   When the <span><strong class="command">named</strong></span> server configures
2503                   views which are supposed to share a cache, it
2504                   creates a cache with the specified name for the
2505                   first view of these sharing views.
2506                   The rest of the views will simply refer to the
2507                   already created cache.
2508                 </p>
2509 <p>
2510                   One common configuration to share a cache would be to
2511                   allow all views to share a single cache.
2512                   This can be done by specifying
2513                   the <span><strong class="command">attach-cache</strong></span> as a global
2514                   option with an arbitrary name.
2515                 </p>
2516 <p>
2517                   Another possible operation is to allow a subset of
2518                   all views to share a cache while the others to
2519                   retain their own caches.
2520                   For example, if there are three views A, B, and C,
2521                   and only A and B should share a cache, specify the
2522                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2523                   B)'s option, referring to the other view name:
2524                 </p>
2525 <pre class="programlisting">
2526   view "A" {
2527     // this view has its own cache
2528     ...
2529   };
2530   view "B" {
2531     // this view refers to A's cache
2532     attach-cache "A";
2533   };
2534   view "C" {
2535     // this view has its own cache
2536     ...
2537   };
2538 </pre>
2539 <p>
2540                   Views that share a cache must have the same policy
2541                   on configurable parameters that may affect caching.
2542                   The current implementation requires the following
2543                   configurable options be consistent among these
2544                   views:
2545                   <span><strong class="command">check-names</strong></span>,
2546                   <span><strong class="command">cleaning-interval</strong></span>,
2547                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2548                   <span><strong class="command">dnssec-validation</strong></span>,
2549                   <span><strong class="command">max-cache-ttl</strong></span>,
2550                   <span><strong class="command">max-ncache-ttl</strong></span>,
2551                   <span><strong class="command">max-cache-size</strong></span>, and
2552                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2553                 </p>
2554 <p>
2555                   Note that there may be other parameters that may
2556                   cause confusion if they are inconsistent for
2557                   different views that share a single cache.
2558                   For example, if these views define different sets of
2559                   forwarders that can return different answers for the
2560                   same question, sharing the answer does not make
2561                   sense or could even be harmful.
2562                   It is administrator's responsibility to ensure
2563                   configuration differences in different views do
2564                   not cause disruption with a shared cache.
2565                 </p>
2566 </dd>
2567 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2568 <dd><p>
2569                 The working directory of the server.
2570                 Any non-absolute pathnames in the configuration file will be
2571                 taken
2572                 as relative to this directory. The default location for most
2573                 server
2574                 output files (e.g. <code class="filename">named.run</code>)
2575                 is this directory.
2576                 If a directory is not specified, the working directory
2577                 defaults to `<code class="filename">.</code>', the directory from
2578                 which the server
2579                 was started. The directory specified should be an absolute
2580                 path.
2581               </p></dd>
2582 <dt><span class="term"><span><strong class="command">geoip-directory</strong></span></span></dt>
2583 <dd><p>
2584                 Specifies the directory containing GeoIP
2585                 <code class="filename">.dat</code> database files for GeoIP
2586                 initialization.  By default, this option is unset
2587                 and the GeoIP support will use libGeoIP's
2588                 built-in directory.
2589                 (For details, see <a href="Bv9ARM.ch06.html#acl" title="acl Statement Definition and
2590           Usage">the section called &#8220;<span><strong class="command">acl</strong></span> Statement Definition and
2591           Usage&#8221;</a> about the
2592                 <span><strong class="command">geoip</strong></span> ACL.)
2593               </p></dd>
2594 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2595 <dd><p>
2596                 When performing dynamic update of secure zones, the
2597                 directory where the public and private DNSSEC key files
2598                 should be found, if different than the current working
2599                 directory.  (Note that this option has no effect on the
2600                 paths for files containing non-DNSSEC keys such as
2601                 <code class="filename">bind.keys</code>,
2602                 <code class="filename">rndc.key</code> or
2603                 <code class="filename">session.key</code>.)
2604               </p></dd>
2605 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2606 <dd>
2607 <p>
2608                 Specifies the directory in which to store the files that
2609                 track managed DNSSEC keys.  By default, this is the working
2610                 directory.
2611               </p>
2612 <p>
2613                 If <span><strong class="command">named</strong></span> is not configured to use views,
2614                 then managed keys for the server will be tracked in a single
2615                 file called <code class="filename">managed-keys.bind</code>.
2616                 Otherwise, managed keys will be tracked in separate files,
2617                 one file per view; each file name will be the SHA256 hash
2618                 of the view name, followed by the extension
2619                 <code class="filename">.mkeys</code>.
2620               </p>
2621 </dd>
2622 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2623 <dd><p>
2624                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2625                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2626                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2627                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2628                 <span><strong class="command">named-xfer</strong></span> program is needed;
2629                 its functionality is built into the name server.
2630               </p></dd>
2631 <dt><span class="term"><span><strong class="command">tkey-gssapi-keytab</strong></span></span></dt>
2632 <dd><p>
2633                 The KRB5 keytab file to use for GSS-TSIG updates. If
2634                 this option is set and tkey-gssapi-credential is not
2635                 set, then updates will be allowed with any key
2636                 matching a principal in the specified keytab.
2637               </p></dd>
2638 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2639 <dd><p>
2640                 The security credential with which the server should
2641                 authenticate keys requested by the GSS-TSIG protocol.
2642                 Currently only Kerberos 5 authentication is available
2643                 and the credential is a Kerberos principal which the
2644                 server can acquire through the default system key
2645                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2646                 The location keytab file can be overridden using the
2647                 tkey-gssapi-keytab option. Normally this principal is
2648                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2649                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span> must
2650                 also be set if a specific keytab is not set with
2651                 tkey-gssapi-keytab.
2652               </p></dd>
2653 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2654 <dd><p>
2655                 The domain appended to the names of all shared keys
2656                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2657                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2658                 it may or may not specify the desired name for the
2659                 key. If present, the name of the shared key will
2660                 be <code class="varname">client specified part</code> +
2661                 <code class="varname">tkey-domain</code>.  Otherwise, the
2662                 name of the shared key will be <code class="varname">random hex
2663                 digits</code> + <code class="varname">tkey-domain</code>.
2664                 In most cases, the <span><strong class="command">domainname</strong></span>
2665                 should be the server's domain name, or an otherwise
2666                 non-existent subdomain like
2667                 "_tkey.<code class="varname">domainname</code>".  If you are
2668                 using GSS-TSIG, this variable must be defined, unless
2669                 you specify a specific keytab using tkey-gssapi-keytab.
2670               </p></dd>
2671 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2672 <dd><p>
2673                 The Diffie-Hellman key used by the server
2674                 to generate shared keys with clients using the Diffie-Hellman
2675                 mode
2676                 of <span><strong class="command">TKEY</strong></span>. The server must be
2677                 able to load the
2678                 public and private keys from files in the working directory.
2679                 In
2680                 most cases, the keyname should be the server's host name.
2681               </p></dd>
2682 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2683 <dd><p>
2684                 This is for testing only.  Do not use.
2685               </p></dd>
2686 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2687 <dd><p>
2688                 The pathname of the file the server dumps
2689                 the database to when instructed to do so with
2690                 <span><strong class="command">rndc dumpdb</strong></span>.
2691                 If not specified, the default is <code class="filename">named_dump.db</code>.
2692               </p></dd>
2693 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2694 <dd><p>
2695                 The pathname of the file the server writes memory
2696                 usage statistics to on exit. If not specified,
2697                 the default is <code class="filename">named.memstats</code>.
2698               </p></dd>
2699 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2700 <dd><p>
2701                 The pathname of the file the server writes its process ID
2702                 in. If not specified, the default is
2703                 <code class="filename">/var/run/named/named.pid</code>.
2704                 The PID file is used by programs that want to send signals to
2705                 the running
2706                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2707                 use of a PID file &#8212; no file will be written and any
2708                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2709                 is a keyword, not a filename, and therefore is not enclosed
2710                 in
2711                 double quotes.
2712               </p></dd>
2713 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2714 <dd><p>
2715                 The pathname of the file the server dumps
2716                 the queries that are currently recursing when instructed
2717                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2718                 If not specified, the default is <code class="filename">named.recursing</code>.
2719               </p></dd>
2720 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2721 <dd><p>
2722                 The pathname of the file the server appends statistics
2723                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2724                 If not specified, the default is <code class="filename">named.stats</code> in the
2725                 server's current directory.  The format of the file is
2726                 described
2727                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2728               </p></dd>
2729 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2730 <dd><p>
2731                 The pathname of a file to override the built-in trusted
2732                 keys provided by <span><strong class="command">named</strong></span>.
2733                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2734                 and <span><strong class="command">dnssec-validation</strong></span> for details.
2735                 If not specified, the default is
2736                 <code class="filename">/etc/bind.keys</code>.
2737               </p></dd>
2738 <dt><span class="term"><span><strong class="command">secroots-file</strong></span></span></dt>
2739 <dd><p>
2740                 The pathname of the file the server dumps
2741                 security roots to when instructed to do so with
2742                 <span><strong class="command">rndc secroots</strong></span>.
2743                 If not specified, the default is
2744                 <code class="filename">named.secroots</code>.
2745               </p></dd>
2746 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2747 <dd><p>
2748                 The pathname of the file into which to write a TSIG
2749                 session key generated by <span><strong class="command">named</strong></span> for use by
2750                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2751                 default is <code class="filename">/var/run/named/session.key</code>.
2752                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2753                 particular the discussion of the
2754                 <span><strong class="command">update-policy</strong></span> statement's
2755                 <strong class="userinput"><code>local</code></strong> option for more
2756                 information about this feature.)
2757               </p></dd>
2758 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2759 <dd><p>
2760                 The key name to use for the TSIG session key.
2761                 If not specified, the default is "local-ddns".
2762               </p></dd>
2763 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2764 <dd><p>
2765                 The algorithm to use for the TSIG session key.
2766                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2767                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2768                 specified, the default is hmac-sha256.
2769               </p></dd>
2770 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2771 <dd><p>
2772                 The UDP/TCP port number the server uses for
2773                 receiving and sending DNS protocol traffic.
2774                 The default is 53.  This option is mainly intended for server
2775                 testing;
2776                 a server using a port other than 53 will not be able to
2777                 communicate with
2778                 the global DNS.
2779               </p></dd>
2780 <dt><span class="term"><span><strong class="command">dscp</strong></span></span></dt>
2781 <dd><p>
2782                 The global Differentiated Services Code Point (DSCP)
2783                 value to classify outgoing DNS traffic on operating
2784                 systems that support DSCP. Valid values are 0 through 63.
2785                 It is not configured by default.
2786               </p></dd>
2787 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2788 <dd><p>
2789                 The source of entropy to be used by the server.  Entropy is
2790                 primarily needed
2791                 for DNSSEC operations, such as TKEY transactions and dynamic
2792                 update of signed
2793                 zones.  This options specifies the device (or file) from which
2794                 to read
2795                 entropy.  If this is a file, operations requiring entropy will
2796                 fail when the
2797                 file has been exhausted.  If not specified, the default value
2798                 is
2799                 <code class="filename">/dev/random</code>
2800                 (or equivalent) when present, and none otherwise.  The
2801                 <span><strong class="command">random-device</strong></span> option takes
2802                 effect during
2803                 the initial configuration load at server startup time and
2804                 is ignored on subsequent reloads.
2805               </p></dd>
2806 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2807 <dd><p>
2808                 If specified, the listed type (A or AAAA) will be emitted
2809                 before other glue
2810                 in the additional section of a query response.
2811                 The default is not to prefer any type (NONE).
2812               </p></dd>
2813 <dt>
2814 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2815 </dt>
2816 <dd>
2817 <p>
2818                 Turn on enforcement of delegation-only in TLDs
2819                 (top level domains) and root zones with an optional
2820                 exclude list.
2821               </p>
2822 <p>
2823                 DS queries are expected to be made to and be answered by
2824                 delegation only zones.  Such queries and responses are
2825                 treated as an exception to delegation-only processing
2826                 and are not converted to NXDOMAIN responses provided
2827                 a CNAME is not discovered at the query name.
2828               </p>
2829 <p>
2830                 If a delegation only zone server also serves a child
2831                 zone it is not always possible to determine whether
2832                 an answer comes from the delegation only zone or the
2833                 child zone.  SOA NS and DNSKEY records are apex
2834                 only records and a matching response that contains
2835                 these records or DS is treated as coming from a
2836                 child zone.  RRSIG records are also examined to see
2837                 if they are signed by a child zone or not.  The
2838                 authority section is also examined to see if there
2839                 is evidence that the answer is from the child zone.
2840                 Answers that are determined to be from a child zone
2841                 are not converted to NXDOMAIN responses.  Despite
2842                 all these checks there is still a possibility of
2843                 false negatives when a child zone is being served.
2844               </p>
2845 <p>
2846                 Similarly false positives can arise from empty nodes
2847                 (no records at the name) in the delegation only zone
2848                 when the query type is not ANY.
2849               </p>
2850 <p>
2851                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2852                 "US" and "MUSEUM").  This list is not exhaustive.
2853               </p>
2854 <pre class="programlisting">
2855 options {
2856         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2857 };
2858 </pre>
2859 </dd>
2860 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2861 <dd>
2862 <p>
2863                 Disable the specified DNSSEC algorithms at and below the
2864                 specified name.
2865                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2866                 statements are allowed.
2867                 Only the best match <span><strong class="command">disable-algorithms</strong></span>
2868                 clause will be used to determine which algorithms are used.
2869               </p>
2870 <p>
2871                 If all supported algorithms are disabled, the zones covered
2872                 by the <span><strong class="command">disable-algorithms</strong></span> will be treated
2873                 as insecure.
2874               </p>
2875 </dd>
2876 <dt><span class="term"><span><strong class="command">disable-ds-digests</strong></span></span></dt>
2877 <dd>
2878 <p>
2879                 Disable the specified DS/DLV digest types at and below the
2880                 specified name.
2881                 Multiple <span><strong class="command">disable-ds-digests</strong></span>
2882                 statements are allowed.
2883                 Only the best match <span><strong class="command">disable-ds-digests</strong></span>
2884                 clause will be used to determine which digest types are used.
2885               </p>
2886 <p>
2887                 If all supported digest types are disabled, the zones covered
2888                 by the <span><strong class="command">disable-ds-digests</strong></span> will be treated
2889                 as insecure.
2890               </p>
2891 </dd>
2892 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2893 <dd>
2894 <p>
2895                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2896                 validator with an alternate method to validate DNSKEY
2897                 records at the top of a zone.  When a DNSKEY is at or
2898                 below a domain specified by the deepest
2899                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2900                 validation has left the key untrusted, the trust-anchor
2901                 will be appended to the key name and a DLV record will be
2902                 looked up to see if it can validate the key.  If the DLV
2903                 record validates a DNSKEY (similarly to the way a DS
2904                 record does) the DNSKEY RRset is deemed to be trusted.
2905               </p>
2906 <p>
2907                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2908                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2909                 values for the DLV domain and trust anchor will be
2910                 used, along with a built-in key for validation.
2911               </p>
2912 <p>
2913                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2914                 <strong class="userinput"><code>no</code></strong>, then dnssec-lookaside
2915                 is not used.
2916               </p>
2917 <p>
2918                 The default DLV key is stored in the file
2919                 <code class="filename">bind.keys</code>;
2920                 <span><strong class="command">named</strong></span> will load that key at
2921                 startup if <span><strong class="command">dnssec-lookaside</strong></span> is set to
2922                 <code class="constant">auto</code>.  A copy of the file is
2923                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2924                 current as of the release date.  If the DLV key expires, a
2925                 new copy of <code class="filename">bind.keys</code> can be downloaded
2926                 from <a href="https://www.isc.org/solutions/dlv/" target="_top">https://www.isc.org/solutions/dlv/</a>.
2927               </p>
2928 <p>
2929                 (To prevent problems if <code class="filename">bind.keys</code> is
2930                 not found, the current key is also compiled in to
2931                 <span><strong class="command">named</strong></span>.  Relying on this is not
2932                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2933                 to be recompiled with a new key when the DLV key expires.)
2934               </p>
2935 <p>
2936                 NOTE: <span><strong class="command">named</strong></span> only loads certain specific
2937                 keys from <code class="filename">bind.keys</code>:  those for the
2938                 DLV zone and for the DNS root zone.  The file cannot be
2939                 used to store keys for other zones.
2940               </p>
2941 </dd>
2942 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2943 <dd><p>
2944                 Specify hierarchies which must be or may not be secure
2945                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2946                 then <span><strong class="command">named</strong></span> will only accept answers if
2947                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2948                 DNSSEC validation applies allowing for insecure answers to
2949                 be accepted.  The specified domain must be under a
2950                 <span><strong class="command">trusted-keys</strong></span> or
2951                 <span><strong class="command">managed-keys</strong></span> statement, or
2952                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2953               </p></dd>
2954 <dt><span class="term"><span><strong class="command">dns64</strong></span></span></dt>
2955 <dd>
2956 <p>
2957                 This directive instructs <span><strong class="command">named</strong></span> to
2958                 return mapped IPv4 addresses to AAAA queries when
2959                 there are no AAAA records.  It is intended to be
2960                 used in conjunction with a NAT64.  Each
2961                 <span><strong class="command">dns64</strong></span> defines one DNS64 prefix.
2962                 Multiple DNS64 prefixes can be defined.
2963               </p>
2964 <p>
2965                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2966                 64 and 96 as per RFC 6052.
2967               </p>
2968 <p>
2969                 Additionally a reverse IP6.ARPA zone will be created for
2970                 the prefix to provide a mapping from the IP6.ARPA names
2971                 to the corresponding IN-ADDR.ARPA names using synthesized
2972                 CNAMEs.  <span><strong class="command">dns64-server</strong></span> and
2973                 <span><strong class="command">dns64-contact</strong></span> can be used to specify
2974                 the name of the server and contact for the zones. These
2975                 are settable at the view / options level.  These are
2976                 not settable on a per-prefix basis.
2977               </p>
2978 <p>
2979                 Each <span><strong class="command">dns64</strong></span> supports an optional
2980                 <span><strong class="command">clients</strong></span> ACL that determines which
2981                 clients are affected by this directive.  If not defined,
2982                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2983               </p>
2984 <p>
2985                 Each <span><strong class="command">dns64</strong></span> supports an optional
2986                 <span><strong class="command">mapped</strong></span> ACL that selects which
2987                 IPv4 addresses are to be mapped in the corresponding
2988                 A RRset.  If not defined it defaults to
2989                 <strong class="userinput"><code>any;</code></strong>.
2990               </p>
2991 <p>
2992                 Normally, DNS64 won't apply to a domain name that
2993                 owns one or more AAAA records; these records will
2994                 simply be returned.  The optional
2995                 <span><strong class="command">exclude</strong></span> ACL allows specification
2996                 of a list of IPv6 addresses that will be ignored
2997                 if they appear in a domain name's AAAA records, and
2998                 DNS64 will be applied to any A records the domain
2999                 name owns.  If not defined, <span><strong class="command">exclude</strong></span>
3000                 defaults to none.
3001               </p>
3002 <p>
3003                 A optional <span><strong class="command">suffix</strong></span> can also
3004                 be defined to set the bits trailing the mapped
3005                 IPv4 address bits.  By default these bits are
3006                 set to <strong class="userinput"><code>::</code></strong>.  The bits
3007                 matching the prefix and mapped IPv4 address
3008                 must be zero.
3009               </p>
3010 <p>
3011                 If <span><strong class="command">recursive-only</strong></span> is set to
3012                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
3013                 only happen for recursive queries.  The default
3014                 is <span><strong class="command">no</strong></span>.
3015               </p>
3016 <p>
3017                 If <span><strong class="command">break-dnssec</strong></span> is set to
3018                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
3019                 happen even if the result, if validated, would
3020                 cause a DNSSEC validation failure.  If this option
3021                 is set to <span><strong class="command">no</strong></span> (the default), the DO
3022                 is set on the incoming query, and there are RRSIGs on
3023                 the applicable records, then synthesis will not happen.
3024               </p>
3025 <pre class="programlisting">
3026         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
3027
3028         dns64 64:FF9B::/96 {
3029                 clients { any; };
3030                 mapped { !rfc1918; any; };
3031                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
3032                 suffix ::;
3033         };
3034 </pre>
3035 </dd>
3036 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
3037 <dd>
3038 <p>
3039                   If this option is set to its default value of
3040                   <code class="literal">maintain</code> in a zone of type
3041                   <code class="literal">master</code> which is DNSSEC-signed
3042                   and configured to allow dynamic updates (see
3043                   <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>), and
3044                   if <span><strong class="command">named</strong></span> has access to the
3045                   private signing key(s) for the zone, then
3046                   <span><strong class="command">named</strong></span> will automatically sign all new
3047                   or changed records and maintain signatures for the zone
3048                   by regenerating RRSIG records whenever they approach
3049                   their expiration date.
3050                 </p>
3051 <p>
3052                   If the option is changed to <code class="literal">no-resign</code>,
3053                   then <span><strong class="command">named</strong></span> will sign all new or
3054                   changed records, but scheduled maintenance of
3055                   signatures is disabled.
3056                 </p>
3057 <p>
3058                   With either of these settings, <span><strong class="command">named</strong></span>
3059                   will reject updates to a DNSSEC-signed zone when the
3060                   signing keys are inactive or unavailable to
3061                   <span><strong class="command">named</strong></span>.  (A planned third option,
3062                   <code class="literal">external</code>, will disable all automatic
3063                   signing and allow DNSSEC data to be submitted into a zone
3064                   via dynamic update; this is not yet implemented.)
3065                 </p>
3066 </dd>
3067 <dt><span class="term"><span><strong class="command">max-zone-ttl</strong></span></span></dt>
3068 <dd>
3069 <p>
3070                 Specifies a maximum permissible TTL value.
3071                 When loading a zone file using a
3072                 <code class="option">masterfile-format</code> of
3073                 <code class="constant">text</code> or <code class="constant">raw</code>,
3074                 any record encountered with a TTL higher than
3075                 <code class="option">max-zone-ttl</code> will cause the zone to
3076                 be rejected.
3077               </p>
3078 <p>
3079                 This is useful in DNSSEC-signed zones because when
3080                 rolling to a new DNSKEY, the old key needs to remain
3081                 available until RRSIG records have expired from
3082                 caches.  The<code class="option">max-zone-ttl</code> option guarantees
3083                 that the largest TTL in the zone will be no higher
3084                 the set value.
3085               </p>
3086 <p>
3087                 (NOTE: Because <code class="constant">map</code>-format files
3088                 load directly into memory, this option cannot be
3089                 used with them.)
3090               </p>
3091 </dd>
3092 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
3093 <dd>
3094 <p>
3095                 If <strong class="userinput"><code>full</code></strong>, the server will collect
3096                 statistical data on all zones (unless specifically
3097                 turned off on a per-zone basis by specifying
3098                 <span><strong class="command">zone-statistics terse</strong></span> or
3099                 <span><strong class="command">zone-statistics none</strong></span>
3100                 in the <span><strong class="command">zone</strong></span> statement).
3101                 The default is <strong class="userinput"><code>terse</code></strong>, providing
3102                 minimal statistics on zones (including name and
3103                 current serial number, but not query type
3104                 counters).
3105               </p>
3106 <p>
3107                 These statistics may be accessed via the
3108                 <span><strong class="command">statistics-channel</strong></span> or
3109                 using <span><strong class="command">rndc stats</strong></span>, which
3110                 will dump them to the file listed
3111                 in the <span><strong class="command">statistics-file</strong></span>.  See
3112                 also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
3113               </p>
3114 <p>
3115                 For backward compatibility with earlier versions
3116                 of BIND 9, the <span><strong class="command">zone-statistics</strong></span>
3117                 option can also accept <strong class="userinput"><code>yes</code></strong>
3118                 or <strong class="userinput"><code>no</code></strong>; <strong class="userinput"><code>yes</code></strong>
3119                 has the same meaning as <strong class="userinput"><code>full</code></strong>.
3120                 As of <acronym class="acronym">BIND</acronym> 9.10,
3121                 <strong class="userinput"><code>no</code></strong> has the same meaning
3122                 as <strong class="userinput"><code>none</code></strong>; previously, it
3123                 was the same as <strong class="userinput"><code>terse</code></strong>.
3124               </p>
3125 </dd>
3126 </dl></div>
3127 <div class="sect3" lang="en">
3128 <div class="titlepage"><div><div><h4 class="title">
3129 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
3130 <div class="variablelist"><dl>
3131 <dt><span class="term"><span><strong class="command">automatic-interface-scan</strong></span></span></dt>
3132 <dd>
3133 <p>
3134                   If <strong class="userinput"><code>yes</code></strong> and supported by the OS,
3135                   automatically rescan network interfaces when the interface
3136                   addresses are added or removed.  The default is
3137                   <strong class="userinput"><code>yes</code></strong>.
3138                 </p>
3139 <p>
3140                   Currently the OS needs to support routing sockets for
3141                   <span><strong class="command">automatic-interface-scan</strong></span> to be
3142                   supported.
3143                 </p>
3144 </dd>
3145 <dt><span class="term"><span><strong class="command">allow-new-zones</strong></span></span></dt>
3146 <dd><p>
3147                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
3148                   added at runtime via <span><strong class="command">rndc addzone</strong></span>
3149                   or deleted via <span><strong class="command">rndc delzone</strong></span>.
3150                   The default is <strong class="userinput"><code>no</code></strong>.
3151                 </p></dd>
3152 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
3153 <dd><p>
3154                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
3155                   is always set on NXDOMAIN responses, even if the server is
3156                   not actually
3157                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
3158                   this is
3159                   a change from <acronym class="acronym">BIND</acronym> 8. If you
3160                   are using very old DNS software, you
3161                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
3162                 </p></dd>
3163 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
3164 <dd><p>
3165                   This option was used in <acronym class="acronym">BIND</acronym>
3166                   8 to enable checking
3167                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
3168                   the checks.
3169                 </p></dd>
3170 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
3171 <dd><p>
3172                   Write memory statistics to the file specified by
3173                   <span><strong class="command">memstatistics-file</strong></span> at exit.
3174                   The default is <strong class="userinput"><code>no</code></strong> unless
3175                   '-m record' is specified on the command line in
3176                   which case it is <strong class="userinput"><code>yes</code></strong>.
3177                 </p></dd>
3178 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
3179 <dd>
3180 <p>
3181                   If <strong class="userinput"><code>yes</code></strong>, then the
3182                   server treats all zones as if they are doing zone transfers
3183                   across
3184                   a dial-on-demand dialup link, which can be brought up by
3185                   traffic
3186                   originating from this server. This has different effects
3187                   according
3188                   to zone type and concentrates the zone maintenance so that
3189                   it all
3190                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
3191                   hopefully during the one call. It also suppresses some of
3192                   the normal
3193                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
3194                 </p>
3195 <p>
3196                   The <span><strong class="command">dialup</strong></span> option
3197                   may also be specified in the <span><strong class="command">view</strong></span> and
3198                   <span><strong class="command">zone</strong></span> statements,
3199                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
3200                   option.
3201                 </p>
3202 <p>
3203                   If the zone is a master zone, then the server will send out a
3204                   NOTIFY
3205                   request to all the slaves (default). This should trigger the
3206                   zone serial
3207                   number check in the slave (providing it supports NOTIFY)
3208                   allowing the slave
3209                   to verify the zone while the connection is active.
3210                   The set of servers to which NOTIFY is sent can be controlled
3211                   by
3212                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
3213                 </p>
3214 <p>
3215                   If the
3216                   zone is a slave or stub zone, then the server will suppress
3217                   the regular
3218                   "zone up to date" (refresh) queries and only perform them
3219                   when the
3220                   <span><strong class="command">heartbeat-interval</strong></span> expires in
3221                   addition to sending
3222                   NOTIFY requests.
3223                 </p>
3224 <p>
3225                   Finer control can be achieved by using
3226                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
3227                   messages,
3228                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
3229                   messages and
3230                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
3231                   which suppresses normal refresh processing and sends refresh
3232                   queries
3233                   when the <span><strong class="command">heartbeat-interval</strong></span>
3234                   expires, and
3235                   <strong class="userinput"><code>passive</code></strong> which just disables normal
3236                   refresh
3237                   processing.
3238                 </p>
3239 <div class="informaltable"><table border="1">
3240 <colgroup>
3241 <col>
3242 <col>
3243 <col>
3244 <col>
3245 </colgroup>
3246 <tbody>
3247 <tr>
3248 <td>
3249                           <p>
3250                             dialup mode
3251                           </p>
3252                         </td>
3253 <td>
3254                           <p>
3255                             normal refresh
3256                           </p>
3257                         </td>
3258 <td>
3259                           <p>
3260                             heart-beat refresh
3261                           </p>
3262                         </td>
3263 <td>
3264                           <p>
3265                             heart-beat notify
3266                           </p>
3267                         </td>
3268 </tr>
3269 <tr>
3270 <td>
3271                           <p><span><strong class="command">no</strong></span> (default)</p>
3272                         </td>
3273 <td>
3274                           <p>
3275                             yes
3276                           </p>
3277                         </td>
3278 <td>
3279                           <p>
3280                             no
3281                           </p>
3282                         </td>
3283 <td>
3284                           <p>
3285                             no
3286                           </p>
3287                         </td>
3288 </tr>
3289 <tr>
3290 <td>
3291                           <p><span><strong class="command">yes</strong></span></p>
3292                         </td>
3293 <td>
3294                           <p>
3295                             no
3296                           </p>
3297                         </td>
3298 <td>
3299                           <p>
3300                             yes
3301                           </p>
3302                         </td>
3303 <td>
3304                           <p>
3305                             yes
3306                           </p>
3307                         </td>
3308 </tr>
3309 <tr>
3310 <td>
3311                           <p><span><strong class="command">notify</strong></span></p>
3312                         </td>
3313 <td>
3314                           <p>
3315                             yes
3316                           </p>
3317                         </td>
3318 <td>
3319                           <p>
3320                             no
3321                           </p>
3322                         </td>
3323 <td>
3324                           <p>
3325                             yes
3326                           </p>
3327                         </td>
3328 </tr>
3329 <tr>
3330 <td>
3331                           <p><span><strong class="command">refresh</strong></span></p>
3332                         </td>
3333 <td>
3334                           <p>
3335                             no
3336                           </p>
3337                         </td>
3338 <td>
3339                           <p>
3340                             yes
3341                           </p>
3342                         </td>
3343 <td>
3344                           <p>
3345                             no
3346                           </p>
3347                         </td>
3348 </tr>
3349 <tr>
3350 <td>
3351                           <p><span><strong class="command">passive</strong></span></p>
3352                         </td>
3353 <td>
3354                           <p>
3355                             no
3356                           </p>
3357                         </td>
3358 <td>
3359                           <p>
3360                             no
3361                           </p>
3362                         </td>
3363 <td>
3364                           <p>
3365                             no
3366                           </p>
3367                         </td>
3368 </tr>
3369 <tr>
3370 <td>
3371                           <p><span><strong class="command">notify-passive</strong></span></p>
3372                         </td>
3373 <td>
3374                           <p>
3375                             no
3376                           </p>
3377                         </td>
3378 <td>
3379                           <p>
3380                             no
3381                           </p>
3382                         </td>
3383 <td>
3384                           <p>
3385                             yes
3386                           </p>
3387                         </td>
3388 </tr>
3389 </tbody>
3390 </table></div>
3391 <p>
3392                   Note that normal NOTIFY processing is not affected by
3393                   <span><strong class="command">dialup</strong></span>.
3394                 </p>
3395 </dd>
3396 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
3397 <dd><p>
3398                   In <acronym class="acronym">BIND</acronym> 8, this option
3399                   enabled simulating the obsolete DNS query type
3400                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3401                   IQUERY simulation.
3402                 </p></dd>
3403 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
3404 <dd><p>
3405                   This option is obsolete.
3406                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3407                   caused the server to attempt to fetch glue resource records
3408                   it
3409                   didn't have when constructing the additional
3410                   data section of a response.  This is now considered a bad
3411                   idea
3412                   and BIND 9 never does it.
3413                 </p></dd>
3414 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
3415 <dd><p>
3416                   When the nameserver exits due receiving SIGTERM,
3417                   flush or do not flush any pending zone writes.  The default
3418                   is
3419                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3420                 </p></dd>
3421 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
3422 <dd><p>
3423                   This option was incorrectly implemented
3424                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3425                   To achieve the intended effect
3426                   of
3427                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3428                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3429                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3430                 </p></dd>
3431 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
3432 <dd><p>
3433                   In BIND 8, this enables keeping of
3434                   statistics for every host that the name server interacts
3435                   with.
3436                   Not implemented in BIND 9.
3437                 </p></dd>
3438 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
3439 <dd><p>
3440                   <span class="emphasis"><em>This option is obsolete</em></span>.
3441                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3442                   determine whether a transaction log was
3443                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3444                   log whenever possible.  If you need to disable outgoing
3445                   incremental zone
3446                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3447                 </p></dd>
3448 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
3449 <dd><p>
3450                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3451                   responses the server will only add records to the authority
3452                   and additional data sections when they are required (e.g.
3453                   delegations, negative responses).  This may improve the
3454                   performance of the server.
3455                   The default is <strong class="userinput"><code>no</code></strong>.
3456                 </p></dd>
3457 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
3458 <dd><p>
3459                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3460                   a domain name to have multiple CNAME records in violation of
3461                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3462                   always strictly enforces the CNAME rules both in master
3463                   files and dynamic updates.
3464                 </p></dd>
3465 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
3466 <dd>
3467 <p>
3468                   If <strong class="userinput"><code>yes</code></strong> (the default),
3469                   DNS NOTIFY messages are sent when a zone the server is
3470                   authoritative for
3471                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3472                   sent to the
3473                   servers listed in the zone's NS records (except the master
3474                   server identified
3475                   in the SOA MNAME field), and to any servers listed in the
3476                   <span><strong class="command">also-notify</strong></span> option.
3477                 </p>
3478 <p>
3479                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3480                   sent
3481                   for master zones.
3482                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3483                   to
3484                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3485                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3486                 </p>
3487 <p>
3488                   The <span><strong class="command">notify</strong></span> option may also be
3489                   specified in the <span><strong class="command">zone</strong></span>
3490                   statement,
3491                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3492                   It would only be necessary to turn off this option if it
3493                   caused slaves
3494                   to crash.
3495                 </p>
3496 </dd>
3497 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3498 <dd><p>
3499                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3500                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3501                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3502                   supposed to contain the name of the ultimate master.
3503                   Sometimes, however, a slave is listed as the SOA MNAME in
3504                   hidden master configurations and in that case you would
3505                   want the ultimate master to still send NOTIFY messages to
3506                   all the nameservers listed in the NS RRset.
3507                 </p></dd>
3508 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3509 <dd><p>
3510                   If <strong class="userinput"><code>yes</code></strong>, and a
3511                   DNS query requests recursion, then the server will attempt
3512                   to do
3513                   all the work required to answer the query. If recursion is
3514                   off
3515                   and the server does not already know the answer, it will
3516                   return a
3517                   referral response. The default is
3518                   <strong class="userinput"><code>yes</code></strong>.
3519                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3520                   clients from getting data from the server's cache; it only
3521                   prevents new data from being cached as an effect of client
3522                   queries.
3523                   Caching may still occur as an effect the server's internal
3524                   operation, such as NOTIFY address lookups.
3525                   See also <span><strong class="command">fetch-glue</strong></span> above.
3526                 </p></dd>
3527 <dt><span class="term"><span><strong class="command">request-nsid</strong></span></span></dt>
3528 <dd><p>
3529                   If <strong class="userinput"><code>yes</code></strong>, then an empty EDNS(0)
3530                   NSID (Name Server Identifier) option is sent with all
3531                   queries to authoritative name servers during iterative
3532                   resolution. If the authoritative server returns an NSID
3533                   option in its response, then its contents are logged in
3534                   the <span><strong class="command">resolver</strong></span> category at level
3535                   <span><strong class="command">info</strong></span>.
3536                   The default is <strong class="userinput"><code>no</code></strong>.
3537                 </p></dd>
3538 <dt><span class="term"><span><strong class="command">request-sit</strong></span></span></dt>
3539 <dd><p>
3540                   If <strong class="userinput"><code>yes</code></strong>, then a SIT (Source
3541                   Identity Token) EDNS option is sent along with
3542                   the query.  If the resolver has previously talked
3543                   to the server, the SIT returned in the previous
3544                   transaction is sent. This is used by the server
3545                   to determine whether the resolver has talked to
3546                   it before. A resolver sending the correct SIT is
3547                   assumed not to be an off-path attacker sending a
3548                   spoofed-source query; the query is therefore
3549                   unlikely to be part of a reflection/amplification
3550                   attack, so resolvers sending a correct SIT option
3551                   are not subject to response rate limiting (RRL).
3552                   Resolvers which do not send a correct SIT option
3553                   may be limited to receiving smaller responses via
3554                   the <span><strong class="command">nosit-udp-size</strong></span> option.
3555                 </p></dd>
3556 <dt><span class="term"><span><strong class="command">sit-secret</strong></span></span></dt>
3557 <dd><p>
3558                   If set, this is a shared secret used for generating
3559                   and verifying Source Identity Token EDNS options
3560                   within a anycast cluster.  If not set the system
3561                   will generate a random secret at startup.  The
3562                   shared secret is encoded as a hex string and needs
3563                   to be 128 bits for AES128, 160 bits for SHA1 and
3564                   256 bits for SHA256.
3565                 </p></dd>
3566 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3567 <dd>
3568 <p>
3569                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3570                   cause the server to send NS records along with the SOA
3571                   record for negative
3572                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3573                 </p>
3574 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3575 <h3 class="title">Note</h3>
3576 <p>
3577                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3578                     9.
3579                   </p>
3580 </div>
3581 </dd>
3582 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3583 <dd><p>
3584                   <span class="emphasis"><em>This option is obsolete</em></span>.
3585                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3586                   IDs from a pool.
3587                 </p></dd>
3588 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3589 <dd><p>
3590                   <span class="emphasis"><em>This option is obsolete</em></span>.
3591                   If you need to disable IXFR to a particular server or
3592                   servers, see
3593                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3594                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3595             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3596             Usage&#8221;</a>.
3597                   See also
3598                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3599                 </p></dd>
3600 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3601 <dd><p>
3602                   See the description of
3603                   <span><strong class="command">provide-ixfr</strong></span> in
3604                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3605             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3606             Usage&#8221;</a>.
3607                 </p></dd>
3608 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3609 <dd><p>
3610                   See the description of
3611                   <span><strong class="command">request-ixfr</strong></span> in
3612                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3613             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3614             Usage&#8221;</a>.
3615                 </p></dd>
3616 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3617 <dd><p>
3618                   This option was used in <acronym class="acronym">BIND</acronym>
3619                   8 to make
3620                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3621                   as a space or tab character,
3622                   to facilitate loading of zone files on a UNIX system that
3623                   were generated
3624                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3625                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3626                   are always accepted,
3627                   and the option is ignored.
3628                 </p></dd>
3629 <dt>
3630 <span class="term"><span><strong class="command">additional-from-auth</strong></span>, </span><span class="term"><span><strong class="command">additional-from-cache</strong></span></span>
3631 </dt>
3632 <dd>
3633 <p>
3634                   These options control the behavior of an authoritative
3635                   server when
3636                   answering queries which have additional data, or when
3637                   following CNAME
3638                   and DNAME chains.
3639                 </p>
3640 <p>
3641                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3642                   (the default) and a
3643                   query is being answered from authoritative data (a zone
3644                   configured into the server), the additional data section of
3645                   the
3646                   reply will be filled in using data from other authoritative
3647                   zones
3648                   and from the cache.  In some situations this is undesirable,
3649                   such
3650                   as when there is concern over the correctness of the cache,
3651                   or
3652                   in servers where slave zones may be added and modified by
3653                   untrusted third parties.  Also, avoiding
3654                   the search for this additional data will speed up server
3655                   operations
3656                   at the possible expense of additional queries to resolve
3657                   what would
3658                   otherwise be provided in the additional section.
3659                 </p>
3660 <p>
3661                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3662                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3663                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3664                   if known, even though they are not in the example.com zone.
3665                   Setting these options to <span><strong class="command">no</strong></span>
3666                   disables this behavior and makes
3667                   the server only search for additional data in the zone it
3668                   answers from.
3669                 </p>
3670 <p>
3671                   These options are intended for use in authoritative-only
3672                   servers, or in authoritative-only views.  Attempts to set
3673                   them to <span><strong class="command">no</strong></span> without also
3674                   specifying
3675                   <span><strong class="command">recursion no</strong></span> will cause the
3676                   server to
3677                   ignore the options and log a warning message.
3678                 </p>
3679 <p>
3680                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3681                   disables the use of the cache not only for additional data
3682                   lookups
3683                   but also when looking up the answer.  This is usually the
3684                   desired
3685                   behavior in an authoritative-only server where the
3686                   correctness of
3687                   the cached data is an issue.
3688                 </p>
3689 <p>
3690                   When a name server is non-recursively queried for a name
3691                   that is not
3692                   below the apex of any served zone, it normally answers with
3693                   an
3694                   "upwards referral" to the root servers or the servers of
3695                   some other
3696                   known parent of the query name.  Since the data in an
3697                   upwards referral
3698                   comes from the cache, the server will not be able to provide
3699                   upwards
3700                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3701                   has been specified.  Instead, it will respond to such
3702                   queries
3703                   with REFUSED.  This should not cause any problems since
3704                   upwards referrals are not required for the resolution
3705                   process.
3706                 </p>
3707 </dd>
3708 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3709 <dd>
3710 <p>
3711                   If <strong class="userinput"><code>yes</code></strong>, then an
3712                   IPv4-mapped IPv6 address will match any address match
3713                   list entries that match the corresponding IPv4 address.
3714                 </p>
3715 <p>
3716                   This option was introduced to work around a kernel quirk
3717                   in some operating systems that causes IPv4 TCP
3718                   connections, such as zone transfers, to be accepted on an
3719                   IPv6 socket using mapped addresses.  This caused address
3720                   match lists designed for IPv4 to fail to match.  However,
3721                   <span><strong class="command">named</strong></span> now solves this problem
3722                   internally.  The use of this option is discouraged.
3723                 </p>
3724 </dd>
3725 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3726 <dd>
3727 <p>
3728                   This option is only available when
3729                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3730                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3731                   "configure" command line.  It is intended to help the
3732                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3733                   to DNS clients unless they have connections to the IPv6
3734                   Internet.  This is not recommended unless absolutely
3735                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3736                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3737                   may also be specified in <span><strong class="command">view</strong></span> statements
3738                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3739                   option.
3740                 </p>
3741 <p>
3742                   If <strong class="userinput"><code>yes</code></strong>,
3743                   the DNS client is at an IPv4 address, in <span><strong class="command">filter-aaaa</strong></span>,
3744                   and if the response does not include DNSSEC signatures,
3745                   then all AAAA records are deleted from the response.
3746                   This filtering applies to all responses and not only
3747                   authoritative responses.
3748                 </p>
3749 <p>
3750                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3751                   then AAAA records are deleted even when DNSSEC is enabled.
3752                   As suggested by the name, this makes the response not verify,
3753                   because the DNSSEC protocol is designed detect deletions.
3754                 </p>
3755 <p>
3756                   This mechanism can erroneously cause other servers to
3757                   not give AAAA records to their clients.
3758                   A recursing server with both IPv6 and IPv4 network connections
3759                   that queries an authoritative server using this mechanism
3760                   via IPv4 will be denied AAAA records even if its client is
3761                   using IPv6.
3762                 </p>
3763 <p>
3764                   This mechanism is applied to authoritative as well as
3765                   non-authoritative records.
3766                   A client using IPv4 that is not allowed recursion can
3767                   erroneously be given AAAA records because the server is not
3768                   allowed to check for A records.
3769                 </p>
3770 <p>
3771                   Some AAAA records are given to IPv4 clients in glue records.
3772                   IPv4 clients that are servers can then erroneously
3773                   answer requests for AAAA records received via IPv4.
3774                 </p>
3775 </dd>
3776 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v6</strong></span></span></dt>
3777 <dd><p>
3778                   Identical to <span><strong class="command">filter-aaaa-on-v4</strong></span>,
3779                   except it filters AAAA responses to queries from IPv6
3780                   clients instead of IPv4 clients.  To filter all
3781                   responses, set both options to <strong class="userinput"><code>yes</code></strong>.
3782                 </p></dd>
3783 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3784 <dd>
3785 <p>
3786                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new
3787                   version of a master zone from its zone file or receives a
3788                   new version of a slave file via zone transfer, it will
3789                   compare the new version to the previous one and calculate
3790                   a set of differences.  The differences are then logged in
3791                   the zone's journal file such that the changes can be
3792                   transmitted to downstream slaves as an incremental zone
3793                   transfer.
3794                 </p>
3795 <p>
3796                   By allowing incremental zone transfers to be used for
3797                   non-dynamic zones, this option saves bandwidth at the
3798                   expense of increased CPU and memory consumption at the
3799                   master.
3800                   In particular, if the new version of a zone is completely
3801                   different from the previous one, the set of differences
3802                   will be of a size comparable to the combined size of the
3803                   old and new zone version, and the server will need to
3804                   temporarily allocate memory to hold this complete
3805                   difference set.
3806                 </p>
3807 <p><span><strong class="command">ixfr-from-differences</strong></span>
3808                   also accepts <span><strong class="command">master</strong></span> and
3809                   <span><strong class="command">slave</strong></span> at the view and options
3810                   levels which causes
3811                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3812                   all <span><strong class="command">master</strong></span> or
3813                   <span><strong class="command">slave</strong></span> zones respectively.
3814                   It is off by default.
3815                 </p>
3816 </dd>
3817 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3818 <dd><p>
3819                   This should be set when you have multiple masters for a zone
3820                   and the
3821                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3822                   not log
3823                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3824                   currently
3825                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3826                 </p></dd>
3827 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3828 <dd><p>
3829                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3830                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3831                   The default is <strong class="userinput"><code>yes</code></strong>.
3832                 </p></dd>
3833 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3834 <dd><p>
3835                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3836                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3837                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3838                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3839                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3840                   DNSSEC validation is enabled, and a default
3841                   trust-anchor for the DNS root zone is used.  If set to
3842                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3843                   but a trust anchor must be manually configured using
3844                   a <span><strong class="command">trusted-keys</strong></span> or
3845                   <span><strong class="command">managed-keys</strong></span> statement.  The default
3846                   is <strong class="userinput"><code>yes</code></strong>.
3847                 </p></dd>
3848 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3849 <dd><p>
3850                   Accept expired signatures when verifying DNSSEC signatures.
3851                   The default is <strong class="userinput"><code>no</code></strong>.
3852                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3853                   leaves <span><strong class="command">named</strong></span> vulnerable to
3854                   replay attacks.
3855                 </p></dd>
3856 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3857 <dd><p>
3858                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3859                   starts.
3860                   If <span><strong class="command">querylog</strong></span> is not specified,
3861                   then the query logging
3862                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3863                 </p></dd>
3864 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3865 <dd>
3866 <p>
3867                   This option is used to restrict the character set and syntax
3868                   of
3869                   certain domain names in master files and/or DNS responses
3870                   received
3871                   from the network.  The default varies according to usage
3872                   area.  For
3873                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3874                   For <span><strong class="command">slave</strong></span> zones the default
3875                   is <span><strong class="command">warn</strong></span>.
3876                   For answers received from the network (<span><strong class="command">response</strong></span>)
3877                   the default is <span><strong class="command">ignore</strong></span>.
3878                 </p>
3879 <p>
3880                   The rules for legal hostnames and mail domains are derived
3881                   from RFC 952 and RFC 821 as modified by RFC 1123.
3882                 </p>
3883 <p><span><strong class="command">check-names</strong></span>
3884                   applies to the owner names of A, AAAA and MX records.
3885                   It also applies to the domain names in the RDATA of NS, SOA,
3886                   MX, and SRV records.
3887                   It also applies to the RDATA of PTR records where the owner
3888                   name indicated that it is a reverse lookup of a hostname
3889                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3890                 </p>
3891 </dd>
3892 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3893 <dd><p>
3894                   Check master zones for records that are treated as different
3895                   by DNSSEC but are semantically equal in plain DNS.  The
3896                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3897                   values are <span><strong class="command">fail</strong></span> and
3898                   <span><strong class="command">ignore</strong></span>.
3899                 </p></dd>
3900 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3901 <dd><p>
3902                   Check whether the MX record appears to refer to a IP address.
3903                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3904                   values are <span><strong class="command">fail</strong></span> and
3905                   <span><strong class="command">ignore</strong></span>.
3906                 </p></dd>
3907 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3908 <dd><p>
3909                   This option is used to check for non-terminal wildcards.
3910                   The use of non-terminal wildcards is almost always as a
3911                   result of a failure
3912                   to understand the wildcard matching algorithm (RFC 1034).
3913                   This option
3914                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3915                   for non-terminal wildcards and issue a warning.
3916                 </p></dd>
3917 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3918 <dd>
3919 <p>
3920                   Perform post load zone integrity checks on master
3921                   zones.  This checks that MX and SRV records refer
3922                   to address (A or AAAA) records and that glue
3923                   address records exist for delegated zones.  For
3924                   MX and SRV records only in-zone hostnames are
3925                   checked (for out-of-zone hostnames use
3926                   <span><strong class="command">named-checkzone</strong></span>).
3927                   For NS records only names below top of zone are
3928                   checked (for out-of-zone names and glue consistency
3929                   checks use <span><strong class="command">named-checkzone</strong></span>).
3930                   The default is <span><strong class="command">yes</strong></span>.
3931                 </p>
3932 <p>
3933                   The use of the SPF record for publishing Sender
3934                   Policy Framework is deprecated as the migration
3935                   from using TXT records to SPF records was abandoned.
3936                   Enabling this option also checks that a TXT Sender
3937                   Policy Framework record exists (starts with "v=spf1")
3938                   if there is an SPF record. Warnings are emitted if the
3939                   TXT record does not exist and can be suppressed with
3940                   <span><strong class="command">check-spf</strong></span>.
3941                 </p>
3942 </dd>
3943 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3944 <dd><p>
3945                   If <span><strong class="command">check-integrity</strong></span> is set then
3946                   fail, warn or ignore MX records that refer
3947                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3948                 </p></dd>
3949 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3950 <dd><p>
3951                   If <span><strong class="command">check-integrity</strong></span> is set then
3952                   fail, warn or ignore SRV records that refer
3953                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3954                 </p></dd>
3955 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3956 <dd><p>
3957                   When performing integrity checks, also check that
3958                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3959                 </p></dd>
3960 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
3961 <dd><p>
3962                   If <span><strong class="command">check-integrity</strong></span> is set then
3963                   check that there is a TXT Sender Policy Framework
3964                   record present (starts with "v=spf1") if there is an
3965                   SPF record present. The default is
3966                   <span><strong class="command">warn</strong></span>.
3967                 </p></dd>
3968 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3969 <dd><p>
3970                   When returning authoritative negative responses to
3971                   SOA queries set the TTL of the SOA record returned in
3972                   the authority section to zero.
3973                   The default is <span><strong class="command">yes</strong></span>.
3974                 </p></dd>
3975 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3976 <dd><p>
3977                   When caching a negative response to a SOA query
3978                   set the TTL to zero.
3979                   The default is <span><strong class="command">no</strong></span>.
3980                 </p></dd>
3981 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3982 <dd>
3983 <p>
3984                   When set to the default value of <code class="literal">yes</code>,
3985                   check the KSK bit in each key to determine how the key
3986                   should be used when generating RRSIGs for a secure zone.
3987                 </p>
3988 <p>
3989                   Ordinarily, zone-signing keys (that is, keys without the
3990                   KSK bit set) are used to sign the entire zone, while
3991                   key-signing keys (keys with the KSK bit set) are only
3992                   used to sign the DNSKEY RRset at the zone apex.
3993                   However, if this option is set to <code class="literal">no</code>,
3994                   then the KSK bit is ignored; KSKs are treated as if they
3995                   were ZSKs and are used to sign the entire zone.  This is
3996                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3997                   command line option.
3998                 </p>
3999 <p>
4000                   When this option is set to <code class="literal">yes</code>, there
4001                   must be at least two active keys for every algorithm
4002                   represented in the DNSKEY RRset: at least one KSK and one
4003                   ZSK per algorithm.  If there is any algorithm for which
4004                   this requirement is not met, this option will be ignored
4005                   for that algorithm.
4006                 </p>
4007 </dd>
4008 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
4009 <dd>
4010 <p>
4011                   When this option and <span><strong class="command">update-check-ksk</strong></span>
4012                   are both set to <code class="literal">yes</code>, only key-signing
4013                   keys (that is, keys with the KSK bit set) will be used
4014                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
4015                   keys (keys without the KSK bit set) will be used to sign
4016                   the remainder of the zone, but not the DNSKEY RRset.
4017                   This is similar to the
4018                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
4019                 </p>
4020 <p>
4021                   The default is <span><strong class="command">no</strong></span>.  If
4022                   <span><strong class="command">update-check-ksk</strong></span> is set to
4023                   <code class="literal">no</code>, this option is ignored.
4024                 </p>
4025 </dd>
4026 <dt><span class="term"><span><strong class="command">dnssec-loadkeys-interval</strong></span></span></dt>
4027 <dd><p>
4028                   When a zone is configured with <span><strong class="command">auto-dnssec
4029                   maintain;</strong></span> its key repository must be checked
4030                   periodically to see if any new keys have been added
4031                   or any existing keys' timing metadata has been updated
4032                   (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
4033                   <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The
4034                   <span><strong class="command">dnssec-loadkeys-interval</strong></span> option
4035                   sets the frequency of automatic repository checks, in
4036                   minutes.  The default is <code class="literal">60</code> (1 hour),
4037                   the minimum is <code class="literal">1</code> (1 minute), and the
4038                   maximum is <code class="literal">1440</code> (24 hours); any higher
4039                   value is silently reduced.
4040                 </p></dd>
4041 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
4042 <dd><p>
4043                   Try to refresh the zone using TCP if UDP queries fail.
4044                   For BIND 8 compatibility, the default is
4045                   <span><strong class="command">yes</strong></span>.
4046                 </p></dd>
4047 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
4048 <dd>
4049 <p>
4050                   Allow a dynamic zone to transition from secure to
4051                   insecure (i.e., signed to unsigned) by deleting all
4052                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
4053                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
4054                   at the zone apex is deleted, all RRSIG and NSEC records
4055                   will be removed from the zone as well.
4056                 </p>
4057 <p>
4058                   If the zone uses NSEC3, then it is also necessary to
4059                   delete the NSEC3PARAM RRset from the zone apex; this will
4060                   cause the removal of all corresponding NSEC3 records.
4061                   (It is expected that this requirement will be eliminated
4062                   in a future release.)
4063                 </p>
4064 <p>
4065                   Note that if a zone has been configured with
4066                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
4067                   private keys remain accessible in the key repository,
4068                   then the zone will be automatically signed again the
4069                   next time <span><strong class="command">named</strong></span> is started.
4070                 </p>
4071 </dd>
4072 </dl></div>
4073 </div>
4074 <div class="sect3" lang="en">
4075 <div class="titlepage"><div><div><h4 class="title">
4076 <a name="id2584144"></a>Forwarding</h4></div></div></div>
4077 <p>
4078             The forwarding facility can be used to create a large site-wide
4079             cache on a few servers, reducing traffic over links to external
4080             name servers. It can also be used to allow queries by servers that
4081             do not have direct access to the Internet, but wish to look up
4082             exterior
4083             names anyway. Forwarding occurs only on those queries for which
4084             the server is not authoritative and does not have the answer in
4085             its cache.
4086           </p>
4087 <div class="variablelist"><dl>
4088 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
4089 <dd><p>
4090                   This option is only meaningful if the
4091                   forwarders list is not empty. A value of <code class="varname">first</code>,
4092                   the default, causes the server to query the forwarders
4093                   first &#8212; and
4094                   if that doesn't answer the question, the server will then
4095                   look for
4096                   the answer itself. If <code class="varname">only</code> is
4097                   specified, the
4098                   server will only query the forwarders.
4099                 </p></dd>
4100 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
4101 <dd><p>
4102                   Specifies the IP addresses to be used
4103                   for forwarding. The default is the empty list (no
4104                   forwarding).
4105                 </p></dd>
4106 </dl></div>
4107 <p>
4108             Forwarding can also be configured on a per-domain basis, allowing
4109             for the global forwarding options to be overridden in a variety
4110             of ways. You can set particular domains to use different
4111             forwarders,
4112             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
4113             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
4114             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
4115             Statement Grammar&#8221;</a>.
4116           </p>
4117 </div>
4118 <div class="sect3" lang="en">
4119 <div class="titlepage"><div><div><h4 class="title">
4120 <a name="id2584202"></a>Dual-stack Servers</h4></div></div></div>
4121 <p>
4122             Dual-stack servers are used as servers of last resort to work
4123             around
4124             problems in reachability due the lack of support for either IPv4
4125             or IPv6
4126             on the host machine.
4127           </p>
4128 <div class="variablelist"><dl>
4129 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
4130 <dd><p>
4131                   Specifies host names or addresses of machines with access to
4132                   both IPv4 and IPv6 transports. If a hostname is used, the
4133                   server must be able
4134                   to resolve the name using only the transport it has.  If the
4135                   machine is dual
4136                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
4137                   access to a transport has been disabled on the command line
4138                   (e.g. <span><strong class="command">named -4</strong></span>).
4139                 </p></dd>
4140 </dl></div>
4141 </div>
4142 <div class="sect3" lang="en">
4143 <div class="titlepage"><div><div><h4 class="title">
4144 <a name="access_control"></a>Access Control</h4></div></div></div>
4145 <p>
4146             Access to the server can be restricted based on the IP address
4147             of the requesting system. See <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a> for
4148             details on how to specify IP address lists.
4149           </p>
4150 <div class="variablelist"><dl>
4151 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
4152 <dd><p>
4153                   Specifies which hosts are allowed to
4154                   notify this server, a slave, of zone changes in addition
4155                   to the zone masters.
4156                   <span><strong class="command">allow-notify</strong></span> may also be
4157                   specified in the
4158                   <span><strong class="command">zone</strong></span> statement, in which case
4159                   it overrides the
4160                   <span><strong class="command">options allow-notify</strong></span>
4161                   statement.  It is only meaningful
4162                   for a slave zone.  If not specified, the default is to
4163                   process notify messages
4164                   only from a zone's master.
4165                 </p></dd>
4166 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
4167 <dd>
4168 <p>
4169                   Specifies which hosts are allowed to ask ordinary
4170                   DNS questions. <span><strong class="command">allow-query</strong></span> may
4171                   also be specified in the <span><strong class="command">zone</strong></span>
4172                   statement, in which case it overrides the
4173                   <span><strong class="command">options allow-query</strong></span> statement.
4174                   If not specified, the default is to allow queries
4175                   from all hosts.
4176                 </p>
4177 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4178 <h3 class="title">Note</h3>
4179 <p>
4180                     <span><strong class="command">allow-query-cache</strong></span> is now
4181                     used to specify access to the cache.
4182                   </p>
4183 </div>
4184 </dd>
4185 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
4186 <dd>
4187 <p>
4188                   Specifies which local addresses can accept ordinary
4189                   DNS questions. This makes it possible, for instance,
4190                   to allow queries on internal-facing interfaces but
4191                   disallow them on external-facing ones, without
4192                   necessarily knowing the internal network's addresses.
4193                 </p>
4194 <p>
4195                   Note that <span><strong class="command">allow-query-on</strong></span> is only
4196                   checked for queries that are permitted by
4197                   <span><strong class="command">allow-query</strong></span>.  A query must be
4198                   allowed by both ACLs, or it will be refused.
4199                 </p>
4200 <p>
4201                   <span><strong class="command">allow-query-on</strong></span> may
4202                   also be specified in the <span><strong class="command">zone</strong></span>
4203                   statement, in which case it overrides the
4204                   <span><strong class="command">options allow-query-on</strong></span> statement.
4205                 </p>
4206 <p>
4207                   If not specified, the default is to allow queries
4208                   on all addresses.
4209                 </p>
4210 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4211 <h3 class="title">Note</h3>
4212 <p>
4213                     <span><strong class="command">allow-query-cache</strong></span> is
4214                     used to specify access to the cache.
4215                   </p>
4216 </div>
4217 </dd>
4218 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
4219 <dd><p>
4220                   Specifies which hosts are allowed to get answers
4221                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
4222                   is not set then <span><strong class="command">allow-recursion</strong></span>
4223                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
4224                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
4225                   set in which case <span><strong class="command">none;</strong></span> is used,
4226                   otherwise the default (<span><strong class="command">localnets;</strong></span>
4227                   <span><strong class="command">localhost;</strong></span>) is used.
4228                 </p></dd>
4229 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
4230 <dd><p>
4231                   Specifies which local addresses can give answers
4232                   from the cache.  If not specified, the default is
4233                   to allow cache queries on any address,
4234                   <span><strong class="command">localnets</strong></span> and
4235                   <span><strong class="command">localhost</strong></span>.
4236                 </p></dd>
4237 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
4238 <dd><p>
4239                   Specifies which hosts are allowed to make recursive
4240                   queries through this server. If
4241                   <span><strong class="command">allow-recursion</strong></span> is not set
4242                   then <span><strong class="command">allow-query-cache</strong></span> is
4243                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
4244                   is used if set, otherwise the default
4245                   (<span><strong class="command">localnets;</strong></span>
4246                   <span><strong class="command">localhost;</strong></span>) is used.
4247                 </p></dd>
4248 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
4249 <dd><p>
4250                   Specifies which local addresses can accept recursive
4251                   queries.  If not specified, the default is to allow
4252                   recursive queries on all addresses.
4253                 </p></dd>
4254 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
4255 <dd><p>
4256                   Specifies which hosts are allowed to
4257                   submit Dynamic DNS updates for master zones. The default is
4258                   to deny
4259                   updates from all hosts.  Note that allowing updates based
4260                   on the requestor's IP address is insecure; see
4261                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
4262                 </p></dd>
4263 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
4264 <dd>
4265 <p>
4266                   Specifies which hosts are allowed to
4267                   submit Dynamic DNS updates to slave zones to be forwarded to
4268                   the
4269                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
4270                   which
4271                   means that no update forwarding will be performed.  To
4272                   enable
4273                   update forwarding, specify
4274                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
4275                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
4276                   <strong class="userinput"><code>{ any; }</code></strong> is usually
4277                   counterproductive, since
4278                   the responsibility for update access control should rest
4279                   with the
4280                   master server, not the slaves.
4281                 </p>
4282 <p>
4283                   Note that enabling the update forwarding feature on a slave
4284                   server
4285                   may expose master servers relying on insecure IP address
4286                   based
4287                   access control to attacks; see <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a>
4288                   for more details.
4289                 </p>
4290 </dd>
4291 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
4292 <dd><p>
4293                   This option was introduced for the smooth transition from
4294                   AAAA
4295                   to A6 and from "nibble labels" to binary labels.
4296                   However, since both A6 and binary labels were then
4297                   deprecated,
4298                   this option was also deprecated.
4299                   It is now ignored with some warning messages.
4300                 </p></dd>
4301 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
4302 <dd><p>
4303                   Specifies which hosts are allowed to
4304                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
4305                   also be specified in the <span><strong class="command">zone</strong></span>
4306                   statement, in which
4307                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
4308                   If not specified, the default is to allow transfers to all
4309                   hosts.
4310                 </p></dd>
4311 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
4312 <dd><p>
4313                   Specifies a list of addresses that the
4314                   server will not accept queries from or use to resolve a
4315                   query. Queries
4316                   from these addresses will not be responded to. The default
4317                   is <strong class="userinput"><code>none</code></strong>.
4318                 </p></dd>
4319 <dt><span class="term"><span><strong class="command">filter-aaaa</strong></span></span></dt>
4320 <dd><p>
4321                   Specifies a list of addresses to which
4322                   <span><strong class="command">filter-aaaa-on-v4</strong></span>
4323                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
4324                 </p></dd>
4325 <dt><span class="term"><span><strong class="command">no-case-compress</strong></span></span></dt>
4326 <dd>
4327 <p>
4328                   Specifies a list of addresses which require responses
4329                   to use case-insensitive compression.  This ACL can be
4330                   used when <span><strong class="command">named</strong></span> needs to work with
4331                   clients that do not comply with the requirement in RFC
4332                   1034 to use case-insensitive name comparisons when
4333                   checking for matching domain names.
4334                 </p>
4335 <p>
4336                   If left undefined, the ACL defaults to
4337                   <span><strong class="command">none</strong></span>: case-insensitive compression
4338                   will be used for all clients.  If the ACL is defined and
4339                   matches a client, then case will be ignored when
4340                   compressing domain names in DNS responses sent to that
4341                   client.
4342                 </p>
4343 <p>
4344                   This can result in slightly smaller responses: if
4345                   a response contains the names "example.com" and
4346                   "example.COM", case-insensitive compression would treat
4347                   the second one as a duplicate.  It also ensures
4348                   that the case of the query name exactly matches the
4349                   case of the owner names of returned records, rather
4350                   than matching the case of the records entered in
4351                   the zone file.  This allows responses to exactly
4352                   match the query, which is required by some clients
4353                   due to incorrect use of case-sensitive comparisons.
4354                 </p>
4355 <p>
4356                   Case-insensitive compression is <span class="emphasis"><em>always</em></span>
4357                   used in AXFR and IXFR responses, regardless of whether
4358                   the client matches this ACL.
4359                 </p>
4360 <p>
4361                   There are circumstances in which <span><strong class="command">named</strong></span>
4362                   will not preserve the case of owner names of records:
4363                   if a zone file defines records of different types with
4364                   the same name, but the capitalization of the name is
4365                   different (e.g., "www.example.com/A" and
4366                   "WWW.EXAMPLE.COM/AAAA"), then all responses for that
4367                   name will use the <span class="emphasis"><em>first</em></span> version
4368                   of the name that was used in the zone file.  This
4369                   limitation may be addressed in a future release.  However,
4370                   domain names specified in the rdata of resource records
4371                   (i.e., records of type NS, MX, CNAME, etc) will always
4372                   have their case preserved unless the client matches this
4373                   ACL.
4374                 </p>
4375 </dd>
4376 <dt><span class="term"><span><strong class="command">resolver-query-timeout</strong></span></span></dt>
4377 <dd><p>
4378                   The amount of time the resolver will spend attempting
4379                   to resolve a recursive query before failing.  The default
4380                   and minimum is <code class="literal">10</code> and the maximum is
4381                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
4382                   will result in the default being used.
4383                 </p></dd>
4384 </dl></div>
4385 </div>
4386 <div class="sect3" lang="en">
4387 <div class="titlepage"><div><div><h4 class="title">
4388 <a name="id2584876"></a>Interfaces</h4></div></div></div>
4389 <p>
4390             The interfaces and ports that the server will answer queries
4391             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
4392             an optional port and an <code class="varname">address_match_list</code>
4393             of IPv4 addresses.  (IPv6 addresses are ignored, with a
4394             logged warning.)
4395             The server will listen on all interfaces allowed by the address
4396             match list. If a port is not specified, port 53 will be used.
4397           </p>
4398 <p>
4399             Multiple <span><strong class="command">listen-on</strong></span> statements are
4400             allowed.
4401             For example,
4402           </p>
4403 <pre class="programlisting">listen-on { 5.6.7.8; };
4404 listen-on port 1234 { !1.2.3.4; 1.2/16; };
4405 </pre>
4406 <p>
4407             will enable the name server on port 53 for the IP address
4408             5.6.7.8, and on port 1234 of an address on the machine in net
4409             1.2 that is not 1.2.3.4.
4410           </p>
4411 <p>
4412             If no <span><strong class="command">listen-on</strong></span> is specified, the
4413             server will listen on port 53 on all IPv4 interfaces.
4414           </p>
4415 <p>
4416             The <span><strong class="command">listen-on-v6</strong></span> option is used to
4417             specify the interfaces and the ports on which the server will
4418             listen for incoming queries sent using IPv6.  If not specified,
4419             the server will listen on port 53 on all IPv6 interfaces.
4420           </p>
4421 <p>
4422             When </p>
4423 <pre class="programlisting">{ any; }</pre>
4424 <p> is
4425             specified
4426             as the <code class="varname">address_match_list</code> for the
4427             <span><strong class="command">listen-on-v6</strong></span> option,
4428             the server does not bind a separate socket to each IPv6 interface
4429             address as it does for IPv4 if the operating system has enough API
4430             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
4431             3542).
4432             Instead, it listens on the IPv6 wildcard address.
4433             If the system only has incomplete API support for IPv6, however,
4434             the behavior is the same as that for IPv4.
4435           </p>
4436 <p>
4437             A list of particular IPv6 addresses can also be specified, in
4438             which case
4439             the server listens on a separate socket for each specified
4440             address,
4441             regardless of whether the desired API is supported by the system.
4442             IPv4 addresses specified in <span><strong class="command">listen-on-v6</strong></span>
4443             will be ignored, with a logged warning.
4444           </p>
4445 <p>
4446             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
4447             be used.
4448             For example,
4449           </p>
4450 <pre class="programlisting">listen-on-v6 { any; };
4451 listen-on-v6 port 1234 { !2001:db8::/32; any; };
4452 </pre>
4453 <p>
4454             will enable the name server on port 53 for any IPv6 addresses
4455             (with a single wildcard socket),
4456             and on port 1234 of IPv6 addresses that is not in the prefix
4457             2001:db8::/32 (with separate sockets for each matched address.)
4458           </p>
4459 <p>
4460             To make the server not listen on any IPv6 address, use
4461           </p>
4462 <pre class="programlisting">listen-on-v6 { none; };
4463 </pre>
4464 </div>
4465 <div class="sect3" lang="en">
4466 <div class="titlepage"><div><div><h4 class="title">
4467 <a name="query_address"></a>Query Address</h4></div></div></div>
4468 <p>
4469             If the server doesn't know the answer to a question, it will
4470             query other name servers. <span><strong class="command">query-source</strong></span> specifies
4471             the address and port used for such queries. For queries sent over
4472             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
4473             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
4474             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
4475             will be used.
4476           </p>
4477 <p>
4478             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
4479             a random port number from a pre-configured
4480             range is picked up and will be used for each query.
4481             The port range(s) is that specified in
4482             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
4483             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
4484             options, excluding the ranges specified in
4485             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
4486             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
4487           </p>
4488 <p>
4489             The defaults of the <span><strong class="command">query-source</strong></span> and
4490             <span><strong class="command">query-source-v6</strong></span> options
4491             are:
4492           </p>
4493 <pre class="programlisting">query-source address * port *;
4494 query-source-v6 address * port *;
4495 </pre>
4496 <p>
4497             If <span><strong class="command">use-v4-udp-ports</strong></span> or
4498             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
4499             <span><strong class="command">named</strong></span> will check if the operating
4500             system provides a programming interface to retrieve the
4501             system's default range for ephemeral ports.
4502             If such an interface is available,
4503             <span><strong class="command">named</strong></span> will use the corresponding system
4504             default range; otherwise, it will use its own defaults:
4505          </p>
4506 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4507 use-v6-udp-ports { range 1024 65535; };
4508 </pre>
4509 <p>
4510             Note: make sure the ranges be sufficiently large for
4511             security.  A desirable size depends on various parameters,
4512             but we generally recommend it contain at least 16384 ports
4513             (14 bits of entropy).
4514             Note also that the system's default range when used may be
4515             too small for this purpose, and that the range may even be
4516             changed while <span><strong class="command">named</strong></span> is running; the new
4517             range will automatically be applied when <span><strong class="command">named</strong></span>
4518             is reloaded.
4519             It is encouraged to
4520             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
4521             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
4522             ranges are sufficiently large and are reasonably
4523             independent from the ranges used by other applications.
4524           </p>
4525 <p>
4526             Note: the operational configuration
4527             where <span><strong class="command">named</strong></span> runs may prohibit the use
4528             of some ports.  For example, UNIX systems will not allow
4529             <span><strong class="command">named</strong></span> running without a root privilege
4530             to use ports less than 1024.
4531             If such ports are included in the specified (or detected)
4532             set of query ports, the corresponding query attempts will
4533             fail, resulting in resolution failures or delay.
4534             It is therefore important to configure the set of ports
4535             that can be safely used in the expected operational environment.
4536           </p>
4537 <p>
4538             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4539             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
4540             are:
4541           </p>
4542 <pre class="programlisting">avoid-v4-udp-ports {};
4543 avoid-v6-udp-ports {};
4544 </pre>
4545 <p>
4546             Note: BIND 9.5.0 introduced
4547             the <span><strong class="command">use-queryport-pool</strong></span>
4548             option to support a pool of such random ports, but this
4549             option is now obsolete because reusing the same ports in
4550             the pool may not be sufficiently secure.
4551             For the same reason, it is generally strongly discouraged to
4552             specify a particular port for the
4553             <span><strong class="command">query-source</strong></span> or
4554             <span><strong class="command">query-source-v6</strong></span> options;
4555             it implicitly disables the use of randomized port numbers.
4556           </p>
4557 <div class="variablelist"><dl>
4558 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
4559 <dd><p>
4560                   This option is obsolete.
4561                 </p></dd>
4562 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
4563 <dd><p>
4564                   This option is obsolete.
4565                 </p></dd>
4566 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
4567 <dd><p>
4568                   This option is obsolete.
4569                 </p></dd>
4570 </dl></div>
4571 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4572 <h3 class="title">Note</h3>
4573 <p>
4574               The address specified in the <span><strong class="command">query-source</strong></span> option
4575               is used for both UDP and TCP queries, but the port applies only
4576               to UDP queries.  TCP queries always use a random
4577               unprivileged port.
4578             </p>
4579 </div>
4580 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4581 <h3 class="title">Note</h3>
4582 <p>
4583               Solaris 2.5.1 and earlier does not support setting the source
4584               address for TCP sockets.
4585             </p>
4586 </div>
4587 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4588 <h3 class="title">Note</h3>
4589 <p>
4590               See also <span><strong class="command">transfer-source</strong></span> and
4591               <span><strong class="command">notify-source</strong></span>.
4592             </p>
4593 </div>
4594 </div>
4595 <div class="sect3" lang="en">
4596 <div class="titlepage"><div><div><h4 class="title">
4597 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4598 <p>
4599             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4600             facilitate zone transfers
4601             and set limits on the amount of load that transfers place on the
4602             system. The following options apply to zone transfers.
4603           </p>
4604 <div class="variablelist"><dl>
4605 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
4606 <dd>
4607 <p>
4608                   Defines a global list of IP addresses of name servers
4609                   that are also sent NOTIFY messages whenever a fresh copy of
4610                   the
4611                   zone is loaded, in addition to the servers listed in the
4612                   zone's NS records.
4613                   This helps to ensure that copies of the zones will
4614                   quickly converge on stealth servers.
4615                   Optionally, a port may be specified with each
4616                   <span><strong class="command">also-notify</strong></span> address to send
4617                   the notify messages to a port other than the
4618                   default of 53.
4619                   An optional TSIG key can also be specified with each
4620                   address to cause the notify messages to be signed; this
4621                   can be useful when sending notifies to multiple views.
4622                   In place of explicit addresses, one or more named
4623                   <span><strong class="command">masters</strong></span> lists can be used.
4624                 </p>
4625 <p>
4626                   If an <span><strong class="command">also-notify</strong></span> list
4627                   is given in a <span><strong class="command">zone</strong></span> statement,
4628                   it will override
4629                   the <span><strong class="command">options also-notify</strong></span>
4630                   statement. When a <span><strong class="command">zone notify</strong></span>
4631                   statement
4632                   is set to <span><strong class="command">no</strong></span>, the IP
4633                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4634                   not be sent NOTIFY messages for that zone. The default is
4635                   the empty
4636                   list (no global notification list).
4637                 </p>
4638 </dd>
4639 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4640 <dd><p>
4641                   Inbound zone transfers running longer than
4642                   this many minutes will be terminated. The default is 120
4643                   minutes
4644                   (2 hours).  The maximum value is 28 days (40320 minutes).
4645                 </p></dd>
4646 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4647 <dd><p>
4648                   Inbound zone transfers making no progress
4649                   in this many minutes will be terminated. The default is 60
4650                   minutes
4651                   (1 hour).  The maximum value is 28 days (40320 minutes).
4652                 </p></dd>
4653 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4654 <dd><p>
4655                   Outbound zone transfers running longer than
4656                   this many minutes will be terminated. The default is 120
4657                   minutes
4658                   (2 hours).  The maximum value is 28 days (40320 minutes).
4659                 </p></dd>
4660 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4661 <dd><p>
4662                   Outbound zone transfers making no progress
4663                   in this many minutes will be terminated.  The default is 60
4664                   minutes (1
4665                   hour).  The maximum value is 28 days (40320 minutes).
4666                 </p></dd>
4667 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4668 <dd>
4669 <p>
4670                   Slave servers will periodically query master
4671                   servers to find out if zone serial numbers have
4672                   changed. Each such query uses a minute amount of
4673                   the slave server's network bandwidth.  To limit
4674                   the amount of bandwidth used, BIND 9 limits the
4675                   rate at which queries are sent.  The value of the
4676                   <span><strong class="command">serial-query-rate</strong></span> option, an
4677                   integer, is the maximum number of queries sent
4678                   per second.  The default is 20 per second.
4679                   The lowest possible rate is one per second; when set
4680                   to zero, it will be silently raised to one.
4681                 </p>
4682 <p>
4683                   In addition to controlling the rate SOA refresh
4684                   queries are issued at
4685                   <span><strong class="command">serial-query-rate</strong></span> also controls
4686                   the rate at which NOTIFY messages are sent from
4687                   both master and slave zones.
4688                 </p>
4689 </dd>
4690 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4691 <dd><p>
4692                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4693                   option
4694                   set the maximum number of concurrent serial number queries
4695                   allowed to be outstanding at any given time.
4696                   BIND 9 does not limit the number of outstanding
4697                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4698                   Instead, it limits the rate at which the queries are sent
4699                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4700                 </p></dd>
4701 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4702 <dd><p>
4703                   Zone transfers can be sent using two different formats,
4704                   <span><strong class="command">one-answer</strong></span> and
4705                   <span><strong class="command">many-answers</strong></span>.
4706                   The <span><strong class="command">transfer-format</strong></span> option is used
4707                   on the master server to determine which format it sends.
4708                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4709                   resource record transferred.
4710                   <span><strong class="command">many-answers</strong></span> packs as many resource
4711                   records as possible into a message.
4712                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4713                   only supported by relatively new slave servers,
4714                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4715                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4716                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4717                   recent Microsoft Windows nameservers.
4718                   The default is <span><strong class="command">many-answers</strong></span>.
4719                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4720                   per-server basis by using the <span><strong class="command">server</strong></span>
4721                   statement.
4722                 </p></dd>
4723 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4724 <dd><p>
4725                   The maximum number of inbound zone transfers
4726                   that can be running concurrently. The default value is <code class="literal">10</code>.
4727                   Increasing <span><strong class="command">transfers-in</strong></span> may
4728                   speed up the convergence
4729                   of slave zones, but it also may increase the load on the
4730                   local system.
4731                 </p></dd>
4732 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4733 <dd><p>
4734                   The maximum number of outbound zone transfers
4735                   that can be running concurrently. Zone transfer requests in
4736                   excess
4737                   of the limit will be refused. The default value is <code class="literal">10</code>.
4738                 </p></dd>
4739 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4740 <dd><p>
4741                   The maximum number of inbound zone transfers
4742                   that can be concurrently transferring from a given remote
4743                   name server.
4744                   The default value is <code class="literal">2</code>.
4745                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4746                   may
4747                   speed up the convergence of slave zones, but it also may
4748                   increase
4749                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4750                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4751                   of the <span><strong class="command">server</strong></span> statement.
4752                 </p></dd>
4753 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4754 <dd>
4755 <p><span><strong class="command">transfer-source</strong></span>
4756                   determines which local address will be bound to IPv4
4757                   TCP connections used to fetch zones transferred
4758                   inbound by the server.  It also determines the
4759                   source IPv4 address, and optionally the UDP port,
4760                   used for the refresh queries and forwarded dynamic
4761                   updates.  If not set, it defaults to a system
4762                   controlled value which will usually be the address
4763                   of the interface "closest to" the remote end. This
4764                   address must appear in the remote end's
4765                   <span><strong class="command">allow-transfer</strong></span> option for the
4766                   zone being transferred, if one is specified. This
4767                   statement sets the
4768                   <span><strong class="command">transfer-source</strong></span> for all zones,
4769                   but can be overridden on a per-view or per-zone
4770                   basis by including a
4771                   <span><strong class="command">transfer-source</strong></span> statement within
4772                   the <span><strong class="command">view</strong></span> or
4773                   <span><strong class="command">zone</strong></span> block in the configuration
4774                   file.
4775                 </p>
4776 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4777 <h3 class="title">Note</h3>
4778 <p>
4779                     Solaris 2.5.1 and earlier does not support setting the
4780                     source address for TCP sockets.
4781                   </p>
4782 </div>
4783 </dd>
4784 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4785 <dd><p>
4786                   The same as <span><strong class="command">transfer-source</strong></span>,
4787                   except zone transfers are performed using IPv6.
4788                 </p></dd>
4789 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4790 <dd>
4791 <p>
4792                   An alternate transfer source if the one listed in
4793                   <span><strong class="command">transfer-source</strong></span> fails and
4794                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4795                   set.
4796                 </p>
4797 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4798 <h3 class="title">Note</h3>
4799                   If you do not wish the alternate transfer source
4800                   to be used, you should set
4801                   <span><strong class="command">use-alt-transfer-source</strong></span>
4802                   appropriately and you should not depend upon
4803                   getting an answer back to the first refresh
4804                   query.
4805                 </div>
4806 </dd>
4807 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4808 <dd><p>
4809                   An alternate transfer source if the one listed in
4810                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4811                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4812                   set.
4813                 </p></dd>
4814 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4815 <dd><p>
4816                   Use the alternate transfer sources or not.  If views are
4817                   specified this defaults to <span><strong class="command">no</strong></span>
4818                   otherwise it defaults to
4819                   <span><strong class="command">yes</strong></span> (for BIND 8
4820                   compatibility).
4821                 </p></dd>
4822 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4823 <dd>
4824 <p><span><strong class="command">notify-source</strong></span>
4825                   determines which local source address, and
4826                   optionally UDP port, will be used to send NOTIFY
4827                   messages.  This address must appear in the slave
4828                   server's <span><strong class="command">masters</strong></span> zone clause or
4829                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4830                   statement sets the <span><strong class="command">notify-source</strong></span>
4831                   for all zones, but can be overridden on a per-zone or
4832                   per-view basis by including a
4833                   <span><strong class="command">notify-source</strong></span> statement within
4834                   the <span><strong class="command">zone</strong></span> or
4835                   <span><strong class="command">view</strong></span> block in the configuration
4836                   file.
4837                 </p>
4838 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4839 <h3 class="title">Note</h3>
4840 <p>
4841                     Solaris 2.5.1 and earlier does not support setting the
4842                     source address for TCP sockets.
4843                   </p>
4844 </div>
4845 </dd>
4846 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4847 <dd><p>
4848                   Like <span><strong class="command">notify-source</strong></span>,
4849                   but applies to notify messages sent to IPv6 addresses.
4850                 </p></dd>
4851 </dl></div>
4852 </div>
4853 <div class="sect3" lang="en">
4854 <div class="titlepage"><div><div><h4 class="title">
4855 <a name="id2586147"></a>UDP Port Lists</h4></div></div></div>
4856 <p>
4857             <span><strong class="command">use-v4-udp-ports</strong></span>,
4858             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4859             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4860             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4861             specify a list of IPv4 and IPv6 UDP ports that will be
4862             used or not used as source ports for UDP messages.
4863             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4864             available ports are determined.
4865             For example, with the following configuration
4866           </p>
4867 <pre class="programlisting">
4868 use-v6-udp-ports { range 32768 65535; };
4869 avoid-v6-udp-ports { 40000; range 50000 60000; };
4870 </pre>
4871 <p>
4872              UDP ports of IPv6 messages sent
4873              from <span><strong class="command">named</strong></span> will be in one
4874              of the following ranges: 32768 to 39999, 40001 to 49999,
4875              and 60001 to 65535.
4876            </p>
4877 <p>
4878              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4879              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4880              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4881              port that is blocked by your firewall or a port that is
4882              used by other applications;
4883              if a query went out with a source port blocked by a
4884              firewall, the
4885              answer would not get by the firewall and the name server would
4886              have to query again.
4887              Note: the desired range can also be represented only with
4888              <span><strong class="command">use-v4-udp-ports</strong></span> and
4889              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4890              <span><strong class="command">avoid-</strong></span> options are redundant in that
4891              sense; they are provided for backward compatibility and
4892              to possibly simplify the port specification.
4893            </p>
4894 </div>
4895 <div class="sect3" lang="en">
4896 <div class="titlepage"><div><div><h4 class="title">
4897 <a name="id2586206"></a>Operating System Resource Limits</h4></div></div></div>
4898 <p>
4899             The server's usage of many system resources can be limited.
4900             Scaled values are allowed when specifying resource limits.  For
4901             example, <span><strong class="command">1G</strong></span> can be used instead of
4902             <span><strong class="command">1073741824</strong></span> to specify a limit of
4903             one
4904             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4905             unlimited use, or the
4906             maximum available amount. <span><strong class="command">default</strong></span>
4907             uses the limit
4908             that was in force when the server was started. See the description
4909             of <span><strong class="command">size_spec</strong></span> in <a href="Bv9ARM.ch06.html#configuration_file_elements" title="Configuration File Elements">the section called &#8220;Configuration File Elements&#8221;</a>.
4910           </p>
4911 <p>
4912             The following options set operating system resource limits for
4913             the name server process.  Some operating systems don't support
4914             some or
4915             any of the limits. On such systems, a warning will be issued if
4916             the
4917             unsupported limit is used.
4918           </p>
4919 <div class="variablelist"><dl>
4920 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4921 <dd><p>
4922                   The maximum size of a core dump. The default
4923                   is <code class="literal">default</code>.
4924                 </p></dd>
4925 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4926 <dd><p>
4927                   The maximum amount of data memory the server
4928                   may use. The default is <code class="literal">default</code>.
4929                   This is a hard limit on server memory usage.
4930                   If the server attempts to allocate memory in excess of this
4931                   limit, the allocation will fail, which may in turn leave
4932                   the server unable to perform DNS service.  Therefore,
4933                   this option is rarely useful as a way of limiting the
4934                   amount of memory used by the server, but it can be used
4935                   to raise an operating system data size limit that is
4936                   too small by default.  If you wish to limit the amount
4937                   of memory used by the server, use the
4938                   <span><strong class="command">max-cache-size</strong></span> and
4939                   <span><strong class="command">recursive-clients</strong></span>
4940                   options instead.
4941                 </p></dd>
4942 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4943 <dd><p>
4944                   The maximum number of files the server
4945                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4946                 </p></dd>
4947 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4948 <dd><p>
4949                   The maximum amount of stack memory the server
4950                   may use. The default is <code class="literal">default</code>.
4951                 </p></dd>
4952 </dl></div>
4953 </div>
4954 <div class="sect3" lang="en">
4955 <div class="titlepage"><div><div><h4 class="title">
4956 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4957 <p>
4958             The following options set limits on the server's
4959             resource consumption that are enforced internally by the
4960             server rather than the operating system.
4961           </p>
4962 <div class="variablelist"><dl>
4963 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4964 <dd><p>
4965                   This option is obsolete; it is accepted
4966                   and ignored for BIND 8 compatibility.  The option
4967                   <span><strong class="command">max-journal-size</strong></span> performs a
4968                   similar function in BIND 9.
4969                 </p></dd>
4970 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4971 <dd><p>
4972                   Sets a maximum size for each journal file
4973                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4974                   approaches
4975                   the specified size, some of the oldest transactions in the
4976                   journal
4977                   will be automatically removed.  The largest permitted
4978                   value is 2 gigabytes. The default is
4979                   <code class="literal">unlimited</code>, which also
4980                   means 2 gigabytes.
4981                   This may also be set on a per-zone basis.
4982                 </p></dd>
4983 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4984 <dd><p>
4985                   In BIND 8, specifies the maximum number of host statistics
4986                   entries to be kept.
4987                   Not implemented in BIND 9.
4988                 </p></dd>
4989 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4990 <dd><p>
4991                   The maximum number of simultaneous recursive lookups
4992                   the server will perform on behalf of clients.  The default
4993                   is
4994                   <code class="literal">1000</code>.  Because each recursing
4995                   client uses a fair
4996                   bit of memory, on the order of 20 kilobytes, the value of
4997                   the
4998                   <span><strong class="command">recursive-clients</strong></span> option may
4999                   have to be decreased
5000                   on hosts with limited memory.
5001                 </p></dd>
5002 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
5003 <dd><p>
5004                   The maximum number of simultaneous client TCP
5005                   connections that the server will accept.
5006                   The default is <code class="literal">100</code>.
5007                 </p></dd>
5008 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
5009 <dd>
5010 <p>
5011                   The number of file descriptors reserved for TCP, stdio,
5012                   etc.  This needs to be big enough to cover the number of
5013                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
5014                   to provide room for outgoing TCP queries and incoming zone
5015                   transfers.  The default is <code class="literal">512</code>.
5016                   The minimum value is <code class="literal">128</code> and the
5017                   maximum value is <code class="literal">128</code> less than
5018                   maxsockets (-S).  This option may be removed in the future.
5019                 </p>
5020 <p>
5021                   This option has little effect on Windows.
5022                 </p>
5023 </dd>
5024 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
5025 <dd><p>
5026                   The maximum amount of memory to use for the
5027                   server's cache, in bytes.
5028                   When the amount of data in the cache
5029                   reaches this limit, the server will cause records to
5030                   expire prematurely based on an LRU based strategy so
5031                   that the limit is not exceeded.
5032                   The keyword <strong class="userinput"><code>unlimited</code></strong>,
5033                   or the value 0, will place no limit on cache size;
5034                   records will be purged from the cache only when their
5035                   TTLs expire.
5036                   Any positive values less than 2MB will be ignored
5037                   and reset to 2MB.
5038                   In a server with multiple views, the limit applies
5039                   separately to the cache of each view.
5040                   The default is <strong class="userinput"><code>unlimited</code></strong>.
5041                 </p></dd>
5042 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
5043 <dd><p>
5044                   The listen queue depth.  The default and minimum is 10.
5045                   If the kernel supports the accept filter "dataready" this
5046                   also controls how
5047                   many TCP connections that will be queued in kernel space
5048                   waiting for
5049                   some data before being passed to accept.  Nonzero values
5050                   less than 10 will be silently raised. A value of 0 may also
5051                   be used; on most platforms this sets the listen queue
5052                   length to a system-defined default value.
5053                 </p></dd>
5054 </dl></div>
5055 </div>
5056 <div class="sect3" lang="en">
5057 <div class="titlepage"><div><div><h4 class="title">
5058 <a name="id2586632"></a>Periodic Task Intervals</h4></div></div></div>
5059 <div class="variablelist"><dl>
5060 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
5061 <dd><p>
5062                   This interval is effectively obsolete.  Previously,
5063                   the server would remove expired resource records
5064                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
5065                   <acronym class="acronym">BIND</acronym> 9 now manages cache
5066                   memory in a more sophisticated manner and does not
5067                   rely on the periodic cleaning any more.
5068                   Specifying this option therefore has no effect on
5069                   the server's behavior.
5070                 </p></dd>
5071 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
5072 <dd><p>
5073                   The server will perform zone maintenance tasks
5074                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
5075                   interval expires. The default is 60 minutes. Reasonable
5076                   values are up
5077                   to 1 day (1440 minutes).  The maximum value is 28 days
5078                   (40320 minutes).
5079                   If set to 0, no zone maintenance for these zones will occur.
5080                 </p></dd>
5081 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
5082 <dd><p>
5083                   The server will scan the network interface list
5084                   every <span><strong class="command">interface-interval</strong></span>
5085                   minutes. The default
5086                   is 60 minutes. The maximum value is 28 days (40320 minutes).
5087                   If set to 0, interface scanning will only occur when
5088                   the configuration file is  loaded. After the scan, the
5089                   server will
5090                   begin listening for queries on any newly discovered
5091                   interfaces (provided they are allowed by the
5092                   <span><strong class="command">listen-on</strong></span> configuration), and
5093                   will
5094                   stop listening on interfaces that have gone away.
5095                 </p></dd>
5096 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
5097 <dd>
5098 <p>
5099                   Name server statistics will be logged
5100                   every <span><strong class="command">statistics-interval</strong></span>
5101                   minutes. The default is
5102                   60. The maximum value is 28 days (40320 minutes).
5103                   If set to 0, no statistics will be logged.
5104                   </p>
5105 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5106 <h3 class="title">Note</h3>
5107 <p>
5108                     Not yet implemented in
5109                     <acronym class="acronym">BIND</acronym> 9.
5110                   </p>
5111 </div>
5112 </dd>
5113 </dl></div>
5114 </div>
5115 <div class="sect3" lang="en">
5116 <div class="titlepage"><div><div><h4 class="title">
5117 <a name="topology"></a>Topology</h4></div></div></div>
5118 <p>
5119             All other things being equal, when the server chooses a name
5120             server
5121             to query from a list of name servers, it prefers the one that is
5122             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
5123             takes an <span><strong class="command">address_match_list</strong></span> and
5124             interprets it
5125             in a special way. Each top-level list element is assigned a
5126             distance.
5127             Non-negated elements get a distance based on their position in the
5128             list, where the closer the match is to the start of the list, the
5129             shorter the distance is between it and the server. A negated match
5130             will be assigned the maximum distance from the server. If there
5131             is no match, the address will get a distance which is further than
5132             any non-negated list element, and closer than any negated element.
5133             For example,
5134           </p>
5135 <pre class="programlisting">topology {
5136     10/8;
5137     !1.2.3/24;
5138     { 1.2/16; 3/8; };
5139 };</pre>
5140 <p>
5141             will prefer servers on network 10 the most, followed by hosts
5142             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
5143             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
5144             is preferred least of all.
5145           </p>
5146 <p>
5147             The default topology is
5148           </p>
5149 <pre class="programlisting">    topology { localhost; localnets; };
5150 </pre>
5151 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5152 <h3 class="title">Note</h3>
5153 <p>
5154               The <span><strong class="command">topology</strong></span> option
5155               is not implemented in <acronym class="acronym">BIND</acronym> 9.
5156             </p>
5157 </div>
5158 </div>
5159 <div class="sect3" lang="en">
5160 <div class="titlepage"><div><div><h4 class="title">
5161 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
5162 <p>
5163             The response to a DNS query may consist of multiple resource
5164             records (RRs) forming a resource records set (RRset).
5165             The name server will normally return the
5166             RRs within the RRset in an indeterminate order
5167             (but see the <span><strong class="command">rrset-order</strong></span>
5168             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
5169             The client resolver code should rearrange the RRs as appropriate,
5170             that is, using any addresses on the local net in preference to
5171             other addresses.
5172             However, not all resolvers can do this or are correctly
5173             configured.
5174             When a client is using a local server, the sorting can be performed
5175             in the server, based on the client's address. This only requires
5176             configuring the name servers, not all the clients.
5177           </p>
5178 <p>
5179             The <span><strong class="command">sortlist</strong></span> statement (see below)
5180             takes
5181             an <span><strong class="command">address_match_list</strong></span> and
5182             interprets it even
5183             more specifically than the <span><strong class="command">topology</strong></span>
5184             statement
5185             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
5186             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
5187             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
5188             one or two elements. The first element (which may be an IP
5189             address,
5190             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
5191             of each top level list is checked against the source address of
5192             the query until a match is found.
5193           </p>
5194 <p>
5195             Once the source address of the query has been matched, if
5196             the top level statement contains only one element, the actual
5197             primitive
5198             element that matched the source address is used to select the
5199             address
5200             in the response to move to the beginning of the response. If the
5201             statement is a list of two elements, then the second element is
5202             treated the same as the <span><strong class="command">address_match_list</strong></span> in
5203             a <span><strong class="command">topology</strong></span> statement. Each top
5204             level element
5205             is assigned a distance and the address in the response with the
5206             minimum
5207             distance is moved to the beginning of the response.
5208           </p>
5209 <p>
5210             In the following example, any queries received from any of
5211             the addresses of the host itself will get responses preferring
5212             addresses
5213             on any of the locally connected networks. Next most preferred are
5214             addresses
5215             on the 192.168.1/24 network, and after that either the
5216             192.168.2/24
5217             or
5218             192.168.3/24 network with no preference shown between these two
5219             networks. Queries received from a host on the 192.168.1/24 network
5220             will prefer other addresses on that network to the 192.168.2/24
5221             and
5222             192.168.3/24 networks. Queries received from a host on the
5223             192.168.4/24
5224             or the 192.168.5/24 network will only prefer other addresses on
5225             their directly connected networks.
5226           </p>
5227 <pre class="programlisting">sortlist {
5228     // IF the local host
5229     // THEN first fit on the following nets
5230     { localhost;
5231         { localnets;
5232             192.168.1/24;
5233             { 192.168.2/24; 192.168.3/24; }; }; };
5234     // IF on class C 192.168.1 THEN use .1, or .2 or .3
5235     { 192.168.1/24;
5236         { 192.168.1/24;
5237             { 192.168.2/24; 192.168.3/24; }; }; };
5238     // IF on class C 192.168.2 THEN use .2, or .1 or .3
5239     { 192.168.2/24;
5240         { 192.168.2/24;
5241             { 192.168.1/24; 192.168.3/24; }; }; };
5242     // IF on class C 192.168.3 THEN use .3, or .1 or .2
5243     { 192.168.3/24;
5244         { 192.168.3/24;
5245             { 192.168.1/24; 192.168.2/24; }; }; };
5246     // IF .4 or .5 THEN prefer that net
5247     { { 192.168.4/24; 192.168.5/24; };
5248     };
5249 };</pre>
5250 <p>
5251             The following example will give reasonable behavior for the
5252             local host and hosts on directly connected networks. It is similar
5253             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
5254             to queries from the local host will favor any of the directly
5255             connected
5256             networks. Responses sent to queries from any other hosts on a
5257             directly
5258             connected network will prefer addresses on that same network.
5259             Responses
5260             to other queries will not be sorted.
5261           </p>
5262 <pre class="programlisting">sortlist {
5263            { localhost; localnets; };
5264            { localnets; };
5265 };
5266 </pre>
5267 </div>
5268 <div class="sect3" lang="en">
5269 <div class="titlepage"><div><div><h4 class="title">
5270 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
5271 <p>
5272             When multiple records are returned in an answer it may be
5273             useful to configure the order of the records placed into the
5274             response.
5275             The <span><strong class="command">rrset-order</strong></span> statement permits
5276             configuration
5277             of the ordering of the records in a multiple record response.
5278             See also the <span><strong class="command">sortlist</strong></span> statement,
5279             <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a>.
5280           </p>
5281 <p>
5282             An <span><strong class="command">order_spec</strong></span> is defined as
5283             follows:
5284           </p>
5285 <p>
5286             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
5287             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
5288             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
5289             order <em class="replaceable"><code>ordering</code></em>
5290           </p>
5291 <p>
5292             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
5293             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
5294             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
5295           </p>
5296 <p>
5297             The legal values for <span><strong class="command">ordering</strong></span> are:
5298           </p>
5299 <div class="informaltable"><table border="1">
5300 <colgroup>
5301 <col>
5302 <col>
5303 </colgroup>
5304 <tbody>
5305 <tr>
5306 <td>
5307                     <p><span><strong class="command">fixed</strong></span></p>
5308                   </td>
5309 <td>
5310                     <p>
5311                       Records are returned in the order they
5312                       are defined in the zone file.
5313                     </p>
5314                   </td>
5315 </tr>
5316 <tr>
5317 <td>
5318                     <p><span><strong class="command">random</strong></span></p>
5319                   </td>
5320 <td>
5321                     <p>
5322                       Records are returned in some random order.
5323                     </p>
5324                   </td>
5325 </tr>
5326 <tr>
5327 <td>
5328                     <p><span><strong class="command">cyclic</strong></span></p>
5329                   </td>
5330 <td>
5331                     <p>
5332                       Records are returned in a cyclic round-robin order.
5333                     </p>
5334                     <p>
5335                       If <acronym class="acronym">BIND</acronym> is configured with the
5336                       "--enable-fixed-rrset" option at compile time, then
5337                       the initial ordering of the RRset will match the
5338                       one specified in the zone file.
5339                     </p>
5340                   </td>
5341 </tr>
5342 </tbody>
5343 </table></div>
5344 <p>
5345             For example:
5346           </p>
5347 <pre class="programlisting">rrset-order {
5348    class IN type A name "host.example.com" order random;
5349    order cyclic;
5350 };
5351 </pre>
5352 <p>
5353             will cause any responses for type A records in class IN that
5354             have "<code class="literal">host.example.com</code>" as a
5355             suffix, to always be returned
5356             in random order. All other records are returned in cyclic order.
5357           </p>
5358 <p>
5359             If multiple <span><strong class="command">rrset-order</strong></span> statements
5360             appear, they are not combined &#8212; the last one applies.
5361           </p>
5362 <p>
5363             By default, all records are returned in random order.
5364           </p>
5365 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5366 <h3 class="title">Note</h3>
5367 <p>
5368               In this release of <acronym class="acronym">BIND</acronym> 9, the
5369               <span><strong class="command">rrset-order</strong></span> statement does not support
5370               "fixed" ordering by default.  Fixed ordering can be enabled
5371               at compile time by specifying "--enable-fixed-rrset" on
5372               the "configure" command line.
5373             </p>
5374 </div>
5375 </div>
5376 <div class="sect3" lang="en">
5377 <div class="titlepage"><div><div><h4 class="title">
5378 <a name="tuning"></a>Tuning</h4></div></div></div>
5379 <div class="variablelist"><dl>
5380 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
5381 <dd>
5382 <p>
5383                   Sets the number of seconds to cache a
5384                   lame server indication. 0 disables caching. (This is
5385                   <span class="bold"><strong>NOT</strong></span> recommended.)
5386                   The default is <code class="literal">600</code> (10 minutes) and the
5387                   maximum value is
5388                   <code class="literal">1800</code> (30 minutes).
5389                 </p>
5390 <p>
5391                   Lame-ttl also controls the amount of time DNSSEC
5392                   validation failures are cached.  There is a minimum
5393                   of 30 seconds applied to bad cache entries if the
5394                   lame-ttl is set to less than 30 seconds.
5395                 </p>
5396 </dd>
5397 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
5398 <dd><p>
5399                   To reduce network traffic and increase performance,
5400                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
5401                   used to set a maximum retention time for these answers in
5402                   the server
5403                   in seconds. The default
5404                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
5405                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
5406                   7 days and will
5407                   be silently truncated to 7 days if set to a greater value.
5408                 </p></dd>
5409 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
5410 <dd><p>
5411                   Sets the maximum time for which the server will
5412                   cache ordinary (positive) answers. The default is
5413                   one week (7 days).
5414                   A value of zero may cause all queries to return
5415                   SERVFAIL, because of lost caches of intermediate
5416                   RRsets (such as NS and glue AAAA/A records) in the
5417                   resolution process.
5418                 </p></dd>
5419 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
5420 <dd>
5421 <p>
5422                   The minimum number of root servers that
5423                   is required for a request for the root servers to be
5424                   accepted. The default
5425                   is <strong class="userinput"><code>2</code></strong>.
5426                 </p>
5427 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5428 <h3 class="title">Note</h3>
5429 <p>
5430                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
5431                   </p>
5432 </div>
5433 </dd>
5434 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5435 <dd>
5436 <p>
5437                   Specifies the number of days into the future when
5438                   DNSSEC signatures automatically generated as a
5439                   result of dynamic updates (<a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>) will expire.  There
5440                   is an optional second field which specifies how
5441                   long before expiry that the signatures will be
5442                   regenerated.  If not specified, the signatures will
5443                   be regenerated at 1/4 of base interval.  The second
5444                   field is specified in days if the base interval is
5445                   greater than 7 days otherwise it is specified in hours.
5446                   The default base interval is <code class="literal">30</code> days
5447                   giving a re-signing interval of 7 1/2 days.  The maximum
5448                   values are 10 years (3660 days).
5449                 </p>
5450 <p>
5451                   The signature inception time is unconditionally
5452                   set to one hour before the current time to allow
5453                   for a limited amount of clock skew.
5454                 </p>
5455 <p>
5456                   The <span><strong class="command">sig-validity-interval</strong></span>
5457                   should be, at least, several multiples of the SOA
5458                   expire interval to allow for reasonable interaction
5459                   between the various timer and expiry dates.
5460                 </p>
5461 </dd>
5462 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
5463 <dd><p>
5464                   Specify the maximum number of nodes to be
5465                   examined in each quantum when signing a zone with
5466                   a new DNSKEY. The default is
5467                   <code class="literal">100</code>.
5468                 </p></dd>
5469 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
5470 <dd><p>
5471                   Specify a threshold number of signatures that
5472                   will terminate processing a quantum when signing
5473                   a zone with a new DNSKEY.  The default is
5474                   <code class="literal">10</code>.
5475                 </p></dd>
5476 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5477 <dd>
5478 <p>
5479                   Specify a private RDATA type to be used when generating
5480                   signing state records.  The default is
5481                   <code class="literal">65534</code>.
5482                 </p>
5483 <p>
5484                   It is expected that this parameter may be removed
5485                   in a future version once there is a standard type.
5486                 </p>
5487 <p>
5488                   Signing state records are used to internally by
5489                   <span><strong class="command">named</strong></span> to track the current state of
5490                   a zone-signing process, i.e., whether it is still active
5491                   or has been completed.  The records can be inspected
5492                   using the command
5493                   <span><strong class="command">rndc signing -list <em class="replaceable"><code>zone</code></em></strong></span>.
5494                   Once <span><strong class="command">named</strong></span> has finished signing
5495                   a zone with a particular key, the signing state
5496                   record associated with that key can be removed from
5497                   the zone by running
5498                   <span><strong class="command">rndc signing -clear <em class="replaceable"><code>keyid/algorithm</code></em> <em class="replaceable"><code>zone</code></em></strong></span>.
5499                   To clear all of the completed signing state
5500                   records for a zone, use
5501                   <span><strong class="command">rndc signing -clear all <em class="replaceable"><code>zone</code></em></strong></span>.
5502                 </p>
5503 </dd>
5504 <dt>
5505 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
5506 </dt>
5507 <dd>
5508 <p>
5509                   These options control the server's behavior on refreshing a
5510                   zone
5511                   (querying for SOA changes) or retrying failed transfers.
5512                   Usually the SOA values for the zone are used, but these
5513                   values
5514                   are set by the master, giving slave server administrators
5515                   little
5516                   control over their contents.
5517                 </p>
5518 <p>
5519                   These options allow the administrator to set a minimum and
5520                   maximum
5521                   refresh and retry time either per-zone, per-view, or
5522                   globally.
5523                   These options are valid for slave and stub zones,
5524                   and clamp the SOA refresh and retry times to the specified
5525                   values.
5526                 </p>
5527 <p>
5528                   The following defaults apply.
5529                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
5530                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
5531                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
5532                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
5533                   (2 weeks).
5534                 </p>
5535 </dd>
5536 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
5537 <dd>
5538 <p>
5539                   Sets the maximum advertised EDNS UDP buffer size in
5540                   bytes, to control the size of packets received from
5541                   authoritative servers in response to recursive queries.
5542                   Valid values are 512 to 4096 (values outside this range
5543                   will be silently adjusted to the nearest value within
5544                   it).  The default value is 4096.
5545                 </p>
5546 <p>
5547                   The usual reason for setting
5548                   <span><strong class="command">edns-udp-size</strong></span> to a non-default value
5549                   is to get UDP answers to pass through broken firewalls
5550                   that block fragmented packets and/or block UDP DNS
5551                   packets that are greater than 512 bytes.
5552                 </p>
5553 <p>
5554                   When <span><strong class="command">named</strong></span> first queries a remote
5555                   server, it will advertise a UDP buffer size of 512, as
5556                   this has the greatest chance of success on the first try.
5557                 </p>
5558 <p>
5559                   If the initial response times out, <span><strong class="command">named</strong></span>
5560                   will try again with plain DNS, and if that is successful,
5561                   it will be taken as evidence that the server does not
5562                   support EDNS. After enough failures using EDNS and
5563                   successes using plain DNS, <span><strong class="command">named</strong></span>
5564                   will default to plain DNS for future communications
5565                   with that server.  (Periodically, <span><strong class="command">named</strong></span>
5566                   will send an EDNS query to see if the situation has
5567                   improved.)
5568                 </p>
5569 <p>
5570                   However, if the initial query is successful with
5571                   EDNS advertising a buffer size of 512, then
5572                   <span><strong class="command">named</strong></span> will advertise progressively
5573                   larger buffer sizes on successive queries, until
5574                   responses begin timing out or
5575                   <span><strong class="command">edns-udp-size</strong></span> is reached.
5576                 </p>
5577 <p>
5578                   The default buffer sizes used by <span><strong class="command">named</strong></span>
5579                   are 512, 1232, 1432, and 4096, but never exceeding
5580                   <span><strong class="command">edns-udp-size</strong></span>.  (The values 1232 and
5581                   1432 are chosen to allow for an IPv4/IPv6 encapsulated
5582                   UDP message to be sent without fragmentation at the
5583                   minimum MTU sizes for Ethernet and IPv6 networks.)
5584                 </p>
5585 </dd>
5586 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
5587 <dd>
5588 <p>
5589                   Sets the maximum EDNS UDP message size
5590                   <span><strong class="command">named</strong></span> will send in bytes.
5591                   Valid values are 512 to 4096 (values outside this
5592                   range will be silently adjusted to the nearest
5593                   value within it).  The default value is 4096.
5594                 </p>
5595 <p>
5596                   This value applies to responses sent by a server; to
5597                   set the advertised buffer size in queries, see
5598                   <span><strong class="command">edns-udp-size</strong></span>.
5599                 </p>
5600 <p>
5601                   The usual reason for setting
5602                   <span><strong class="command">max-udp-size</strong></span> to a non-default
5603                   value is to get UDP answers to pass through broken
5604                   firewalls that block fragmented packets and/or
5605                   block UDP packets that are greater than 512 bytes.
5606                   This is independent of the advertised receive
5607                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
5608                 </p>
5609 <p>
5610                   Setting this to a low value will encourage additional
5611                   TCP traffic to the nameserver.
5612                 </p>
5613 </dd>
5614 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5615 <dd>
5616 <p>Specifies
5617                   the file format of zone files (see
5618                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5619                   The default value is <code class="constant">text</code>, which is the
5620                   standard textual representation, except for slave zones,
5621                   in which the default value is <code class="constant">raw</code>.
5622                   Files in other formats than <code class="constant">text</code> are
5623                   typically expected to be generated by the
5624                   <span><strong class="command">named-compilezone</strong></span> tool, or dumped by
5625                   <span><strong class="command">named</strong></span>.
5626                 </p>
5627 <p>
5628                   Note that when a zone file in a different format than
5629                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
5630                   may omit some of the checks which would be performed for a
5631                   file in the <code class="constant">text</code> format.  In particular,
5632                   <span><strong class="command">check-names</strong></span> checks do not apply
5633                   for the <code class="constant">raw</code> format.  This means
5634                   a zone file in the <code class="constant">raw</code> format
5635                   must be generated with the same check level as that
5636                   specified in the <span><strong class="command">named</strong></span> configuration
5637                   file.  Also, <code class="constant">map</code> format files are
5638                   loaded directly into memory via memory mapping, with only
5639                   minimal checking.
5640                 </p>
5641 <p>
5642                   This statement sets the
5643                   <span><strong class="command">masterfile-format</strong></span> for all zones,
5644                   but can be overridden on a per-zone or per-view basis
5645                   by including a <span><strong class="command">masterfile-format</strong></span>
5646                   statement within the <span><strong class="command">zone</strong></span> or
5647                   <span><strong class="command">view</strong></span> block in the configuration
5648                   file.
5649                 </p>
5650 </dd>
5651 <dt>
5652 <a name="clients-per-query"></a><span class="term"><span><strong class="command">clients-per-query</strong></span>, </span><span class="term"><span><strong class="command">max-clients-per-query</strong></span></span>
5653 </dt>
5654 <dd>
5655 <p>These set the
5656                   initial value (minimum) and maximum number of recursive
5657                   simultaneous clients for any given query
5658                   (&lt;qname,qtype,qclass&gt;) that the server will accept
5659                   before dropping additional clients.
5660                   <span><strong class="command">named</strong></span> will attempt to
5661                   self tune this value and changes will be logged.  The
5662                   default values are 10 and 100.
5663                 </p>
5664 <p>
5665                   This value should reflect how many queries come in for
5666                   a given name in the time it takes to resolve that name.
5667                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
5668                   assume that it is dealing with a non-responsive zone
5669                   and will drop additional queries.  If it gets a response
5670                   after dropping queries, it will raise the estimate.  The
5671                   estimate will then be lowered in 20 minutes if it has
5672                   remained unchanged.
5673                 </p>
5674 <p>
5675                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
5676                   then there is no limit on the number of clients per query
5677                   and no queries will be dropped.
5678                 </p>
5679 <p>
5680                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
5681                   then there is no upper bound other than imposed by
5682                   <span><strong class="command">recursive-clients</strong></span>.
5683                 </p>
5684 </dd>
5685 <dt>
5686 <a name="max-recursion-depth"></a><span class="term"><span><strong class="command">max-recursion-depth</strong></span></span>
5687 </dt>
5688 <dd><p>
5689                   Sets the maximum number of levels of recursion
5690                   that are permitted at any one time while servicing
5691                   a recursive query. Resolving a name may require
5692                   looking up a name server address, which in turn
5693                   requires resolving another name, etc; if the number
5694                   of indirections exceeds this value, the recursive
5695                   query is terminated and returns SERVFAIL.  The
5696                   default is 7.
5697                 </p></dd>
5698 <dt>
5699 <a name="max-recursion-queries"></a><span class="term"><span><strong class="command">max-recursion-queries</strong></span></span>
5700 </dt>
5701 <dd><p>
5702                   Sets the maximum number of iterative queries that
5703                   may be sent while servicing a recursive query.
5704                   If more queries are sent, the recursive query
5705                   is terminated and returns SERVFAIL. Queries to
5706                   look up top level comains such as "com" and "net"
5707                   and the DNS root zone are exempt from this limitation.
5708                   The default is 75.
5709                 </p></dd>
5710 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5711 <dd>
5712 <p>
5713                   The delay, in seconds, between sending sets of notify
5714                   messages for a zone.  The default is five (5) seconds.
5715                 </p>
5716 <p>
5717                   The overall rate that NOTIFY messages are sent for all
5718                   zones is controlled by <span><strong class="command">serial-query-rate</strong></span>.
5719                 </p>
5720 </dd>
5721 <dt><span class="term"><span><strong class="command">max-rsa-exponent-size</strong></span></span></dt>
5722 <dd><p>
5723                   The maximum RSA exponent size, in bits, that will
5724                   be accepted when validating.  Valid values are 35
5725                   to 4096 bits.  The default zero (0) is also accepted
5726                   and is equivalent to 4096.
5727                 </p></dd>
5728 <dt><span class="term"><span><strong class="command">prefetch</strong></span></span></dt>
5729 <dd>
5730 <p>
5731                   When a query is received for cached data which
5732                   is to expire shortly, <span><strong class="command">named</strong></span> can
5733                   refresh the data from the authoritative server
5734                   immediately, ensuring that the cache always has an
5735                   answer available.
5736                 </p>
5737 <p>
5738                   The <code class="option">prefetch</code> specifies the
5739                   "trigger" TTL value at which prefetch of the current
5740                   query will take place: when a cache record with a
5741                   lower TTL value is encountered during query processing,
5742                   it will be refreshed.  Valid trigger TTL values are 1 to
5743                   10 seconds.  Values larger than 10 seconds will be silently
5744                   reduced to 10.
5745                   Setting a trigger TTL to zero (0) causes
5746                   prefetch to be disabled.
5747                   The default trigger TTL is <code class="literal">2</code>.
5748                 </p>
5749 <p>
5750                   An optional second argument specifies the "eligibility"
5751                   TTL: the smallest <span class="emphasis"><em>original</em></span>
5752                   TTL value that will be accepted for a record to be
5753                   eligible for prefetching.  The eligibility TTL must
5754                   be at least six seconds longer than the trigger TTL;
5755                   if it isn't, <span><strong class="command">named</strong></span> will silently
5756                   adjust it upward.
5757                   The default eligibility TTL is <code class="literal">9</code>.
5758                 </p>
5759 </dd>
5760 </dl></div>
5761 </div>
5762 <div class="sect3" lang="en">
5763 <div class="titlepage"><div><div><h4 class="title">
5764 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5765 <p>
5766             The server provides some helpful diagnostic information
5767             through a number of built-in zones under the
5768             pseudo-top-level-domain <code class="literal">bind</code> in the
5769             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
5770             of a
5771             built-in view (see <a href="Bv9ARM.ch06.html#view_statement_grammar" title="view Statement Grammar">the section called &#8220;<span><strong class="command">view</strong></span> Statement Grammar&#8221;</a>) of
5772             class
5773             <span><strong class="command">CHAOS</strong></span> which is separate from the
5774             default view of class <span><strong class="command">IN</strong></span>. Most global
5775             configuration options (<span><strong class="command">allow-query</strong></span>,
5776             etc) will apply to this view, but some are locally
5777             overridden: <span><strong class="command">notify</strong></span>,
5778             <span><strong class="command">recursion</strong></span> and
5779             <span><strong class="command">allow-new-zones</strong></span> are
5780             always set to <strong class="userinput"><code>no</code></strong>, and
5781             <span><strong class="command">rate-limit</strong></span> is set to allow
5782             three responses per second.
5783           </p>
5784 <p>
5785             If you need to disable these zones, use the options
5786             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5787             view by
5788             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5789             that matches all clients.
5790           </p>
5791 <div class="variablelist"><dl>
5792 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5793 <dd><p>
5794                   The version the server should report
5795                   via a query of the name <code class="literal">version.bind</code>
5796                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5797                   The default is the real version number of this server.
5798                   Specifying <span><strong class="command">version none</strong></span>
5799                   disables processing of the queries.
5800                 </p></dd>
5801 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5802 <dd><p>
5803                   The hostname the server should report via a query of
5804                   the name <code class="filename">hostname.bind</code>
5805                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5806                   This defaults to the hostname of the machine hosting the
5807                   name server as
5808                   found by the gethostname() function.  The primary purpose of such queries
5809                   is to
5810                   identify which of a group of anycast servers is actually
5811                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5812                   disables processing of the queries.
5813                 </p></dd>
5814 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5815 <dd><p>
5816                   The ID the server should report when receiving a Name
5817                   Server Identifier (NSID) query, or a query of the name
5818                   <code class="filename">ID.SERVER</code> with type
5819                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5820                   The primary purpose of such queries is to
5821                   identify which of a group of anycast servers is actually
5822                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5823                   disables processing of the queries.
5824                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5825                   use the hostname as found by the gethostname() function.
5826                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5827                 </p></dd>
5828 </dl></div>
5829 </div>
5830 <div class="sect3" lang="en">
5831 <div class="titlepage"><div><div><h4 class="title">
5832 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5833 <p>
5834             Named has some built-in empty zones (SOA and NS records only).
5835             These are for zones that should normally be answered locally
5836             and which queries should not be sent to the Internet's root
5837             servers.  The official servers which cover these namespaces
5838             return NXDOMAIN responses to these queries.  In particular,
5839             these cover the reverse namespaces for addresses from
5840             RFC 1918, RFC 4193, RFC 5737 and RFC 6598.  They also include the
5841             reverse namespace for IPv6 local address (locally assigned),
5842             IPv6 link local addresses, the IPv6 loopback address and the
5843             IPv6 unknown address.
5844           </p>
5845 <p>
5846             Named will attempt to determine if a built-in zone already exists
5847             or is active (covered by a forward-only forwarding declaration)
5848             and will not create an empty zone in that case.
5849           </p>
5850 <p>
5851             The current list of empty zones is:
5852             </p>
5853 <div class="itemizedlist"><ul type="disc">
5854 <li>10.IN-ADDR.ARPA</li>
5855 <li>16.172.IN-ADDR.ARPA</li>
5856 <li>17.172.IN-ADDR.ARPA</li>
5857 <li>18.172.IN-ADDR.ARPA</li>
5858 <li>19.172.IN-ADDR.ARPA</li>
5859 <li>20.172.IN-ADDR.ARPA</li>
5860 <li>21.172.IN-ADDR.ARPA</li>
5861 <li>22.172.IN-ADDR.ARPA</li>
5862 <li>23.172.IN-ADDR.ARPA</li>
5863 <li>24.172.IN-ADDR.ARPA</li>
5864 <li>25.172.IN-ADDR.ARPA</li>
5865 <li>26.172.IN-ADDR.ARPA</li>
5866 <li>27.172.IN-ADDR.ARPA</li>
5867 <li>28.172.IN-ADDR.ARPA</li>
5868 <li>29.172.IN-ADDR.ARPA</li>
5869 <li>30.172.IN-ADDR.ARPA</li>
5870 <li>31.172.IN-ADDR.ARPA</li>
5871 <li>168.192.IN-ADDR.ARPA</li>
5872 <li>64.100.IN-ADDR.ARPA</li>
5873 <li>65.100.IN-ADDR.ARPA</li>
5874 <li>66.100.IN-ADDR.ARPA</li>
5875 <li>67.100.IN-ADDR.ARPA</li>
5876 <li>68.100.IN-ADDR.ARPA</li>
5877 <li>69.100.IN-ADDR.ARPA</li>
5878 <li>70.100.IN-ADDR.ARPA</li>
5879 <li>71.100.IN-ADDR.ARPA</li>
5880 <li>72.100.IN-ADDR.ARPA</li>
5881 <li>73.100.IN-ADDR.ARPA</li>
5882 <li>74.100.IN-ADDR.ARPA</li>
5883 <li>75.100.IN-ADDR.ARPA</li>
5884 <li>76.100.IN-ADDR.ARPA</li>
5885 <li>77.100.IN-ADDR.ARPA</li>
5886 <li>78.100.IN-ADDR.ARPA</li>
5887 <li>79.100.IN-ADDR.ARPA</li>
5888 <li>80.100.IN-ADDR.ARPA</li>
5889 <li>81.100.IN-ADDR.ARPA</li>
5890 <li>82.100.IN-ADDR.ARPA</li>
5891 <li>83.100.IN-ADDR.ARPA</li>
5892 <li>84.100.IN-ADDR.ARPA</li>
5893 <li>85.100.IN-ADDR.ARPA</li>
5894 <li>86.100.IN-ADDR.ARPA</li>
5895 <li>87.100.IN-ADDR.ARPA</li>
5896 <li>88.100.IN-ADDR.ARPA</li>
5897 <li>89.100.IN-ADDR.ARPA</li>
5898 <li>90.100.IN-ADDR.ARPA</li>
5899 <li>91.100.IN-ADDR.ARPA</li>
5900 <li>92.100.IN-ADDR.ARPA</li>
5901 <li>93.100.IN-ADDR.ARPA</li>
5902 <li>94.100.IN-ADDR.ARPA</li>
5903 <li>95.100.IN-ADDR.ARPA</li>
5904 <li>96.100.IN-ADDR.ARPA</li>
5905 <li>97.100.IN-ADDR.ARPA</li>
5906 <li>98.100.IN-ADDR.ARPA</li>
5907 <li>99.100.IN-ADDR.ARPA</li>
5908 <li>100.100.IN-ADDR.ARPA</li>
5909 <li>101.100.IN-ADDR.ARPA</li>
5910 <li>102.100.IN-ADDR.ARPA</li>
5911 <li>103.100.IN-ADDR.ARPA</li>
5912 <li>104.100.IN-ADDR.ARPA</li>
5913 <li>105.100.IN-ADDR.ARPA</li>
5914 <li>106.100.IN-ADDR.ARPA</li>
5915 <li>107.100.IN-ADDR.ARPA</li>
5916 <li>108.100.IN-ADDR.ARPA</li>
5917 <li>109.100.IN-ADDR.ARPA</li>
5918 <li>110.100.IN-ADDR.ARPA</li>
5919 <li>111.100.IN-ADDR.ARPA</li>
5920 <li>112.100.IN-ADDR.ARPA</li>
5921 <li>113.100.IN-ADDR.ARPA</li>
5922 <li>114.100.IN-ADDR.ARPA</li>
5923 <li>115.100.IN-ADDR.ARPA</li>
5924 <li>116.100.IN-ADDR.ARPA</li>
5925 <li>117.100.IN-ADDR.ARPA</li>
5926 <li>118.100.IN-ADDR.ARPA</li>
5927 <li>119.100.IN-ADDR.ARPA</li>
5928 <li>120.100.IN-ADDR.ARPA</li>
5929 <li>121.100.IN-ADDR.ARPA</li>
5930 <li>122.100.IN-ADDR.ARPA</li>
5931 <li>123.100.IN-ADDR.ARPA</li>
5932 <li>124.100.IN-ADDR.ARPA</li>
5933 <li>125.100.IN-ADDR.ARPA</li>
5934 <li>126.100.IN-ADDR.ARPA</li>
5935 <li>127.100.IN-ADDR.ARPA</li>
5936 <li>0.IN-ADDR.ARPA</li>
5937 <li>127.IN-ADDR.ARPA</li>
5938 <li>254.169.IN-ADDR.ARPA</li>
5939 <li>2.0.192.IN-ADDR.ARPA</li>
5940 <li>100.51.198.IN-ADDR.ARPA</li>
5941 <li>113.0.203.IN-ADDR.ARPA</li>
5942 <li>255.255.255.255.IN-ADDR.ARPA</li>
5943 <li>0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5944 <li>1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5945 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
5946 <li>D.F.IP6.ARPA</li>
5947 <li>8.E.F.IP6.ARPA</li>
5948 <li>9.E.F.IP6.ARPA</li>
5949 <li>A.E.F.IP6.ARPA</li>
5950 <li>B.E.F.IP6.ARPA</li>
5951 </ul></div>
5952 <p>
5953           </p>
5954 <p>
5955             Empty zones are settable at the view level and only apply to
5956             views of class IN.  Disabled empty zones are only inherited
5957             from options if there are no disabled empty zones specified
5958             at the view level.  To override the options list of disabled
5959             zones, you can disable the root zone at the view level, for example:
5960 </p>
5961 <pre class="programlisting">
5962             disable-empty-zone ".";
5963 </pre>
5964 <p>
5965           </p>
5966 <p>
5967             If you are using the address ranges covered here, you should
5968             already have reverse zones covering the addresses you use.
5969             In practice this appears to not be the case with many queries
5970             being made to the infrastructure servers for names in these
5971             spaces.  So many in fact that sacrificial servers were needed
5972             to be deployed to channel the query load away from the
5973             infrastructure servers.
5974           </p>
5975 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5976 <h3 class="title">Note</h3>
5977             The real parent servers for these zones should disable all
5978             empty zone under the parent zone they serve.  For the real
5979             root servers, this is all built-in empty zones.  This will
5980             enable them to return referrals to deeper in the tree.
5981           </div>
5982 <div class="variablelist"><dl>
5983 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5984 <dd><p>
5985                   Specify what server name will appear in the returned
5986                   SOA record for empty zones.  If none is specified, then
5987                   the zone's name will be used.
5988                 </p></dd>
5989 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5990 <dd><p>
5991                   Specify what contact name will appear in the returned
5992                   SOA record for empty zones.  If none is specified, then
5993                   "." will be used.
5994                 </p></dd>
5995 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5996 <dd><p>
5997                   Enable or disable all empty zones.  By default, they
5998                   are enabled.
5999                 </p></dd>
6000 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
6001 <dd><p>
6002                   Disable individual empty zones.  By default, none are
6003                   disabled.  This option can be specified multiple times.
6004                 </p></dd>
6005 </dl></div>
6006 </div>
6007 <div class="sect3" lang="en">
6008 <div class="titlepage"><div><div><h4 class="title">
6009 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
6010 <p>
6011             The additional section cache, also called <span><strong class="command">acache</strong></span>,
6012             is an internal cache to improve the response performance of BIND 9.
6013             When additional section caching is enabled, BIND 9 will
6014             cache an internal short-cut to the additional section content for
6015             each answer RR.
6016             Note that <span><strong class="command">acache</strong></span> is an internal caching
6017             mechanism of BIND 9, and is not related to the DNS caching
6018             server function.
6019           </p>
6020 <p>
6021             Additional section caching does not change the
6022             response content (except the RRsets ordering of the additional
6023             section, see below), but can improve the response performance
6024             significantly.
6025             It is particularly effective when BIND 9 acts as an authoritative
6026             server for a zone that has many delegations with many glue RRs.
6027           </p>
6028 <p>
6029             In order to obtain the maximum performance improvement
6030             from additional section caching, setting
6031             <span><strong class="command">additional-from-cache</strong></span>
6032             to <span><strong class="command">no</strong></span> is recommended, since the current
6033             implementation of <span><strong class="command">acache</strong></span>
6034             does not short-cut of additional section information from the
6035             DNS cache data.
6036           </p>
6037 <p>
6038             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
6039             that it requires much more
6040             memory for the internal cached data.
6041             Thus, if the response performance does not matter and memory
6042             consumption is much more critical, the
6043             <span><strong class="command">acache</strong></span> mechanism can be
6044             disabled by setting <span><strong class="command">acache-enable</strong></span> to
6045             <span><strong class="command">no</strong></span>.
6046             It is also possible to specify the upper limit of memory
6047             consumption
6048             for acache by using <span><strong class="command">max-acache-size</strong></span>.
6049           </p>
6050 <p>
6051             Additional section caching also has a minor effect on the
6052             RRset ordering in the additional section.
6053             Without <span><strong class="command">acache</strong></span>,
6054             <span><strong class="command">cyclic</strong></span> order is effective for the additional
6055             section as well as the answer and authority sections.
6056             However, additional section caching fixes the ordering when it
6057             first caches an RRset for the additional section, and the same
6058             ordering will be kept in succeeding responses, regardless of the
6059             setting of <span><strong class="command">rrset-order</strong></span>.
6060             The effect of this should be minor, however, since an
6061             RRset in the additional section
6062             typically only contains a small number of RRs (and in many cases
6063             it only contains a single RR), in which case the
6064             ordering does not matter much.
6065           </p>
6066 <p>
6067             The following is a summary of options related to
6068             <span><strong class="command">acache</strong></span>.
6069           </p>
6070 <div class="variablelist"><dl>
6071 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
6072 <dd><p>
6073                   If <span><strong class="command">yes</strong></span>, additional section caching is
6074                   enabled.  The default value is <span><strong class="command">no</strong></span>.
6075                 </p></dd>
6076 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
6077 <dd><p>
6078                   The server will remove stale cache entries, based on an LRU
6079                   based
6080                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
6081                   The default is 60 minutes.
6082                   If set to 0, no periodic cleaning will occur.
6083                 </p></dd>
6084 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
6085 <dd><p>
6086                   The maximum amount of memory in bytes to use for the server's acache.
6087                   When the amount of data in the acache reaches this limit,
6088                   the server
6089                   will clean more aggressively so that the limit is not
6090                   exceeded.
6091                   In a server with multiple views, the limit applies
6092                   separately to the
6093                   acache of each view.
6094                   The default is <code class="literal">16M</code>.
6095                 </p></dd>
6096 </dl></div>
6097 </div>
6098 <div class="sect3" lang="en">
6099 <div class="titlepage"><div><div><h4 class="title">
6100 <a name="id2589422"></a>Content Filtering</h4></div></div></div>
6101 <p>
6102             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
6103             out DNS responses from external DNS servers containing
6104             certain types of data in the answer section.
6105             Specifically, it can reject address (A or AAAA) records if
6106             the corresponding IPv4 or IPv6 addresses match the given
6107             <code class="varname">address_match_list</code> of the
6108             <span><strong class="command">deny-answer-addresses</strong></span> option.
6109             It can also reject CNAME or DNAME records if the "alias"
6110             name (i.e., the CNAME alias or the substituted query name
6111             due to DNAME) matches the
6112             given <code class="varname">namelist</code> of the
6113             <span><strong class="command">deny-answer-aliases</strong></span> option, where
6114             "match" means the alias name is a subdomain of one of
6115             the <code class="varname">name_list</code> elements.
6116             If the optional <code class="varname">namelist</code> is specified
6117             with <span><strong class="command">except-from</strong></span>, records whose query name
6118             matches the list will be accepted regardless of the filter
6119             setting.
6120             Likewise, if the alias name is a subdomain of the
6121             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
6122             filter will not apply;
6123             for example, even if "example.com" is specified for
6124             <span><strong class="command">deny-answer-aliases</strong></span>,
6125           </p>
6126 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
6127 <p>
6128             returned by an "example.com" server will be accepted.
6129           </p>
6130 <p>
6131             In the <code class="varname">address_match_list</code> of the
6132             <span><strong class="command">deny-answer-addresses</strong></span> option, only
6133             <code class="varname">ip_addr</code>
6134             and <code class="varname">ip_prefix</code>
6135             are meaningful;
6136             any <code class="varname">key_id</code> will be silently ignored.
6137           </p>
6138 <p>
6139             If a response message is rejected due to the filtering,
6140             the entire message is discarded without being cached, and
6141             a SERVFAIL error will be returned to the client.
6142           </p>
6143 <p>
6144             This filtering is intended to prevent "DNS rebinding attacks," in
6145             which an attacker, in response to a query for a domain name the
6146             attacker controls, returns an IP address within your own network or
6147             an alias name within your own domain.
6148             A naive web browser or script could then serve as an
6149             unintended proxy, allowing the attacker
6150             to get access to an internal node of your local network
6151             that couldn't be externally accessed otherwise.
6152             See the paper available at
6153             <a href="http://portal.acm.org/citation.cfm?id=1315245.1315298" target="_top">
6154             http://portal.acm.org/citation.cfm?id=1315245.1315298
6155             </a>
6156             for more details about the attacks.
6157           </p>
6158 <p>
6159             For example, if you own a domain named "example.net" and
6160             your internal network uses an IPv4 prefix 192.0.2.0/24,
6161             you might specify the following rules:
6162           </p>
6163 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
6164 deny-answer-aliases { "example.net"; };
6165 </pre>
6166 <p>
6167             If an external attacker lets a web browser in your local
6168             network look up an IPv4 address of "attacker.example.com",
6169             the attacker's DNS server would return a response like this:
6170           </p>
6171 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
6172 <p>
6173             in the answer section.
6174             Since the rdata of this record (the IPv4 address) matches
6175             the specified prefix 192.0.2.0/24, this response will be
6176             ignored.
6177           </p>
6178 <p>
6179             On the other hand, if the browser looks up a legitimate
6180             internal web server "www.example.net" and the
6181             following response is returned to
6182             the <acronym class="acronym">BIND</acronym> 9 server
6183           </p>
6184 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
6185 <p>
6186             it will be accepted since the owner name "www.example.net"
6187             matches the <span><strong class="command">except-from</strong></span> element,
6188             "example.net".
6189           </p>
6190 <p>
6191             Note that this is not really an attack on the DNS per se.
6192             In fact, there is nothing wrong for an "external" name to
6193             be mapped to your "internal" IP address or domain name
6194             from the DNS point of view.
6195             It might actually be provided for a legitimate purpose,
6196             such as for debugging.
6197             As long as the mapping is provided by the correct owner,
6198             it is not possible or does not make sense to detect
6199             whether the intent of the mapping is legitimate or not
6200             within the DNS.
6201             The "rebinding" attack must primarily be protected at the
6202             application that uses the DNS.
6203             For a large site, however, it may be difficult to protect
6204             all possible applications at once.
6205             This filtering feature is provided only to help such an
6206             operational environment;
6207             it is generally discouraged to turn it on unless you are
6208             very sure you have no other choice and the attack is a
6209             real threat for your applications.
6210           </p>
6211 <p>
6212             Care should be particularly taken if you want to use this
6213             option for addresses within 127.0.0.0/8.
6214             These addresses are obviously "internal", but many
6215             applications conventionally rely on a DNS mapping from
6216             some name to such an address.
6217             Filtering out DNS records containing this address
6218             spuriously can break such applications.
6219           </p>
6220 </div>
6221 <div class="sect3" lang="en">
6222 <div class="titlepage"><div><div><h4 class="title">
6223 <a name="id2589548"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
6224 <p>
6225             <acronym class="acronym">BIND</acronym> 9 includes a limited
6226             mechanism to modify DNS responses for requests
6227             analogous to email anti-spam DNS blacklists.
6228             Responses can be changed to deny the existence of domains (NXDOMAIN),
6229             deny the existence of IP addresses for domains (NODATA),
6230             or contain other IP addresses or data.
6231           </p>
6232 <p>
6233             Response policy zones are named in the
6234             <span><strong class="command">response-policy</strong></span> option for the view or among the
6235             global options if there is no response-policy option for the view.
6236             Response policy zones are ordinary DNS zones containing RRsets
6237             that can be queried normally if allowed.
6238             It is usually best to restrict those queries with something like
6239             <span><strong class="command">allow-query { localhost; };</strong></span>.
6240           </p>
6241 <p>
6242             A <span><strong class="command">response-policy</strong></span> option can support
6243             multiple policy zones.  To maximize performance, a radix
6244             tree is used to quickly identify response policy zones
6245             containing triggers that match the current query.  This
6246             imposes an upper limit of 32 on the number of policy zones
6247             in a single <span><strong class="command">response-policy</strong></span> option; more
6248             than that is a configuration error.
6249           </p>
6250 <p>
6251             Five policy triggers can be encoded in RPZ records.
6252             </p>
6253 <div class="variablelist"><dl>
6254 <dt><span class="term"><span><strong class="command">RPZ-CLIENT-IP</strong></span></span></dt>
6255 <dd>
6256 <p>
6257                     IP records are triggered by the IP address of the
6258                     DNS client.
6259                     Client IP address triggers are encoded in records that have
6260                     owner names that are subdomains of
6261                     <span><strong class="command">rpz-client-ip</strong></span> relativized to the
6262                     policy zone origin name
6263                     and encode an address or address block.
6264                     IPv4 addresses are represented as
6265                     <strong class="userinput"><code>prefixlength.B4.B3.B2.B1.rpz-ip</code></strong>.
6266                     The IPv4 prefix length must be between 1 and 32.
6267                     All four bytes, B4, B3, B2, and B1, must be present.
6268                     B4 is the decimal value of the least significant byte of the
6269                     IPv4 address as in IN-ADDR.ARPA.
6270                   </p>
6271 <p>
6272                     IPv6 addresses are encoded in a format similar
6273                     to the standard IPv6 text representation,
6274                     <strong class="userinput"><code>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</code></strong>.
6275                     Each of W8,...,W1 is a one to four digit hexadecimal number
6276                     representing 16 bits of the IPv6 address as in the standard
6277                     text representation of IPv6 addresses,
6278                     but reversed as in IN-ADDR.ARPA.
6279                     All 8 words must be present except when one set of consecutive
6280                     zero words is replaced with <strong class="userinput"><code>.zz.</code></strong>
6281                     analogous to double colons (::) in standard IPv6 text
6282                     encodings.
6283                     The IPv6 prefix length must be between 64 and 128.
6284                   </p>
6285 </dd>
6286 <dt><span class="term"><span><strong class="command">QNAME</strong></span></span></dt>
6287 <dd><p>
6288                     QNAME policy records are triggered by query names of
6289                     requests and targets of CNAME records resolved to generate
6290                     the response.
6291                     The owner name of a QNAME policy record is
6292                     the query name relativized to the policy zone.
6293                   </p></dd>
6294 <dt><span class="term"><span><strong class="command">RPZ-IP</strong></span></span></dt>
6295 <dd><p>
6296                     IP triggers are IP addresses in an
6297                     A or AAAA record in the ANSWER section of a response.
6298                     They are encoded like client-IP triggers except as
6299                     subdomains of <span><strong class="command">rpz-ip</strong></span>.
6300                   </p></dd>
6301 <dt><span class="term"><span><strong class="command">RPZ-NSDNAME</strong></span></span></dt>
6302 <dd><p>
6303                     NSDNAME triggers match names of authoritative servers
6304                     for the query name, a parent of the query name, a CNAME for
6305                     query name, or a parent of a CNAME.
6306                     They are encoded as subdomains of
6307                     <span><strong class="command">rpz-nsdname</strong></span> relativized
6308                     to the RPZ origin name.
6309                     NSIP triggers match IP addresses in A and
6310                     AAAA RRsets for domains that can be checked against NSDNAME
6311                     policy records.
6312                   </p></dd>
6313 <dt><span class="term"><span><strong class="command">RPZ-NSIP</strong></span></span></dt>
6314 <dd><p>
6315                     NSIP triggers are encoded like IP triggers except as
6316                     subdomains of <span><strong class="command">rpz-nsip</strong></span>.
6317                     NSDNAME and NSIP triggers are checked only for names with at
6318                     least <span><strong class="command">min-ns-dots</strong></span> dots.
6319                     The default value of <span><strong class="command">min-ns-dots</strong></span> is 1 to
6320                     exclude top level domains.
6321                   </p></dd>
6322 </dl></div>
6323 <p>
6324           </p>
6325 <p>
6326             The query response is checked against all response policy zones,
6327             so two or more policy records can be triggered by a response.
6328             Because DNS responses are rewritten according to at most one
6329             policy record, a single record encoding an action (other than
6330             <span><strong class="command">DISABLED</strong></span> actions) must be chosen.
6331             Triggers or the records that encode them are chosen for the
6332             rewriting in the following order:
6333             </p>
6334 <div class="orderedlist"><ol type="1">
6335 <li>Choose the triggered record in the zone that appears
6336                 first in the <span><strong class="command">response-policy</strong></span> option.
6337               </li>
6338 <li>Prefer CLIENT-IP to QNAME to IP to NSDNAME to NSIP
6339                 triggers in a single zone.
6340               </li>
6341 <li>Among NSDNAME triggers, prefer the
6342                 trigger that matches the smallest name under the DNSSEC ordering.
6343               </li>
6344 <li>Among IP or NSIP triggers, prefer the trigger
6345                 with the longest prefix.
6346               </li>
6347 <li>Among triggers with the same prefix length,
6348                 prefer the IP or NSIP trigger that matches
6349                 the smallest IP address.
6350               </li>
6351 </ol></div>
6352 <p>
6353           </p>
6354 <p>
6355             When the processing of a response is restarted to resolve
6356             DNAME or CNAME records and a policy record set has
6357             not been triggered,
6358             all response policy zones are again consulted for the
6359             DNAME or CNAME names and addresses.
6360           </p>
6361 <p>
6362             RPZ record sets are any types of DNS record except
6363             DNAME or DNSSEC that encode actions or responses to
6364             individual queries.
6365             Any of the policies can be used with any of the triggers.
6366             For example, while the <span><strong class="command">TCP-only</strong></span> policy is
6367             commonly used with <span><strong class="command">client-IP</strong></span> triggers,
6368             it cn be used with any type of trigger to force the use of
6369             TCP for responses with owner names in a zone.
6370             </p>
6371 <div class="variablelist"><dl>
6372 <dt><span class="term"><span><strong class="command">PASSTHRU</strong></span></span></dt>
6373 <dd><p>
6374                     The whitelist policy is specified
6375                     by a CNAME whose target is <span><strong class="command">rpz-passthru</strong></span>.
6376                     It causes the response to not be rewritten
6377                     and is most often used to "poke holes" in policies for
6378                     CIDR blocks.
6379                   </p></dd>
6380 <dt><span class="term"><span><strong class="command">DROP</strong></span></span></dt>
6381 <dd><p>
6382                     The blacklist policy is specified
6383                     by a CNAME whose target is <span><strong class="command">rpz-drop</strong></span>.
6384                     It causes the response to be discarded.
6385                     Nothing is sent to the DNS client.
6386                   </p></dd>
6387 <dt><span class="term"><span><strong class="command">TCP-Only</strong></span></span></dt>
6388 <dd><p>
6389                     The "slip" policy is specified
6390                     by a CNAME whose target is <span><strong class="command">rpz-tcp-only</strong></span>.
6391                     It changes UDP responses to short, truncated DNS responses
6392                     that require the DNS client to try again with TCP.
6393                     It is used to mitigate distributed DNS reflection attacks.
6394                   </p></dd>
6395 <dt><span class="term"><span><strong class="command">NXDOMAIN</strong></span></span></dt>
6396 <dd><p>
6397                     The domain undefined response is encoded
6398                     by a CNAME whose target is the root domain (.)
6399                   </p></dd>
6400 <dt><span class="term"><span><strong class="command">NODATA</strong></span></span></dt>
6401 <dd><p>
6402                     The empty set of resource records is specified by
6403                     CNAME whose target is the wildcard top-level
6404                     domain (*.).
6405                     It rewrites the response to NODATA or ANCOUNT=1.
6406                   </p></dd>
6407 <dt><span class="term"><span><strong class="command">Local Data</strong></span></span></dt>
6408 <dd>
6409 <p>
6410                     A set of ordinary DNS records can be used to answer queries.
6411                     Queries for record types not the set are answered with
6412                     NODATA.
6413                   </p>
6414 <p>
6415                     A special form of local data is a CNAME whose target is a
6416                     wildcard such as *.example.com.
6417                     It is used as if were an ordinary CNAME after the astrisk (*)
6418                     has been replaced with the query name.
6419                     The purpose for this special form is query logging in the
6420                     walled garden's authority DNS server.
6421                   </p>
6422 </dd>
6423 </dl></div>
6424 <p>
6425           </p>
6426 <p>
6427             All of the actions specified in all of the individual records
6428             in a policy zone
6429             can be overridden with a <span><strong class="command">policy</strong></span> clause in the
6430             <span><strong class="command">response-policy</strong></span> option.
6431             An organization using a policy zone provided by another
6432             organization might use this mechanism to redirect domains
6433             to its own walled garden.
6434             </p>
6435 <div class="variablelist"><dl>
6436 <dt><span class="term"><span><strong class="command">GIVEN</strong></span></span></dt>
6437 <dd><p>The placeholder policy says "do not override but
6438                     perform the action specified in the zone."
6439                   </p></dd>
6440 <dt><span class="term"><span><strong class="command">DISABLED</strong></span></span></dt>
6441 <dd><p>
6442                     The testing override policy causes policy zone records to do
6443                     nothing but log what they would have done if the
6444                     policy zone were not disabled.
6445                     The response to the DNS query will be written (or not)
6446                     according to any triggered policy records that are not
6447                     disabled.
6448                     Disabled policy zones should appear first,
6449                     because they will often not be logged
6450                     if a higher precedence trigger is found first.
6451                   </p></dd>
6452 <dt>
6453 <span class="term"><span><strong class="command">PASSTHRU</strong></span>, </span><span class="term"><span><strong class="command">DROP</strong></span>, </span><span class="term"><span><strong class="command">TCP-Only</strong></span>, </span><span class="term"><span><strong class="command">NXDOMAIN</strong></span>, </span><span class="term"><span><strong class="command">NODATA</strong></span></span>
6454 </dt>
6455 <dd><p>
6456                     override with the corresponding per-record policy.
6457                   </p></dd>
6458 <dt><span class="term"><span><strong class="command">CNAME domain</strong></span></span></dt>
6459 <dd><p>
6460                       causes all RPZ policy records to act as if they were
6461                       "cname domain" records.
6462                     </p></dd>
6463 </dl></div>
6464 <p>
6465           </p>
6466 <p>
6467             By default, the actions encoded in a response policy zone
6468             are applied only to queries that ask for recursion (RD=1).
6469             That default can be changed for a single policy zone or
6470             all response policy zones in a view
6471             with a <span><strong class="command">recursive-only no</strong></span> clause.
6472             This feature is useful for serving the same zone files
6473             both inside and outside an RFC 1918 cloud and using RPZ to
6474             delete answers that would otherwise contain RFC 1918 values
6475             on the externally visible name server or view.
6476           </p>
6477 <p>
6478             Also by default, RPZ actions are applied only to DNS requests
6479             that either do not request DNSSEC metadata (DO=0) or when no
6480             DNSSEC records are available for request name in the original
6481             zone (not the response policy zone).  This default can be
6482             changed for all response policy zones in a view with a
6483             <span><strong class="command">break-dnssec yes</strong></span> clause.  In that case, RPZ
6484             actions are applied regardless of DNSSEC.  The name of the
6485             clause option reflects the fact that results rewritten by RPZ
6486             actions cannot verify.
6487           </p>
6488 <p>
6489             No DNS records are needed for a QNAME or Client-IP trigger.
6490             The name or IP address itself is sufficient,
6491             so in principle the query name need not be recursively resolved.
6492             However, not resolving the requested
6493             name can leak the fact that response policy rewriting is in use
6494             and that the name is listed in a policy zone to operators of
6495             servers for listed names.  To prevent that information leak, by
6496             default any recursion needed for a request is done before any
6497             policy triggers are considered.  Because listed domains often
6498             have slow authoritative servers, this default behavior can cost
6499             significant time.
6500             The <span><strong class="command">qname-wait-recurse no</strong></span> option
6501             overrides that default behavior when recursion cannot
6502             change a non-error response.
6503             The option does not affect QNAME or client-IP triggers
6504             in policy zones listed
6505             after other zones containing IP, NSIP and NSDNAME triggers, because
6506             those may depend on the A, AAAA, and NS records that would be
6507             found during recursive resolution.  It also does not affect
6508             DNSSEC requests (DO=1) unless <span><strong class="command">break-dnssec yes</strong></span>
6509             is in use, because the response would depend on whether or not
6510             RRSIG records were found during resolution.
6511             Using this option can cause error responses such as SERVFAIL to
6512             appear to be rewritten, since no recursion is being done to
6513             discover problems at the authoritative server.
6514           </p>
6515 <p>
6516             The TTL of a record modified by RPZ policies is set from the
6517             TTL of the relevant record in policy zone.  It is then limited
6518             to a maximum value.
6519             The <span><strong class="command">max-policy-ttl</strong></span> clause changes that
6520             maximum from its default of 5.
6521           </p>
6522 <p>
6523             For example, you might use this option statement
6524           </p>
6525 <pre class="programlisting">    response-policy { zone "badlist"; };</pre>
6526 <p>
6527             and this zone statement
6528           </p>
6529 <pre class="programlisting">    zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</pre>
6530 <p>
6531             with this zone file
6532           </p>
6533 <pre class="programlisting">$TTL 1H
6534 @                       SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
6535                         NS  LOCALHOST.
6536
6537 ; QNAME policy records.  There are no periods (.) after the owner names.
6538 nxdomain.domain.com     CNAME   .               ; NXDOMAIN policy
6539 *.nxdomain.domain.com   CNAME   .               ; NXDOMAIN policy
6540 nodata.domain.com       CNAME   *.              ; NODATA policy
6541 *.nodata.domain.com     CNAME   *.              ; NODATA policy
6542 bad.domain.com          A       10.0.0.1        ; redirect to a walled garden
6543                         AAAA    2001:2::1
6544 bzone.domain.com        CNAME   garden.example.com.
6545
6546 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
6547 ok.domain.com           CNAME   rpz-passthru.
6548
6549 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
6550 *.bzone.domain.com      CNAME   *.garden.example.com.
6551
6552
6553 ; IP policy records that rewrite all responses containing A records in 127/8
6554 ;       except 127.0.0.1
6555 8.0.0.0.127.rpz-ip      CNAME   .
6556 32.1.0.0.127.rpz-ip     CNAME   rpz-passthru.
6557
6558 ; NSDNAME and NSIP policy records
6559 ns.domain.com.rpz-nsdname   CNAME   .
6560 48.zz.2.2001.rpz-nsip       CNAME   .
6561
6562 ; blacklist and whitelist some DNS clients
6563 112.zz.2001.rpz-client-ip    CNAME   rpz-drop.
6564 8.0.0.0.127.rpz-client-ip    CNAME   rpz-drop.
6565
6566 ; force some DNS clients and responses in the example.com zone to TCP
6567 16.0.0.1.10.rpz-client-ip   CNAME   rpz-tcp-only.
6568 example.com                 CNAME   rpz-tcp-only.
6569 *.example.com               CNAME   rpz-tcp-only.
6570
6571 </pre>
6572 <p>
6573             RPZ can affect server performance.
6574             Each configured response policy zone requires the server to
6575             perform one to four additional database lookups before a
6576             query can be answered.
6577             For example, a DNS server with four policy zones, each with all
6578             four kinds of response triggers, QNAME, IP, NSIP, and
6579             NSDNAME, requires a total of 17 times as many database
6580             lookups as a similar DNS server with no response policy zones.
6581             A <acronym class="acronym">BIND9</acronym> server with adequate memory and one
6582             response policy zone with QNAME and IP triggers might achieve a
6583             maximum queries-per-second rate about 20% lower.
6584             A server with four response policy zones with QNAME and IP
6585             triggers might have a maximum QPS rate about 50% lower.
6586           </p>
6587 <p>
6588             Responses rewritten by RPZ are counted in the
6589             <span><strong class="command">RPZRewrites</strong></span> statistics.
6590           </p>
6591 </div>
6592 <div class="sect3" lang="en">
6593 <div class="titlepage"><div><div><h4 class="title">
6594 <a name="id2590393"></a>Response Rate Limiting</h4></div></div></div>
6595 <p>
6596             Excessive almost identical UDP <span class="emphasis"><em>responses</em></span>
6597             can be controlled by configuring a
6598             <span><strong class="command">rate-limit</strong></span> clause in an
6599             <span><strong class="command">options</strong></span> or <span><strong class="command">view</strong></span> statement.
6600             This mechanism keeps authoritative BIND 9 from being used
6601             in amplifying reflection denial of service (DoS) attacks.
6602             Short truncated (TC=1) responses can be sent to provide
6603             rate-limited responses to legitimate clients within
6604             a range of forged, attacked IP addresses.
6605             Legitimate clients react to dropped or truncated response
6606             by retrying with UDP or with TCP respectively.
6607           </p>
6608 <p>
6609             This mechanism is intended for authoritative DNS servers.
6610             It can be used on recursive servers but can slow
6611             applications such as SMTP servers (mail receivers) and
6612             HTTP clients (web browsers) that repeatedly request the
6613             same domains.
6614             When possible, closing "open" recursive servers is better.
6615           </p>
6616 <p>
6617             Response rate limiting uses a "credit" or "token bucket" scheme.
6618             Each combination of identical response and client
6619             has a conceptual account that earns a specified number
6620             of credits every second.
6621             A prospective response debits its account by one.
6622             Responses are dropped or truncated
6623             while the account is negative.
6624             Responses are tracked within a rolling window of time
6625             which defaults to 15 seconds, but can be configured with
6626             the <span><strong class="command">window</strong></span> option to any value from
6627             1 to 3600 seconds (1 hour).
6628             The account cannot become more positive than
6629             the per-second limit
6630             or more negative than <span><strong class="command">window</strong></span>
6631             times the per-second limit.
6632             When the specified number of credits for a class of
6633             responses is set to 0, those responses are not rate limited.
6634           </p>
6635 <p>
6636             The notions of "identical response" and "DNS client"
6637             for rate limiting are not simplistic.
6638             All responses to an address block are counted as if to a
6639             single client.
6640             The prefix lengths of addresses blocks are
6641             specified with <span><strong class="command">ipv4-prefix-length</strong></span> (default 24)
6642             and <span><strong class="command">ipv6-prefix-length</strong></span> (default 56).
6643           </p>
6644 <p>
6645             All non-empty responses for a valid domain name (qname)
6646             and record type (qtype) are identical and have a limit specified
6647             with <span><strong class="command">responses-per-second</strong></span>
6648             (default 0 or no limit).
6649             All empty (NODATA) responses for a valid domain,
6650             regardless of query type, are identical.
6651             Responses in the NODATA class are limited by
6652             <span><strong class="command">nodata-per-second</strong></span>
6653             (default <span><strong class="command">responses-per-second</strong></span>).
6654             Requests for any and all undefined subdomains of a given
6655             valid domain result in NXDOMAIN errors, and are identical
6656             regardless of query type.
6657             They are limited by <span><strong class="command">nxdomains-per-second</strong></span>
6658             (default base <span><strong class="command">responses-per-second</strong></span>).
6659             This controls some attacks using random names, but
6660             can be relaxed or turned off (set to 0)
6661             on servers that expect many legitimate
6662             NXDOMAIN responses, such as from anti-spam blacklists.
6663             Referrals or delegations to the server of a given
6664             domain are identical and are limited by
6665             <span><strong class="command">referrals-per-second</strong></span>
6666             (default <span><strong class="command">responses-per-second</strong></span>).
6667           </p>
6668 <p>
6669             Responses generated from local wildcards are counted and limited
6670             as if they were for the parent domain name.
6671             This controls flooding using random.wild.example.com.
6672           </p>
6673 <p>
6674             All requests that result in DNS errors other
6675             than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
6676             regardless of requested name (qname) or record type (qtype).
6677             This controls attacks using invalid requests or distant,
6678             broken authoritative servers.
6679             By default the limit on errors is the same as the
6680             <span><strong class="command">responses-per-second</strong></span> value,
6681             but it can be set separately with
6682             <span><strong class="command">errors-per-second</strong></span>.
6683           </p>
6684 <p>
6685             Many attacks using DNS involve UDP requests with forged source
6686             addresses.
6687             Rate limiting prevents the use of BIND 9 to flood a network
6688             with responses to requests with forged source addresses,
6689             but could let a third party block responses to legitimate requests.
6690             There is a mechanism that can answer some legitimate
6691             requests from a client whose address is being forged in a flood.
6692             Setting <span><strong class="command">slip</strong></span> to 2 (its default) causes every
6693             other UDP request to be answered with a small truncated (TC=1)
6694             response.
6695             The small size and reduced frequency, and so lack of
6696             amplification, of "slipped" responses make them unattractive
6697             for reflection DoS attacks.
6698             <span><strong class="command">slip</strong></span> must be between 0 and 10.
6699             A value of 0 does not "slip":
6700             no truncated responses are sent due to rate limiting,
6701             all responses are dropped.
6702             A value of 1 causes every response to slip;
6703             values between 2 and 10 cause every n'th response to slip.
6704             Some error responses including REFUSED and SERVFAIL
6705             cannot be replaced with truncated responses and are instead
6706             leaked at the <span><strong class="command">slip</strong></span> rate.
6707           </p>
6708 <p>
6709             (NOTE: Dropped responses from an authoritative server may
6710             reduce the difficulty of a third party successfully forging
6711             a response to a recursive resolver. The best security
6712             against forged responses is for authoritative operators
6713             to sign their zones using DNSSEC and for resolver operators
6714             to validate the responses. When this is not an option,
6715             operators who are more concerned with response integrity
6716             than with flood mitigation may consider setting
6717             <span><strong class="command">slip</strong></span> to 1, causing all rate-limited
6718             responses to be truncated rather than dropped.  This reduces
6719             the effectiveness of rate-limiting against reflection attacks.)
6720           </p>
6721 <p>
6722             When the approximate query per second rate exceeds
6723             the <span><strong class="command">qps-scale</strong></span> value,
6724             then the <span><strong class="command">responses-per-second</strong></span>,
6725             <span><strong class="command">errors-per-second</strong></span>,
6726             <span><strong class="command">nxdomains-per-second</strong></span> and
6727             <span><strong class="command">all-per-second</strong></span> values are reduced by the
6728             ratio of the current rate to the <span><strong class="command">qps-scale</strong></span> value.
6729             This feature can tighten defenses during attacks.
6730             For example, with
6731             <span><strong class="command">qps-scale 250; responses-per-second 20;</strong></span> and
6732             a total query rate of 1000 queries/second for all queries from
6733             all DNS clients including via TCP,
6734             then the effective responses/second limit changes to
6735             (250/1000)*20 or 5.
6736             Responses sent via TCP are not limited
6737             but are counted to compute the query per second rate.
6738           </p>
6739 <p>
6740             Communities of DNS clients can be given their own parameters or no
6741             rate limiting by putting
6742             <span><strong class="command">rate-limit</strong></span> statements in <span><strong class="command">view</strong></span>
6743             statements instead of the global <span><strong class="command">option</strong></span>
6744             statement.
6745             A <span><strong class="command">rate-limit</strong></span> statement in a view replaces,
6746             rather than supplementing, a <span><strong class="command">rate-limit</strong></span>
6747             statement among the main options.
6748             DNS clients within a view can be exempted from rate limits
6749             with the <span><strong class="command">exempt-clients</strong></span> clause.
6750           </p>
6751 <p>
6752             UDP responses of all kinds can be limited with the
6753             <span><strong class="command">all-per-second</strong></span> phrase.
6754             This rate limiting is unlike the rate limiting provided by
6755             <span><strong class="command">responses-per-second</strong></span>,
6756             <span><strong class="command">errors-per-second</strong></span>, and
6757             <span><strong class="command">nxdomains-per-second</strong></span> on a DNS server
6758             which are often invisible to the victim of a DNS reflection attack.
6759             Unless the forged requests of the attack are the same as the
6760             legitimate requests of the victim, the victim's requests are
6761             not affected.
6762             Responses affected by an <span><strong class="command">all-per-second</strong></span> limit
6763             are always dropped; the <span><strong class="command">slip</strong></span> value has no
6764             effect.
6765             An <span><strong class="command">all-per-second</strong></span> limit should be
6766             at least 4 times as large as the other limits,
6767             because single DNS clients often send bursts of legitimate
6768             requests.
6769             For example, the receipt of a single mail message can prompt
6770             requests from an SMTP server for NS, PTR, A, and AAAA records
6771             as the incoming SMTP/TCP/IP connection is considered.
6772             The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
6773             records as it considers the STMP <span><strong class="command">Mail From</strong></span>
6774             command.
6775             Web browsers often repeatedly resolve the same names that
6776             are repeated in HTML &lt;IMG&gt; tags in a page.
6777             <span><strong class="command">All-per-second</strong></span> is similar to the
6778             rate limiting offered by firewalls but often inferior.
6779             Attacks that justify ignoring the
6780             contents of DNS responses are likely to be attacks on the
6781             DNS server itself.
6782             They usually should be discarded before the DNS server
6783             spends resources making TCP connections or parsing DNS requests,
6784             but that rate limiting must be done before the
6785             DNS server sees the requests.
6786           </p>
6787 <p>
6788             The maximum size of the table used to track requests and
6789             rate limit responses is set with <span><strong class="command">max-table-size</strong></span>.
6790             Each entry in the table is between 40 and 80 bytes.
6791             The table needs approximately as many entries as the number
6792             of requests received per second.
6793             The default is 20,000.
6794             To reduce the cold start of growing the table,
6795             <span><strong class="command">min-table-size</strong></span> (default 500)
6796             can set the minimum table size.
6797             Enable <span><strong class="command">rate-limit</strong></span> category logging to monitor
6798             expansions of the table and inform
6799             choices for the initial and maximum table size.
6800           </p>
6801 <p>
6802             Use <span><strong class="command">log-only yes</strong></span> to test rate limiting parameters
6803             without actually dropping any requests.
6804           </p>
6805 <p>
6806             Responses dropped by rate limits are included in the
6807             <span><strong class="command">RateDropped</strong></span> and <span><strong class="command">QryDropped</strong></span>
6808             statistics.
6809             Responses that truncated by rate limits are included in
6810             <span><strong class="command">RateSlipped</strong></span> and <span><strong class="command">RespTruncated</strong></span>.
6811           </p>
6812 </div>
6813 </div>
6814 <div class="sect2" lang="en">
6815 <div class="titlepage"><div><div><h3 class="title">
6816 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
6817 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
6818     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6819     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6820     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6821     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6822     [<span class="optional"> request-sit <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6823     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6824     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6825     [<span class="optional"> nosit-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6826     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6827     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
6828     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
6829     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
6830     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6831     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6832     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6833     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6834     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6835                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6836     [<span class="optional"> query-source-v6 [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6837                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
6838     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6839     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
6840     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
6841 };
6842 </pre>
6843 </div>
6844 <div class="sect2" lang="en">
6845 <div class="titlepage"><div><div><h3 class="title">
6846 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
6847             Usage</h3></div></div></div>
6848 <p>
6849             The <span><strong class="command">server</strong></span> statement defines
6850             characteristics
6851             to be associated with a remote name server.  If a prefix length is
6852             specified, then a range of servers is covered.  Only the most
6853             specific
6854             server clause applies regardless of the order in
6855             <code class="filename">named.conf</code>.
6856           </p>
6857 <p>
6858             The <span><strong class="command">server</strong></span> statement can occur at
6859             the top level of the
6860             configuration file or inside a <span><strong class="command">view</strong></span>
6861             statement.
6862             If a <span><strong class="command">view</strong></span> statement contains
6863             one or more <span><strong class="command">server</strong></span> statements, only
6864             those
6865             apply to the view and any top-level ones are ignored.
6866             If a view contains no <span><strong class="command">server</strong></span>
6867             statements,
6868             any top-level <span><strong class="command">server</strong></span> statements are
6869             used as
6870             defaults.
6871           </p>
6872 <p>
6873             If you discover that a remote server is giving out bad data,
6874             marking it as bogus will prevent further queries to it. The
6875             default
6876             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
6877           </p>
6878 <p>
6879             The <span><strong class="command">provide-ixfr</strong></span> clause determines
6880             whether
6881             the local server, acting as master, will respond with an
6882             incremental
6883             zone transfer when the given remote server, a slave, requests it.
6884             If set to <span><strong class="command">yes</strong></span>, incremental transfer
6885             will be provided
6886             whenever possible. If set to <span><strong class="command">no</strong></span>,
6887             all transfers
6888             to the remote server will be non-incremental. If not set, the
6889             value
6890             of the <span><strong class="command">provide-ixfr</strong></span> option in the
6891             view or
6892             global options block is used as a default.
6893           </p>
6894 <p>
6895             The <span><strong class="command">request-ixfr</strong></span> clause determines
6896             whether
6897             the local server, acting as a slave, will request incremental zone
6898             transfers from the given remote server, a master. If not set, the
6899             value of the <span><strong class="command">request-ixfr</strong></span> option in
6900             the view or global options block is used as a default. It may
6901             also be set in the zone block and, if set there, it will
6902             override the global or view setting for that zone.
6903           </p>
6904 <p>
6905             IXFR requests to servers that do not support IXFR will
6906             automatically
6907             fall back to AXFR.  Therefore, there is no need to manually list
6908             which servers support IXFR and which ones do not; the global
6909             default
6910             of <span><strong class="command">yes</strong></span> should always work.
6911             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
6912             <span><strong class="command">request-ixfr</strong></span> clauses is
6913             to make it possible to disable the use of IXFR even when both
6914             master
6915             and slave claim to support it, for example if one of the servers
6916             is buggy and crashes or corrupts data when IXFR is used.
6917           </p>
6918 <p>
6919             The <span><strong class="command">edns</strong></span> clause determines whether
6920             the local server will attempt to use EDNS when communicating
6921             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
6922           </p>
6923 <p>
6924             The <span><strong class="command">edns-udp-size</strong></span> option sets the
6925             EDNS UDP size that is advertised by <span><strong class="command">named</strong></span>
6926             when querying the remote server.  Valid values are 512
6927             to 4096 bytes (values outside this range will be silently
6928             adjusted to the nearest value within it).  This option
6929             is useful when you wish to advertise a different value
6930             to this server than the value you advertise globally,
6931             for example, when there is a firewall at the remote
6932             site that is blocking large replies. (Note: Currently,
6933             this sets a single UDP size for all packets sent to the
6934             server; <span><strong class="command">named</strong></span> will not deviate from
6935             this value.  This differs from the behavior of
6936             <span><strong class="command">edns-udp-size</strong></span> in <span><strong class="command">options</strong></span>
6937             or <span><strong class="command">view</strong></span> statements, where it specifies
6938             a maximum value. The <span><strong class="command">server</strong></span> statement
6939             behavior may be brought into conformance with the
6940             <span><strong class="command">options/view</strong></span> behavior in future releases.)
6941           </p>
6942 <p>
6943             The <span><strong class="command">max-udp-size</strong></span> option sets the
6944             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
6945             values are 512 to 4096 bytes (values outside this range will
6946             be silently adjusted).  This option is useful when you
6947             know that there is a firewall that is blocking large
6948             replies from <span><strong class="command">named</strong></span>.
6949           </p>
6950 <p>
6951             The <span><strong class="command">nosit-udp-size</strong></span> option sets the
6952             maximum size of UDP responses that will be sent to
6953             queries without a valid source identity token.  The command
6954             <span><strong class="command">max-udp-size</strong></span> option may further limit
6955             the response size.
6956           </p>
6957 <p>
6958             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
6959             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
6960             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
6961             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
6962             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
6963             4.9.5. You can specify which method
6964             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
6965             If <span><strong class="command">transfer-format</strong></span> is not
6966             specified, the <span><strong class="command">transfer-format</strong></span>
6967             specified
6968             by the <span><strong class="command">options</strong></span> statement will be
6969             used.
6970           </p>
6971 <p><span><strong class="command">transfers</strong></span>
6972             is used to limit the number of concurrent inbound zone
6973             transfers from the specified server. If no
6974             <span><strong class="command">transfers</strong></span> clause is specified, the
6975             limit is set according to the
6976             <span><strong class="command">transfers-per-ns</strong></span> option.
6977           </p>
6978 <p>
6979             The <span><strong class="command">keys</strong></span> clause identifies a
6980             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
6981             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
6982             when talking to the remote server.
6983             When a request is sent to the remote server, a request signature
6984             will be generated using the key specified here and appended to the
6985             message. A request originating from the remote server is not
6986             required
6987             to be signed by this key.
6988           </p>
6989 <p>
6990             Although the grammar of the <span><strong class="command">keys</strong></span>
6991             clause
6992             allows for multiple keys, only a single key per server is
6993             currently
6994             supported.
6995           </p>
6996 <p>
6997             The <span><strong class="command">transfer-source</strong></span> and
6998             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
6999             the IPv4 and IPv6 source
7000             address to be used for zone transfer with the remote server,
7001             respectively.
7002             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
7003             be specified.
7004             Similarly, for an IPv6 remote server, only
7005             <span><strong class="command">transfer-source-v6</strong></span> can be
7006             specified.
7007             For more details, see the description of
7008             <span><strong class="command">transfer-source</strong></span> and
7009             <span><strong class="command">transfer-source-v6</strong></span> in
7010             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7011           </p>
7012 <p>
7013             The <span><strong class="command">notify-source</strong></span> and
7014             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
7015             IPv4 and IPv6 source address to be used for notify
7016             messages sent to remote servers, respectively.  For an
7017             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
7018             can be specified.  Similarly, for an IPv6 remote server,
7019             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
7020           </p>
7021 <p>
7022             The <span><strong class="command">query-source</strong></span> and
7023             <span><strong class="command">query-source-v6</strong></span> clauses specify the
7024             IPv4 and IPv6 source address to be used for queries
7025             sent to remote servers, respectively.  For an IPv4
7026             remote server, only <span><strong class="command">query-source</strong></span> can
7027             be specified.  Similarly, for an IPv6 remote server,
7028             only <span><strong class="command">query-source-v6</strong></span> can be specified.
7029           </p>
7030 <p>
7031             The <span><strong class="command">request-nsid</strong></span> clause determines
7032             whether the local server will add a NSID EDNS option
7033             to requests sent to the server.  This overrides
7034             <span><strong class="command">request-nsid</strong></span> set at the view or
7035             option level.
7036           </p>
7037 <p>
7038             The <span><strong class="command">request-sit</strong></span> clause determines
7039             whether the local server will add a SIT EDNS option
7040             to requests sent to the server.  This overrides
7041             <span><strong class="command">request-sit</strong></span> set at the view or
7042             option level.  Named may determine that SIT is not
7043             supported by the remote server and not add a SIT
7044             EDNS option to requests.
7045           </p>
7046 </div>
7047 <div class="sect2" lang="en">
7048 <div class="titlepage"><div><div><h3 class="title">
7049 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
7050 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
7051    [ inet ( ip_addr | * ) [ port ip_port ]
7052    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
7053    [ inet ...; ]
7054 };
7055 </pre>
7056 </div>
7057 <div class="sect2" lang="en">
7058 <div class="titlepage"><div><div><h3 class="title">
7059 <a name="id2591758"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
7060             Usage</h3></div></div></div>
7061 <p>
7062           The <span><strong class="command">statistics-channels</strong></span> statement
7063           declares communication channels to be used by system
7064           administrators to get access to statistics information of
7065           the name server.
7066         </p>
7067 <p>
7068           This statement intends to be flexible to support multiple
7069           communication protocols in the future, but currently only
7070           HTTP access is supported.
7071           It requires that BIND 9 be compiled with libxml2 and/or
7072           json-c (also known as libjson0); the
7073           <span><strong class="command">statistics-channels</strong></span> statement is
7074           still accepted even if it is built without the library,
7075           but any HTTP access will fail with an error.
7076         </p>
7077 <p>
7078           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
7079           listening at the specified <span><strong class="command">ip_port</strong></span> on the
7080           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
7081           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code>
7082           (asterisk) is
7083           interpreted as the IPv4 wildcard address; connections will be
7084           accepted on any of the system's IPv4 addresses.
7085           To listen on the IPv6 wildcard address,
7086           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
7087         </p>
7088 <p>
7089           If no port is specified, port 80 is used for HTTP channels.
7090           The asterisk "<code class="literal">*</code>" cannot be used for
7091           <span><strong class="command">ip_port</strong></span>.
7092         </p>
7093 <p>
7094           The attempt of opening a statistics channel is
7095           restricted by the optional <span><strong class="command">allow</strong></span> clause.
7096           Connections to the statistics channel are permitted based on the
7097           <span><strong class="command">address_match_list</strong></span>.
7098           If no <span><strong class="command">allow</strong></span> clause is present,
7099           <span><strong class="command">named</strong></span> accepts connection
7100           attempts from any address; since the statistics may
7101           contain sensitive internal information, it is highly
7102           recommended to restrict the source of connection requests
7103           appropriately.
7104         </p>
7105 <p>
7106           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
7107           <span><strong class="command">named</strong></span> will not open any communication channels.
7108         </p>
7109 <p>
7110           The statistics are available in various formats and views
7111           depending on the URI used to access them.  For example, if
7112           the statistics channel is configured to listen on 127.0.0.1
7113           port 8888, then the statistics are accessible in XML format at
7114           <a href="http://127.0.0.1:8888/" target="_top">http://127.0.0.1:8888/</a> or
7115           <a href="http://127.0.0.1:8888/xml" target="_top">http://127.0.0.1:8888/xml</a>. A CSS file is
7116           included which can format the XML statistics into tables
7117           when viewed with a stylesheet-capable browser, and into
7118           charts and graphs using the Google Charts API when using a
7119           javascript-capable browser.
7120         </p>
7121 <p>
7122           Applications that depend on a particular XML schema
7123           can request
7124           <a href="http://127.0.0.1:8888/xml/v2" target="_top">http://127.0.0.1:8888/xml/v2</a> for version 2
7125           of the statistics XML schema or
7126           <a href="http://127.0.0.1:8888/xml/v3" target="_top">http://127.0.0.1:8888/xml/v3</a> for version 3.
7127           If the requested schema is supported by the server, then
7128           it will respond; if not, it will return a "page not found"
7129           error.
7130         </p>
7131 <p>
7132           Broken-out subsets of the statistics can be viewed at
7133           <a href="http://127.0.0.1:8888/xml/v3/status" target="_top">http://127.0.0.1:8888/xml/v3/status</a>
7134           (server uptime and last reconfiguration time),
7135           <a href="http://127.0.0.1:8888/xml/v3/server" target="_top">http://127.0.0.1:8888/xml/v3/server</a>
7136           (server and resolver statistics),
7137           <a href="http://127.0.0.1:8888/xml/v3/zones" target="_top">http://127.0.0.1:8888/xml/v3/zones</a>
7138           (zone statistics),
7139           <a href="http://127.0.0.1:8888/xml/v3/net" target="_top">http://127.0.0.1:8888/xml/v3/net</a>
7140           (network status and socket statistics),
7141           <a href="http://127.0.0.1:8888/xml/v3/mem" target="_top">http://127.0.0.1:8888/xml/v3/mem</a>
7142           (memory manager statistics),
7143           <a href="http://127.0.0.1:8888/xml/v3/tasks" target="_top">http://127.0.0.1:8888/xml/v3/tasks</a>
7144           (task manager statistics).
7145         </p>
7146 <p>
7147           The full set of statistics can also be read in JSON format at
7148           <a href="http://127.0.0.1:8888/json" target="_top">http://127.0.0.1:8888/json</a>,
7149           with the broken-out subsets at
7150           <a href="http://127.0.0.1:8888/json/v1/status" target="_top">http://127.0.0.1:8888/json/v1/status</a>
7151           (server uptime and last reconfiguration time),
7152           <a href="http://127.0.0.1:8888/json/v1/server" target="_top">http://127.0.0.1:8888/json/v1/server</a>
7153           (server and resolver statistics),
7154           <a href="http://127.0.0.1:8888/json/v1/zones" target="_top">http://127.0.0.1:8888/json/v1/zones</a>
7155           (zone statistics),
7156           <a href="http://127.0.0.1:8888/json/v1/net" target="_top">http://127.0.0.1:8888/json/v1/net</a>
7157           (network status and socket statistics),
7158           <a href="http://127.0.0.1:8888/json/v1/mem" target="_top">http://127.0.0.1:8888/json/v1/mem</a>
7159           (memory manager statistics),
7160           <a href="http://127.0.0.1:8888/json/v1/tasks" target="_top">http://127.0.0.1:8888/json/v1/tasks</a>
7161           (task manager statistics).
7162         </p>
7163 </div>
7164 <div class="sect2" lang="en">
7165 <div class="titlepage"><div><div><h3 class="title">
7166 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
7167 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
7168     <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ;
7169     [<span class="optional"> <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; [<span class="optional">...</span>]</span>]
7170 };
7171 </pre>
7172 </div>
7173 <div class="sect2" lang="en">
7174 <div class="titlepage"><div><div><h3 class="title">
7175 <a name="id2592176"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
7176             and Usage</h3></div></div></div>
7177 <p>
7178             The <span><strong class="command">trusted-keys</strong></span> statement defines
7179             DNSSEC security roots. DNSSEC is described in <a href="Bv9ARM.ch04.html#DNSSEC" title="DNSSEC">the section called &#8220;DNSSEC&#8221;</a>. A security root is defined when the
7180             public key for a non-authoritative zone is known, but
7181             cannot be securely obtained through DNS, either because
7182             it is the DNS root zone or because its parent zone is
7183             unsigned.  Once a key has been configured as a trusted
7184             key, it is treated as if it had been validated and
7185             proven secure. The resolver attempts DNSSEC validation
7186             on all DNS data in subdomains of a security root.
7187           </p>
7188 <p>
7189             All keys (and corresponding zones) listed in
7190             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
7191             of what parent zones say.  Similarly for all keys listed in
7192             <span><strong class="command">trusted-keys</strong></span> only those keys are
7193             used to validate the DNSKEY RRset.  The parent's DS RRset
7194             will not be used.
7195           </p>
7196 <p>
7197             The <span><strong class="command">trusted-keys</strong></span> statement can contain
7198             multiple key entries, each consisting of the key's
7199             domain name, flags, protocol, algorithm, and the Base-64
7200             representation of the key data.
7201             Spaces, tabs, newlines and carriage returns are ignored
7202             in the key data, so the configuration may be split up into
7203             multiple lines.
7204           </p>
7205 <p>
7206             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
7207             of <code class="filename">named.conf</code> or within a view.  If it is
7208             set in both places, they are additive: keys defined at the top
7209             level are inherited by all views, but keys defined in a view
7210             are only used within that view.
7211           </p>
7212 </div>
7213 <div class="sect2" lang="en">
7214 <div class="titlepage"><div><div><h3 class="title">
7215 <a name="id2592222"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
7216 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
7217     <em class="replaceable"><code>name</code></em> initial-key <em class="replaceable"><code>flags</code></em> <em class="replaceable"><code>protocol</code></em> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>key-data</code></em> ;
7218     [<span class="optional"> <em class="replaceable"><code>name</code></em> initial-key <em class="replaceable"><code>flags</code></em> <em class="replaceable"><code>protocol</code></em> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>key-data</code></em> ; [<span class="optional">...</span>]</span>]
7219 };
7220 </pre>
7221 </div>
7222 <div class="sect2" lang="en">
7223 <div class="titlepage"><div><div><h3 class="title">
7224 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
7225             and Usage</h3></div></div></div>
7226 <p>
7227             The <span><strong class="command">managed-keys</strong></span> statement, like
7228             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
7229             security roots.  The difference is that
7230             <span><strong class="command">managed-keys</strong></span> can be kept up to date
7231             automatically, without intervention from the resolver
7232             operator.
7233           </p>
7234 <p>
7235             Suppose, for example, that a zone's key-signing
7236             key was compromised, and the zone owner had to revoke and
7237             replace the key.  A resolver which had the old key in a
7238             <span><strong class="command">trusted-keys</strong></span> statement would be
7239             unable to validate this zone any longer; it would
7240             reply with a SERVFAIL response code.  This would
7241             continue until the resolver operator had updated the
7242             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
7243           </p>
7244 <p>
7245             If, however, the zone were listed in a
7246             <span><strong class="command">managed-keys</strong></span> statement instead, then the
7247             zone owner could add a "stand-by" key to the zone in advance.
7248             <span><strong class="command">named</strong></span> would store the stand-by key, and
7249             when the original key was revoked, <span><strong class="command">named</strong></span>
7250             would be able to transition smoothly to the new key.  It would
7251             also recognize that the old key had been revoked, and cease
7252             using that key to validate answers, minimizing the damage that
7253             the compromised key could do.
7254           </p>
7255 <p>
7256             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
7257             the keys to be managed, along with information about how the
7258             keys are to be initialized for the first time.  The only
7259             initialization method currently supported (as of
7260             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
7261             This means the <span><strong class="command">managed-keys</strong></span> statement must
7262             contain a copy of the initializing key.  (Future releases may
7263             allow keys to be initialized by other methods, eliminating this
7264             requirement.)
7265           </p>
7266 <p>
7267             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
7268             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
7269             in the presence of the second field, containing the keyword
7270             <code class="literal">initial-key</code>.  The difference is, whereas the
7271             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
7272             trusted until they are removed from
7273             <code class="filename">named.conf</code>, an initializing key listed
7274             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
7275             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
7276             managed key database and start the RFC 5011 key maintenance
7277             process.
7278           </p>
7279 <p>
7280             The first time <span><strong class="command">named</strong></span> runs with a managed key
7281             configured in <code class="filename">named.conf</code>, it fetches the
7282             DNSKEY RRset directly from the zone apex, and validates it
7283             using the key specified in the <span><strong class="command">managed-keys</strong></span>
7284             statement.  If the DNSKEY RRset is validly signed, then it is
7285             used as the basis for a new managed keys database.
7286           </p>
7287 <p>
7288             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
7289             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
7290             make sure RFC 5011 key maintenance has already been initialized
7291             for the specified domain, and if so, it simply moves on.  The
7292             key specified in the <span><strong class="command">managed-keys</strong></span> is not
7293             used to validate answers; it has been superseded by the key or
7294             keys stored in the managed keys database.
7295           </p>
7296 <p>
7297             The next time <span><strong class="command">named</strong></span> runs after a name
7298             has been <span class="emphasis"><em>removed</em></span> from the
7299             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
7300             zone will be removed from the managed keys database,
7301             and RFC 5011 key maintenance will no longer be used for that
7302             domain.
7303           </p>
7304 <p>
7305             <span><strong class="command">named</strong></span> only maintains a single managed keys
7306             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
7307             <span><strong class="command">managed-keys</strong></span> may only be set at the top
7308             level of <code class="filename">named.conf</code>, not within a view.
7309           </p>
7310 <p>
7311             In the current implementation, the managed keys database is
7312             stored as a master-format zone file called
7313             <code class="filename">managed-keys.bind</code>.  When the key database
7314             is changed, the zone is updated.  As with any other dynamic
7315             zone, changes will be written into a journal file,
7316             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
7317             to the master file as soon as possible afterward; in the case
7318             of the managed key database, this will usually occur within 30
7319             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
7320             automatic key maintenance, those two files can be expected to
7321             exist in the working directory.  (For this reason among others,
7322             the working directory should be always be writable by
7323             <span><strong class="command">named</strong></span>.)
7324           </p>
7325 <p>
7326             If the <span><strong class="command">dnssec-validation</strong></span> option is
7327             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
7328             will automatically initialize a managed key for the
7329             root zone.  Similarly, if the <span><strong class="command">dnssec-lookaside</strong></span>
7330             option is set to <strong class="userinput"><code>auto</code></strong>,
7331             <span><strong class="command">named</strong></span> will automatically initialize
7332             a managed key for the zone <code class="literal">dlv.isc.org</code>.
7333             In both cases, the key that is used to initialize the key
7334             maintenance process is built into <span><strong class="command">named</strong></span>,
7335             and can be overridden from <span><strong class="command">bindkeys-file</strong></span>.
7336           </p>
7337 </div>
7338 <div class="sect2" lang="en">
7339 <div class="titlepage"><div><div><h3 class="title">
7340 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
7341 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
7342       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7343       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
7344       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
7345       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
7346       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
7347       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
7348 };
7349 </pre>
7350 </div>
7351 <div class="sect2" lang="en">
7352 <div class="titlepage"><div><div><h3 class="title">
7353 <a name="id2592589"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
7354 <p>
7355             The <span><strong class="command">view</strong></span> statement is a powerful
7356             feature
7357             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
7358             answer a DNS query differently
7359             depending on who is asking. It is particularly useful for
7360             implementing
7361             split DNS setups without having to run multiple servers.
7362           </p>
7363 <p>
7364             Each <span><strong class="command">view</strong></span> statement defines a view
7365             of the
7366             DNS namespace that will be seen by a subset of clients.  A client
7367             matches
7368             a view if its source IP address matches the
7369             <code class="varname">address_match_list</code> of the view's
7370             <span><strong class="command">match-clients</strong></span> clause and its
7371             destination IP address matches
7372             the <code class="varname">address_match_list</code> of the
7373             view's
7374             <span><strong class="command">match-destinations</strong></span> clause.  If not
7375             specified, both
7376             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
7377             default to matching all addresses.  In addition to checking IP
7378             addresses
7379             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
7380             can also take <span><strong class="command">keys</strong></span> which provide an
7381             mechanism for the
7382             client to select the view.  A view can also be specified
7383             as <span><strong class="command">match-recursive-only</strong></span>, which
7384             means that only recursive
7385             requests from matching clients will match that view.
7386             The order of the <span><strong class="command">view</strong></span> statements is
7387             significant &#8212;
7388             a client request will be resolved in the context of the first
7389             <span><strong class="command">view</strong></span> that it matches.
7390           </p>
7391 <p>
7392             Zones defined within a <span><strong class="command">view</strong></span>
7393             statement will
7394             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
7395             By defining a zone of the same name in multiple views, different
7396             zone data can be given to different clients, for example,
7397             "internal"
7398             and "external" clients in a split DNS setup.
7399           </p>
7400 <p>
7401             Many of the options given in the <span><strong class="command">options</strong></span> statement
7402             can also be used within a <span><strong class="command">view</strong></span>
7403             statement, and then
7404             apply only when resolving queries with that view.  When no
7405             view-specific
7406             value is given, the value in the <span><strong class="command">options</strong></span> statement
7407             is used as a default.  Also, zone options can have default values
7408             specified
7409             in the <span><strong class="command">view</strong></span> statement; these
7410             view-specific defaults
7411             take precedence over those in the <span><strong class="command">options</strong></span> statement.
7412           </p>
7413 <p>
7414             Views are class specific.  If no class is given, class IN
7415             is assumed.  Note that all non-IN views must contain a hint zone,
7416             since only the IN class has compiled-in default hints.
7417           </p>
7418 <p>
7419             If there are no <span><strong class="command">view</strong></span> statements in
7420             the config
7421             file, a default view that matches any client is automatically
7422             created
7423             in class IN. Any <span><strong class="command">zone</strong></span> statements
7424             specified on
7425             the top level of the configuration file are considered to be part
7426             of
7427             this default view, and the <span><strong class="command">options</strong></span>
7428             statement will
7429             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
7430             statements are present, all <span><strong class="command">zone</strong></span>
7431             statements must
7432             occur inside <span><strong class="command">view</strong></span> statements.
7433           </p>
7434 <p>
7435             Here is an example of a typical split DNS setup implemented
7436             using <span><strong class="command">view</strong></span> statements:
7437           </p>
7438 <pre class="programlisting">view "internal" {
7439       // This should match our internal networks.
7440       match-clients { 10.0.0.0/8; };
7441
7442       // Provide recursive service to internal
7443       // clients only.
7444       recursion yes;
7445
7446       // Provide a complete view of the example.com
7447       // zone including addresses of internal hosts.
7448       zone "example.com" {
7449             type master;
7450             file "example-internal.db";
7451       };
7452 };
7453
7454 view "external" {
7455       // Match all clients not matched by the
7456       // previous view.
7457       match-clients { any; };
7458
7459       // Refuse recursive service to external clients.
7460       recursion no;
7461
7462       // Provide a restricted view of the example.com
7463       // zone containing only publicly accessible hosts.
7464       zone "example.com" {
7465            type master;
7466            file "example-external.db";
7467       };
7468 };
7469 </pre>
7470 </div>
7471 <div class="sect2" lang="en">
7472 <div class="titlepage"><div><div><h3 class="title">
7473 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
7474             Statement Grammar</h3></div></div></div>
7475 <pre class="programlisting"><span><strong class="command">zone</strong></span> <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7476     type master;
7477     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7478     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7479     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7480     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7481     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7482     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7483     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7484     [<span class="optional"> update-policy <em class="replaceable"><code>local</code></em> | { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
7485     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ;
7486                   [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
7487     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7488     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7489     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7490     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
7491     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7492     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7493     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7494     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>|<code class="constant">map</code>) ; </span>]
7495     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7496     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7497     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7498     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
7499     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7500     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7501     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7502     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7503     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7504     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7505     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7506     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7507     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
7508     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7509     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7510     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7511     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7512     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7513     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7514     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
7515     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7516     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7517     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7518     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7519     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7520     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7521     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7522     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7523     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7524     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7525     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7526     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7527     [<span class="optional"> serial-update-method <code class="constant">increment</code>|<code class="constant">unixtime</code>; </span>]
7528     [<span class="optional"> max-zone-ttl <em class="replaceable"><code>number</code></em> ; </span>]
7529 };
7530
7531 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7532     type slave;
7533     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7534     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7535     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7536     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7537     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7538     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
7539     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7540     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7541     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7542     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7543     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7544     [<span class="optional"> also-notify [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7545                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7546                               [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>]
7547                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7548     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7549     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7550     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7551     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>|<code class="constant">map</code>) ; </span>]
7552     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7553     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7554     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7555     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
7556     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7557     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7558     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7559     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7560     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7561                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7562                               [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>]
7563                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7564     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7565     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7566     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7567     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7568     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7569     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
7570     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7571     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7572     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7573     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7574     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7575     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7576     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7577                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7578                              [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7579     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7580     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7581     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7582     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7583     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
7584     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7585     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7586     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7587     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7588     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7589     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7590     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7591     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7592     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7593     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7594     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7595     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7596     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7597 };
7598
7599 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7600     type hint;
7601     file <em class="replaceable"><code>string</code></em> ;
7602     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7603     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
7604 };
7605
7606 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7607     type stub;
7608     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7609     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7610     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7611     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7612     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7613     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7614     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>|<code class="constant">map</code>) ; </span>]
7615     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7616     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
7617     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7618                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7619                               [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>]
7620                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7621     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7622     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7623     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7624     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7625     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7626                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7627     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7628     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7629                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; </span>]
7630     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7631     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7632     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7633     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7634     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7635     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7636     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7637     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7638 };
7639
7640 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7641     type static-stub;
7642     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7643     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
7644     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
7645     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7646 };
7647
7648 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7649     type forward;
7650     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7651     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">dscp <em class="replaceable"><code>ip_dscp</code></em></span>] ; ... </span>] }; </span>]
7652     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7653 };
7654
7655 zone <em class="replaceable"><code>"."</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7656     type redirect;
7657     file <em class="replaceable"><code>string</code></em> ;
7658     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>|<code class="constant">map</code>) ; </span>]
7659     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7660     [<span class="optional"> max-zone-ttl <em class="replaceable"><code>number</code></em> ; </span>]
7661 };
7662
7663 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7664     type delegation-only;
7665 };
7666
7667 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7668     [<span class="optional"> in-view <em class="replaceable"><code>string</code></em> ; </span>]
7669 };
7670
7671 </pre>
7672 </div>
7673 <div class="sect2" lang="en">
7674 <div class="titlepage"><div><div><h3 class="title">
7675 <a name="id2594602"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
7676 <div class="sect3" lang="en">
7677 <div class="titlepage"><div><div><h4 class="title">
7678 <a name="id2594610"></a>Zone Types</h4></div></div></div>
7679 <div class="informaltable"><table border="1">
7680 <colgroup>
7681 <col>
7682 <col>
7683 </colgroup>
7684 <tbody>
7685 <tr>
7686 <td>
7687                       <p>
7688                         <code class="varname">master</code>
7689                       </p>
7690                     </td>
7691 <td>
7692                       <p>
7693                         The server has a master copy of the data
7694                         for the zone and will be able to provide authoritative
7695                         answers for
7696                         it.
7697                       </p>
7698                     </td>
7699 </tr>
7700 <tr>
7701 <td>
7702                       <p>
7703                         <code class="varname">slave</code>
7704                       </p>
7705                     </td>
7706 <td>
7707                       <p>
7708                         A slave zone is a replica of a master
7709                         zone. The <span><strong class="command">masters</strong></span> list
7710                         specifies one or more IP addresses
7711                         of master servers that the slave contacts to update
7712                         its copy of the zone.
7713                         Masters list elements can also be names of other
7714                         masters lists.
7715                         By default, transfers are made from port 53 on the
7716                         servers; this can
7717                         be changed for all servers by specifying a port number
7718                         before the
7719                         list of IP addresses, or on a per-server basis after
7720                         the IP address.
7721                         Authentication to the master can also be done with
7722                         per-server TSIG keys.
7723                         If a file is specified, then the
7724                         replica will be written to this file whenever the zone
7725                         is changed,
7726                         and reloaded from this file on a server restart. Use
7727                         of a file is
7728                         recommended, since it often speeds server startup and
7729                         eliminates
7730                         a needless waste of bandwidth. Note that for large
7731                         numbers (in the
7732                         tens or hundreds of thousands) of zones per server, it
7733                         is best to
7734                         use a two-level naming scheme for zone filenames. For
7735                         example,
7736                         a slave server for the zone <code class="literal">example.com</code> might place
7737                         the zone contents into a file called
7738                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
7739                         just the first two letters of the zone name. (Most
7740                         operating systems
7741                         behave very slowly if you put 100000 files into
7742                         a single directory.)
7743                       </p>
7744                     </td>
7745 </tr>
7746 <tr>
7747 <td>
7748                       <p>
7749                         <code class="varname">stub</code>
7750                       </p>
7751                     </td>
7752 <td>
7753                       <p>
7754                         A stub zone is similar to a slave zone,
7755                         except that it replicates only the NS records of a
7756                         master zone instead
7757                         of the entire zone. Stub zones are not a standard part
7758                         of the DNS;
7759                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
7760                       </p>
7761
7762                       <p>
7763                         Stub zones can be used to eliminate the need for glue
7764                         NS record
7765                         in a parent zone at the expense of maintaining a stub
7766                         zone entry and
7767                         a set of name server addresses in <code class="filename">named.conf</code>.
7768                         This usage is not recommended for new configurations,
7769                         and BIND 9
7770                         supports it only in a limited way.
7771                         In <acronym class="acronym">BIND</acronym> 4/8, zone
7772                         transfers of a parent zone
7773                         included the NS records from stub children of that
7774                         zone. This meant
7775                         that, in some cases, users could get away with
7776                         configuring child stubs
7777                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
7778                         9 never mixes together zone data from different zones
7779                         in this
7780                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
7781                         zone has child stub zones configured, all the slave
7782                         servers for the
7783                         parent zone also need to have the same child stub
7784                         zones
7785                         configured.
7786                       </p>
7787
7788                       <p>
7789                         Stub zones can also be used as a way of forcing the
7790                         resolution
7791                         of a given domain to use a particular set of
7792                         authoritative servers.
7793                         For example, the caching name servers on a private
7794                         network using
7795                         RFC1918 addressing may be configured with stub zones
7796                         for
7797                         <code class="literal">10.in-addr.arpa</code>
7798                         to use a set of internal name servers as the
7799                         authoritative
7800                         servers for that domain.
7801                       </p>
7802                     </td>
7803 </tr>
7804 <tr>
7805 <td>
7806                       <p>
7807                         <code class="varname">static-stub</code>
7808                       </p>
7809                     </td>
7810 <td>
7811                       <p>
7812                         A static-stub zone is similar to a stub zone
7813                         with the following exceptions:
7814                         the zone data is statically configured, rather
7815                         than transferred from a master server;
7816                         when recursion is necessary for a query that
7817                         matches a static-stub zone, the locally
7818                         configured data (nameserver names and glue addresses)
7819                         is always used even if different authoritative
7820                         information is cached.
7821                       </p>
7822                       <p>
7823                         Zone data is configured via the
7824                         <span><strong class="command">server-addresses</strong></span> and
7825                         <span><strong class="command">server-names</strong></span> zone options.
7826                       </p>
7827                       <p>
7828                         The zone data is maintained in the form of NS
7829                         and (if necessary) glue A or AAAA RRs
7830                         internally, which can be seen by dumping zone
7831                         databases by <span><strong class="command">rndc dumpdb -all</strong></span>.
7832                         The configured RRs are considered local configuration
7833                         parameters rather than public data.
7834                         Non recursive queries (i.e., those with the RD
7835                         bit off) to a static-stub zone are therefore
7836                         prohibited and will be responded with REFUSED.
7837                       </p>
7838                       <p>
7839                         Since the data is statically configured, no
7840                         zone maintenance action takes place for a static-stub
7841                         zone.
7842                         For example, there is no periodic refresh
7843                         attempt, and an incoming notify message
7844                         will be rejected with an rcode of NOTAUTH.
7845                       </p>
7846                       <p>
7847                         Each static-stub zone is configured with
7848                         internally generated NS and (if necessary)
7849                         glue A or AAAA RRs
7850                       </p>
7851                     </td>
7852 </tr>
7853 <tr>
7854 <td>
7855                       <p>
7856                         <code class="varname">forward</code>
7857                       </p>
7858                     </td>
7859 <td>
7860                       <p>
7861                         A "forward zone" is a way to configure
7862                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
7863                         of type <span><strong class="command">forward</strong></span> can
7864                         contain a <span><strong class="command">forward</strong></span>
7865                         and/or <span><strong class="command">forwarders</strong></span>
7866                         statement,
7867                         which will apply to queries within the domain given by
7868                         the zone
7869                         name. If no <span><strong class="command">forwarders</strong></span>
7870                         statement is present or
7871                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
7872                         forwarding will be done for the domain, canceling the
7873                         effects of
7874                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
7875                         if you want to use this type of zone to change the
7876                         behavior of the
7877                         global <span><strong class="command">forward</strong></span> option
7878                         (that is, "forward first"
7879                         to, then "forward only", or vice versa, but want to
7880                         use the same
7881                         servers as set globally) you need to re-specify the
7882                         global forwarders.
7883                       </p>
7884                     </td>
7885 </tr>
7886 <tr>
7887 <td>
7888                       <p>
7889                         <code class="varname">hint</code>
7890                       </p>
7891                     </td>
7892 <td>
7893                       <p>
7894                         The initial set of root name servers is
7895                         specified using a "hint zone". When the server starts
7896                         up, it uses
7897                         the root hints to find a root name server and get the
7898                         most recent
7899                         list of root name servers. If no hint zone is
7900                         specified for class
7901                         IN, the server uses a compiled-in default set of root
7902                         servers hints.
7903                         Classes other than IN have no built-in defaults hints.
7904                       </p>
7905                     </td>
7906 </tr>
7907 <tr>
7908 <td>
7909                       <p>
7910                         <code class="varname">redirect</code>
7911                       </p>
7912                     </td>
7913 <td>
7914                       <p>
7915                         Redirect zones are used to provide answers to
7916                         queries when normal resolution would result in
7917                         NXDOMAIN being returned.
7918                         Only one redirect zone is supported
7919                         per view.  <span><strong class="command">allow-query</strong></span> can be
7920                         used to restrict which clients see these answers.
7921                       </p>
7922                       <p>
7923                         If the client has requested DNSSEC records (DO=1) and
7924                         the NXDOMAIN response is signed then no substitution
7925                         will occur.
7926                       </p>
7927                       <p>
7928                         To redirect all NXDOMAIN responses to
7929                         100.100.100.2 and
7930                         2001:ffff:ffff::100.100.100.2, one would
7931                         configure a type redirect zone named ".",
7932                         with the zone file containing wildcard records
7933                         that point to the desired addresses:
7934                         <code class="literal">"*. IN A 100.100.100.2"</code>
7935                         and
7936                         <code class="literal">"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</code>.
7937                       </p>
7938                       <p>
7939                         To redirect all Spanish names (under .ES) one
7940                         would use similar entries but with the names
7941                         "*.ES." instead of "*.".  To redirect all
7942                         commercial Spanish names (under COM.ES) one
7943                         would use wildcard entries called "*.COM.ES.".
7944                       </p>
7945                       <p>
7946                         Note that the redirect zone supports all
7947                         possible types; it is not limited to A and
7948                         AAAA records.
7949                       </p>
7950                       <p>
7951                         Because redirect zones are not referenced
7952                         directly by name, they are not kept in the
7953                         zone lookup table with normal master and slave
7954                         zones. Consequently, it is not currently possible
7955                         to use
7956                         <span><strong class="command">rndc reload
7957                                 <em class="replaceable"><code>zonename</code></em></strong></span>
7958                         to reload a redirect zone.  However, when using
7959                         <span><strong class="command">rndc reload</strong></span> without specifying
7960                         a zone name, redirect zones will be reloaded along
7961                         with other zones.
7962                       </p>
7963                     </td>
7964 </tr>
7965 <tr>
7966 <td>
7967                       <p>
7968                         <code class="varname">delegation-only</code>
7969                       </p>
7970                     </td>
7971 <td>
7972                       <p>
7973                         This is used to enforce the delegation-only
7974                         status of infrastructure zones (e.g. COM,
7975                         NET, ORG).  Any answer that is received
7976                         without an explicit or implicit delegation
7977                         in the authority section will be treated
7978                         as NXDOMAIN.  This does not apply to the
7979                         zone apex.  This should not be applied to
7980                         leaf zones.
7981                       </p>
7982                       <p>
7983                         <code class="varname">delegation-only</code> has no
7984                         effect on answers received from forwarders.
7985                       </p>
7986                       <p>
7987                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
7988                       </p>
7989                     </td>
7990 </tr>
7991 </tbody>
7992 </table></div>
7993 </div>
7994 <div class="sect3" lang="en">
7995 <div class="titlepage"><div><div><h4 class="title">
7996 <a name="id2595218"></a>Class</h4></div></div></div>
7997 <p>
7998               The zone's name may optionally be followed by a class. If
7999               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
8000               is assumed. This is correct for the vast majority of cases.
8001             </p>
8002 <p>
8003               The <code class="literal">hesiod</code> class is
8004               named for an information service from MIT's Project Athena. It
8005               is
8006               used to share information about various systems databases, such
8007               as users, groups, printers and so on. The keyword
8008               <code class="literal">HS</code> is
8009               a synonym for hesiod.
8010             </p>
8011 <p>
8012               Another MIT development is Chaosnet, a LAN protocol created
8013               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
8014             </p>
8015 </div>
8016 <div class="sect3" lang="en">
8017 <div class="titlepage"><div><div><h4 class="title">
8018 <a name="id2595456"></a>Zone Options</h4></div></div></div>
8019 <div class="variablelist"><dl>
8020 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
8021 <dd><p>
8022                     See the description of
8023                     <span><strong class="command">allow-notify</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8024                   </p></dd>
8025 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
8026 <dd><p>
8027                     See the description of
8028                     <span><strong class="command">allow-query</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8029                   </p></dd>
8030 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
8031 <dd><p>
8032                     See the description of
8033                     <span><strong class="command">allow-query-on</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8034                   </p></dd>
8035 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
8036 <dd><p>
8037                     See the description of <span><strong class="command">allow-transfer</strong></span>
8038                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8039                   </p></dd>
8040 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
8041 <dd><p>
8042                     See the description of <span><strong class="command">allow-update</strong></span>
8043                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8044                   </p></dd>
8045 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
8046 <dd><p>
8047                     Specifies a "Simple Secure Update" policy. See
8048                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
8049                   </p></dd>
8050 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
8051 <dd><p>
8052                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
8053                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
8054                   </p></dd>
8055 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
8056 <dd><p>
8057                     Only meaningful if <span><strong class="command">notify</strong></span>
8058                     is
8059                     active for this zone. The set of machines that will
8060                     receive a
8061                     <code class="literal">DNS NOTIFY</code> message
8062                     for this zone is made up of all the listed name servers
8063                     (other than
8064                     the primary master) for the zone plus any IP addresses
8065                     specified
8066                     with <span><strong class="command">also-notify</strong></span>. A port
8067                     may be specified
8068                     with each <span><strong class="command">also-notify</strong></span>
8069                     address to send the notify
8070                     messages to a port other than the default of 53.
8071                     A TSIG key may also be specified to cause the
8072                     <code class="literal">NOTIFY</code> to be signed by the
8073                     given key.
8074                     <span><strong class="command">also-notify</strong></span> is not
8075                     meaningful for stub zones.
8076                     The default is the empty list.
8077                   </p></dd>
8078 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
8079 <dd><p>
8080                     This option is used to restrict the character set and
8081                     syntax of
8082                     certain domain names in master files and/or DNS responses
8083                     received from the
8084                     network.  The default varies according to zone type.  For <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.  For <span><strong class="command">slave</strong></span>
8085                     zones the default is <span><strong class="command">warn</strong></span>.
8086                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
8087                   </p></dd>
8088 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
8089 <dd><p>
8090                     See the description of
8091                     <span><strong class="command">check-mx</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8092                   </p></dd>
8093 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
8094 <dd><p>
8095                     See the description of
8096                     <span><strong class="command">check-spf</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8097                   </p></dd>
8098 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
8099 <dd><p>
8100                     See the description of
8101                     <span><strong class="command">check-wildcard</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8102                   </p></dd>
8103 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
8104 <dd><p>
8105                     See the description of
8106                     <span><strong class="command">check-integrity</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8107                   </p></dd>
8108 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
8109 <dd><p>
8110                     See the description of
8111                     <span><strong class="command">check-sibling</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8112                   </p></dd>
8113 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
8114 <dd><p>
8115                     See the description of
8116                     <span><strong class="command">zero-no-soa-ttl</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8117                   </p></dd>
8118 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
8119 <dd><p>
8120                     See the description of
8121                     <span><strong class="command">update-check-ksk</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8122                   </p></dd>
8123 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
8124 <dd><p>
8125                     See the description of
8126                     <span><strong class="command">dnssec-update-mode</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
8127           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
8128           Usage&#8221;</a>.
8129                   </p></dd>
8130 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
8131 <dd><p>
8132                     See the description of
8133                     <span><strong class="command">dnssec-dnskey-kskonly</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8134                   </p></dd>
8135 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
8136 <dd><p>
8137                     See the description of
8138                     <span><strong class="command">try-tcp-refresh</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8139                   </p></dd>
8140 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
8141 <dd>
8142 <p>
8143                     Specify the type of database to be used for storing the
8144                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
8145                     is interpreted as a list of whitespace-delimited words.
8146                     The first word
8147                     identifies the database type, and any subsequent words are
8148                     passed
8149                     as arguments to the database to be interpreted in a way
8150                     specific
8151                     to the database type.
8152                   </p>
8153 <p>
8154                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
8155                     native in-memory
8156                     red-black-tree database.  This database does not take
8157                     arguments.
8158                   </p>
8159 <p>
8160                     Other values are possible if additional database drivers
8161                     have been linked into the server.  Some sample drivers are
8162                     included
8163                     with the distribution but none are linked in by default.
8164                   </p>
8165 </dd>
8166 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
8167 <dd><p>
8168                     See the description of
8169                     <span><strong class="command">dialup</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8170                   </p></dd>
8171 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
8172 <dd>
8173 <p>
8174                     The flag only applies to forward, hint and stub
8175                     zones.  If set to <strong class="userinput"><code>yes</code></strong>,
8176                     then the zone will also be treated as if it is
8177                     also a delegation-only type zone.
8178                   </p>
8179 <p>
8180                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
8181                   </p>
8182 </dd>
8183 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
8184 <dd><p>
8185                     Only meaningful if the zone has a forwarders
8186                     list. The <span><strong class="command">only</strong></span> value causes
8187                     the lookup to fail
8188                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
8189                     allow a normal lookup to be tried.
8190                   </p></dd>
8191 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
8192 <dd><p>
8193                     Used to override the list of global forwarders.
8194                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
8195                     no forwarding is done for the zone and the global options are
8196                     not used.
8197                   </p></dd>
8198 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
8199 <dd><p>
8200                     Was used in <acronym class="acronym">BIND</acronym> 8 to
8201                     specify the name
8202                     of the transaction log (journal) file for dynamic update
8203                     and IXFR.
8204                     <acronym class="acronym">BIND</acronym> 9 ignores the option
8205                     and constructs the name of the journal
8206                     file by appending "<code class="filename">.jnl</code>"
8207                     to the name of the
8208                     zone file.
8209                   </p></dd>
8210 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
8211 <dd><p>
8212                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
8213                     Ignored in <acronym class="acronym">BIND</acronym> 9.
8214                   </p></dd>
8215 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
8216 <dd><p>
8217                     Allow the default journal's filename to be overridden.
8218                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
8219                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
8220                   </p></dd>
8221 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
8222 <dd><p>
8223                     See the description of
8224                     <span><strong class="command">max-journal-size</strong></span> in <a href="Bv9ARM.ch06.html#server_resource_limits" title="Server  Resource Limits">the section called &#8220;Server  Resource Limits&#8221;</a>.
8225                   </p></dd>
8226 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
8227 <dd><p>
8228                     See the description of
8229                     <span><strong class="command">max-transfer-time-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8230                   </p></dd>
8231 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
8232 <dd><p>
8233                     See the description of
8234                     <span><strong class="command">max-transfer-idle-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8235                   </p></dd>
8236 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
8237 <dd><p>
8238                     See the description of
8239                     <span><strong class="command">max-transfer-time-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8240                   </p></dd>
8241 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
8242 <dd><p>
8243                     See the description of
8244                     <span><strong class="command">max-transfer-idle-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8245                   </p></dd>
8246 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
8247 <dd><p>
8248                     See the description of
8249                     <span><strong class="command">notify</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8250                   </p></dd>
8251 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
8252 <dd><p>
8253                     See the description of
8254                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8255                   </p></dd>
8256 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
8257 <dd><p>
8258                     See the description of
8259                     <span><strong class="command">notify-to-soa</strong></span> in
8260                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8261                   </p></dd>
8262 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
8263 <dd><p>
8264                     In <acronym class="acronym">BIND</acronym> 8, this option was
8265                     intended for specifying
8266                     a public zone key for verification of signatures in DNSSEC
8267                     signed
8268                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
8269                     on load and ignores the option.
8270                   </p></dd>
8271 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
8272 <dd><p>
8273                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
8274                     statistical
8275                     information for this zone, which can be dumped to the
8276                     <span><strong class="command">statistics-file</strong></span> defined in
8277                     the server options.
8278                   </p></dd>
8279 <dt><span class="term"><span><strong class="command">server-addresses</strong></span></span></dt>
8280 <dd>
8281 <p>
8282                     Only meaningful for static-stub zones.
8283                     This is a list of IP addresses to which queries
8284                     should be sent in recursive resolution for the
8285                     zone.
8286                     A non empty list for this option will internally
8287                     configure the apex NS RR with associated glue A or
8288                     AAAA RRs.
8289                   </p>
8290 <p>
8291                     For example, if "example.com" is configured as a
8292                     static-stub zone with 192.0.2.1 and 2001:db8::1234
8293                     in a <span><strong class="command">server-addresses</strong></span> option,
8294                     the following RRs will be internally configured.
8295                   </p>
8296 <pre class="programlisting">example.com. NS example.com.
8297 example.com. A 192.0.2.1
8298 example.com. AAAA 2001:db8::1234</pre>
8299 <p>
8300                     These records are internally used to resolve
8301                     names under the static-stub zone.
8302                     For instance, if the server receives a query for
8303                     "www.example.com" with the RD bit on, the server
8304                     will initiate recursive resolution and send
8305                     queries to 192.0.2.1 and/or 2001:db8::1234.
8306                   </p>
8307 </dd>
8308 <dt><span class="term"><span><strong class="command">server-names</strong></span></span></dt>
8309 <dd>
8310 <p>
8311                     Only meaningful for static-stub zones.
8312                     This is a list of domain names of nameservers that
8313                     act as authoritative servers of the static-stub
8314                     zone.
8315                     These names will be resolved to IP addresses when
8316                     <span><strong class="command">named</strong></span> needs to send queries to
8317                     these servers.
8318                     To make this supplemental resolution successful,
8319                     these names must not be a subdomain of the origin
8320                     name of static-stub zone.
8321                     That is, when "example.net" is the origin of a
8322                     static-stub zone, "ns.example" and
8323                     "master.example.com" can be specified in the
8324                     <span><strong class="command">server-names</strong></span> option, but
8325                     "ns.example.net" cannot, and will be rejected by
8326                     the configuration parser.
8327                   </p>
8328 <p>
8329                     A non empty list for this option will internally
8330                     configure the apex NS RR with the specified names.
8331                     For example, if "example.com" is configured as a
8332                     static-stub zone with "ns1.example.net" and
8333                     "ns2.example.net"
8334                     in a <span><strong class="command">server-names</strong></span> option,
8335                     the following RRs will be internally configured.
8336                   </p>
8337 <pre class="programlisting">example.com. NS ns1.example.net.
8338 example.com. NS ns2.example.net.
8339 </pre>
8340 <p>
8341                     These records are internally used to resolve
8342                     names under the static-stub zone.
8343                     For instance, if the server receives a query for
8344                     "www.example.com" with the RD bit on, the server
8345                     initiate recursive resolution,
8346                     resolve "ns1.example.net" and/or
8347                     "ns2.example.net" to IP addresses, and then send
8348                     queries to (one or more of) these addresses.
8349                   </p>
8350 </dd>
8351 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
8352 <dd><p>
8353                     See the description of
8354                     <span><strong class="command">sig-validity-interval</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8355                   </p></dd>
8356 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
8357 <dd><p>
8358                     See the description of
8359                     <span><strong class="command">sig-signing-nodes</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8360                   </p></dd>
8361 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
8362 <dd><p>
8363                     See the description of
8364                     <span><strong class="command">sig-signing-signatures</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8365                   </p></dd>
8366 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
8367 <dd><p>
8368                     See the description of
8369                     <span><strong class="command">sig-signing-type</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8370                   </p></dd>
8371 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
8372 <dd><p>
8373                     See the description of
8374                     <span><strong class="command">transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8375                   </p></dd>
8376 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
8377 <dd><p>
8378                     See the description of
8379                     <span><strong class="command">transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8380                   </p></dd>
8381 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
8382 <dd><p>
8383                     See the description of
8384                     <span><strong class="command">alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8385                   </p></dd>
8386 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
8387 <dd><p>
8388                     See the description of
8389                     <span><strong class="command">alt-transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8390                   </p></dd>
8391 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
8392 <dd><p>
8393                     See the description of
8394                     <span><strong class="command">use-alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8395                   </p></dd>
8396 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
8397 <dd><p>
8398                     See the description of
8399                     <span><strong class="command">notify-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8400                   </p></dd>
8401 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
8402 <dd><p>
8403                     See the description of
8404                     <span><strong class="command">notify-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8405                   </p></dd>
8406 <dt>
8407 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
8408 </dt>
8409 <dd><p>
8410                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8411                   </p></dd>
8412 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
8413 <dd><p>
8414                     See the description of
8415                     <span><strong class="command">ixfr-from-differences</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8416                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
8417                     <strong class="userinput"><code>master</code></strong> and
8418                     <strong class="userinput"><code>slave</code></strong> choices are not
8419                     available at the zone level.)
8420                   </p></dd>
8421 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
8422 <dd><p>
8423                     See the description of
8424                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
8425           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
8426           Usage&#8221;</a>.
8427                   </p></dd>
8428 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
8429 <dd>
8430 <p>
8431                     Zones configured for dynamic DNS may also use this
8432                     option to allow varying levels of automatic DNSSEC key
8433                     management. There are three possible settings:
8434                   </p>
8435 <p>
8436                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
8437                     keys to be updated and the zone fully re-signed
8438                     whenever the user issues the command <span><strong class="command">rndc sign
8439                     <em class="replaceable"><code>zonename</code></em></strong></span>.
8440                   </p>
8441 <p>
8442                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
8443                     above, but also automatically adjusts the zone's DNSSEC
8444                     keys on schedule, according to the keys' timing metadata
8445                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
8446                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
8447                     <span><strong class="command">rndc sign
8448                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
8449                     <span><strong class="command">named</strong></span> to load keys from the key
8450                     repository and sign the zone with all keys that are
8451                     active.
8452                     <span><strong class="command">rndc loadkeys
8453                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
8454                     <span><strong class="command">named</strong></span> to load keys from the key
8455                     repository and schedule key maintenance events to occur
8456                     in the future, but it does not sign the full zone
8457                     immediately.  Note: once keys have been loaded for a
8458                     zone the first time, the repository will be searched
8459                     for changes periodically, regardless of whether
8460                     <span><strong class="command">rndc loadkeys</strong></span> is used.  The recheck
8461                     interval is defined by
8462                     <span><strong class="command">dnssec-loadkeys-interval</strong></span>.)
8463                   </p>
8464 <p>
8465                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
8466                   </p>
8467 </dd>
8468 <dt><span class="term"><span><strong class="command">serial-update-method</strong></span></span></dt>
8469 <dd>
8470 <p>
8471                     Zones configured for dynamic DNS may use this
8472                     option to set the update method that will be used for
8473                     the zone serial number in the SOA record.
8474                   </p>
8475 <p>
8476                     With the default setting of
8477                     <span><strong class="command">serial-update-method increment;</strong></span>, the
8478                     SOA serial number will be incremented by one each time
8479                     the zone is updated.
8480                   </p>
8481 <p>
8482                     When set to
8483                     <span><strong class="command">serial-update-method unixtime;</strong></span>, the
8484                     SOA serial number will be set to the number of seconds
8485                     since the UNIX epoch, unless the serial number is
8486                     already greater than or equal to that value, in which
8487                     case it is simply incremented by one.
8488                   </p>
8489 </dd>
8490 <dt><span class="term"><span><strong class="command">inline-signing</strong></span></span></dt>
8491 <dd><p>
8492                     If <code class="literal">yes</code>, this enables
8493                     "bump in the wire" signing of a zone, where a
8494                     unsigned zone is transferred in or loaded from
8495                     disk and a signed version of the zone is served,
8496                     with possibly, a different serial number.  This
8497                     behaviour is disabled by default.
8498                   </p></dd>
8499 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
8500 <dd><p>
8501                     See the description of <span><strong class="command">multi-master</strong></span> in
8502                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8503                   </p></dd>
8504 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
8505 <dd><p>
8506                     See the description of <span><strong class="command">masterfile-format</strong></span>
8507                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8508                   </p></dd>
8509 <dt><span class="term"><span><strong class="command">max-zone-ttl</strong></span></span></dt>
8510 <dd><p>
8511                     See the description of <span><strong class="command">max-zone-ttl</strong></span>
8512                     in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
8513           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
8514           Usage&#8221;</a>.
8515                   </p></dd>
8516 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
8517 <dd><p>
8518                     See the description of
8519                     <span><strong class="command">dnssec-secure-to-insecure</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8520                   </p></dd>
8521 </dl></div>
8522 </div>
8523 <div class="sect3" lang="en">
8524 <div class="titlepage"><div><div><h4 class="title">
8525 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
8526 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
8527               methods of granting clients the right to perform
8528               dynamic updates to a zone, configured by the
8529               <span><strong class="command">allow-update</strong></span> and
8530               <span><strong class="command">update-policy</strong></span> option, respectively.
8531             </p>
8532 <p>
8533               The <span><strong class="command">allow-update</strong></span> clause works the
8534               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
8535               It grants given clients the permission to update any
8536               record of any name in the zone.
8537             </p>
8538 <p>
8539               The <span><strong class="command">update-policy</strong></span> clause
8540               allows more fine-grained control over what updates are
8541               allowed.  A set of rules is specified, where each rule
8542               either grants or denies permissions for one or more
8543               names to be updated by one or more identities.  If
8544               the dynamic update request message is signed (that is,
8545               it includes either a TSIG or SIG(0) record), the
8546               identity of the signer can be determined.
8547             </p>
8548 <p>
8549               Rules are specified in the <span><strong class="command">update-policy</strong></span>
8550               zone option, and are only meaningful for master zones.
8551               When the <span><strong class="command">update-policy</strong></span> statement
8552               is present, it is a configuration error for the
8553               <span><strong class="command">allow-update</strong></span> statement to be
8554               present.  The <span><strong class="command">update-policy</strong></span> statement
8555               only examines the signer of a message; the source
8556               address is not relevant.
8557             </p>
8558 <p>
8559               There is a pre-defined <span><strong class="command">update-policy</strong></span>
8560               rule which can be switched on with the command
8561               <span><strong class="command">update-policy local;</strong></span>.
8562               Switching on this rule in a zone causes
8563               <span><strong class="command">named</strong></span> to generate a TSIG session
8564               key and place it in a file, and to allow that key
8565               to update the zone.  (By default, the file is
8566               <code class="filename">/var/run/named/session.key</code>, the key
8567               name is "local-ddns" and the key algorithm is HMAC-SHA256,
8568               but these values are configurable with the
8569               <span><strong class="command">session-keyfile</strong></span>,
8570               <span><strong class="command">session-keyname</strong></span> and
8571               <span><strong class="command">session-keyalg</strong></span> options, respectively).
8572             </p>
8573 <p>
8574               A client running on the local system, and with appropriate
8575               permissions, may read that file and use the key to sign update
8576               requests.  The zone's update policy will be set to allow that
8577               key to change any record within the zone.  Assuming the
8578               key name is "local-ddns", this policy is equivalent to:
8579             </p>
8580 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
8581             </pre>
8582 <p>
8583               The command <span><strong class="command">nsupdate -l</strong></span> sends update
8584               requests to localhost, and signs them using the session key.
8585             </p>
8586 <p>
8587               Other rule definitions look like this:
8588             </p>
8589 <pre class="programlisting">
8590 ( <span><strong class="command">grant</strong></span> | <span><strong class="command">deny</strong></span> ) <em class="replaceable"><code>identity</code></em> <em class="replaceable"><code>nametype</code></em> [<span class="optional"> <em class="replaceable"><code>name</code></em> </span>] [<span class="optional"> <em class="replaceable"><code>types</code></em> </span>]
8591 </pre>
8592 <p>
8593               Each rule grants or denies privileges.  Once a message has
8594               successfully matched a rule, the operation is immediately
8595               granted or denied and no further rules are examined.  A rule
8596               is matched when the signer matches the identity field, the
8597               name matches the name field in accordance with the nametype
8598               field, and the type matches the types specified in the type
8599               field.
8600             </p>
8601 <p>
8602               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
8603               or <em class="replaceable"><code>6to4-self</code></em> however the standard
8604               reverse mapping / prefix conversion must match the identity
8605               field.
8606             </p>
8607 <p>
8608               The identity field specifies a name or a wildcard
8609               name.  Normally, this is the name of the TSIG or
8610               SIG(0) key used to sign the update request.  When a
8611               TKEY exchange has been used to create a shared secret,
8612               the identity of the shared secret is the same as the
8613               identity of the key used to authenticate the TKEY
8614               exchange.  TKEY is also the negotiation method used
8615               by GSS-TSIG, which establishes an identity that is
8616               the Kerberos principal of the client, such as
8617               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
8618               <em class="replaceable"><code>identity</code></em> field specifies
8619               a wildcard name, it is subject to DNS wildcard
8620               expansion, so the rule will apply to multiple identities.
8621               The <em class="replaceable"><code>identity</code></em> field must
8622               contain a fully-qualified domain name.
8623             </p>
8624 <p>
8625               For nametypes <code class="varname">krb5-self</code>,
8626               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
8627               and <code class="varname">ms-subdomain</code> the
8628               <em class="replaceable"><code>identity</code></em> field specifies
8629               the Windows or Kerberos realm of the machine belongs to.
8630             </p>
8631 <p>
8632               The <em class="replaceable"><code>nametype</code></em> field has 13
8633               values:
8634               <code class="varname">name</code>, <code class="varname">subdomain</code>,
8635               <code class="varname">wildcard</code>, <code class="varname">self</code>,
8636               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
8637               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
8638               <code class="varname">krb5-subdomain</code>,
8639               <code class="varname">ms-subdomain</code>,
8640               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
8641               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
8642             </p>
8643 <div class="informaltable"><table border="1">
8644 <colgroup>
8645 <col>
8646 <col>
8647 </colgroup>
8648 <tbody>
8649 <tr>
8650 <td>
8651                       <p>
8652                         <code class="varname">name</code>
8653                       </p>
8654                     </td>
8655 <td>
8656                       <p>
8657                         Exact-match semantics.  This rule matches
8658                         when the name being updated is identical
8659                         to the contents of the
8660                         <em class="replaceable"><code>name</code></em> field.
8661                       </p>
8662                     </td>
8663 </tr>
8664 <tr>
8665 <td>
8666                       <p>
8667                         <code class="varname">subdomain</code>
8668                       </p>
8669                     </td>
8670 <td>
8671                       <p>
8672                         This rule matches when the name being updated
8673                         is a subdomain of, or identical to, the
8674                         contents of the <em class="replaceable"><code>name</code></em>
8675                         field.
8676                       </p>
8677                     </td>
8678 </tr>
8679 <tr>
8680 <td>
8681                       <p>
8682                         <code class="varname">zonesub</code>
8683                       </p>
8684                     </td>
8685 <td>
8686                       <p>
8687                         This rule is similar to subdomain, except that
8688                         it matches when the name being updated is a
8689                         subdomain of the zone in which the
8690                         <span><strong class="command">update-policy</strong></span> statement
8691                         appears.  This obviates the need to type the zone
8692                         name twice, and enables the use of a standard
8693                         <span><strong class="command">update-policy</strong></span> statement in
8694                         multiple zones without modification.
8695                       </p>
8696                       <p>
8697                         When this rule is used, the
8698                         <em class="replaceable"><code>name</code></em> field is omitted.
8699                       </p>
8700                     </td>
8701 </tr>
8702 <tr>
8703 <td>
8704                       <p>
8705                         <code class="varname">wildcard</code>
8706                       </p>
8707                     </td>
8708 <td>
8709                       <p>
8710                         The <em class="replaceable"><code>name</code></em> field
8711                         is subject to DNS wildcard expansion, and
8712                         this rule matches when the name being updated
8713                         name is a valid expansion of the wildcard.
8714                       </p>
8715                     </td>
8716 </tr>
8717 <tr>
8718 <td>
8719                       <p>
8720                         <code class="varname">self</code>
8721                       </p>
8722                     </td>
8723 <td>
8724                       <p>
8725                         This rule matches when the name being updated
8726                         matches the contents of the
8727                         <em class="replaceable"><code>identity</code></em> field.
8728                         The <em class="replaceable"><code>name</code></em> field
8729                         is ignored, but should be the same as the
8730                         <em class="replaceable"><code>identity</code></em> field.
8731                         The <code class="varname">self</code> nametype is
8732                         most useful when allowing using one key per
8733                         name to update, where the key has the same
8734                         name as the name to be updated.  The
8735                         <em class="replaceable"><code>identity</code></em> would
8736                         be specified as <code class="constant">*</code> (an asterisk) in
8737                         this case.
8738                       </p>
8739                     </td>
8740 </tr>
8741 <tr>
8742 <td>
8743                       <p>
8744                         <code class="varname">selfsub</code>
8745                       </p>
8746                     </td>
8747 <td>
8748                       <p>
8749                         This rule is similar to <code class="varname">self</code>
8750                         except that subdomains of <code class="varname">self</code>
8751                         can also be updated.
8752                       </p>
8753                     </td>
8754 </tr>
8755 <tr>
8756 <td>
8757                       <p>
8758                         <code class="varname">selfwild</code>
8759                       </p>
8760                     </td>
8761 <td>
8762                       <p>
8763                         This rule is similar to <code class="varname">self</code>
8764                         except that only subdomains of
8765                         <code class="varname">self</code> can be updated.
8766                       </p>
8767                     </td>
8768 </tr>
8769 <tr>
8770 <td>
8771                       <p>
8772                         <code class="varname">ms-self</code>
8773                       </p>
8774                     </td>
8775 <td>
8776                       <p>
8777                         This rule takes a Windows machine principal
8778                         (machine$@REALM) for machine in REALM and
8779                         and converts it machine.realm allowing the machine
8780                         to update machine.realm.  The REALM to be matched
8781                         is specified in the <em class="replaceable"><code>identity</code></em>
8782                         field.
8783                       </p>
8784                     </td>
8785 </tr>
8786 <tr>
8787 <td>
8788                       <p>
8789                         <code class="varname">ms-subdomain</code>
8790                       </p>
8791                     </td>
8792 <td>
8793                       <p>
8794                         This rule takes a Windows machine principal
8795                         (machine$@REALM) for machine in REALM and
8796                         converts it to machine.realm allowing the machine
8797                         to update subdomains of machine.realm.  The REALM
8798                         to be matched is specified in the
8799                         <em class="replaceable"><code>identity</code></em> field.
8800                       </p>
8801                     </td>
8802 </tr>
8803 <tr>
8804 <td>
8805                       <p>
8806                         <code class="varname">krb5-self</code>
8807                       </p>
8808                     </td>
8809 <td>
8810                       <p>
8811                         This rule takes a Kerberos machine principal
8812                         (host/machine@REALM) for machine in REALM and
8813                         and converts it machine.realm allowing the machine
8814                         to update machine.realm.  The REALM to be matched
8815                         is specified in the <em class="replaceable"><code>identity</code></em>
8816                         field.
8817                       </p>
8818                     </td>
8819 </tr>
8820 <tr>
8821 <td>
8822                       <p>
8823                         <code class="varname">krb5-subdomain</code>
8824                       </p>
8825                     </td>
8826 <td>
8827                       <p>
8828                         This rule takes a Kerberos machine principal
8829                         (host/machine@REALM) for machine in REALM and
8830                         converts it to machine.realm allowing the machine
8831                         to update subdomains of machine.realm.  The REALM
8832                         to be matched is specified in the
8833                         <em class="replaceable"><code>identity</code></em> field.
8834                       </p>
8835                     </td>
8836 </tr>
8837 <tr>
8838 <td>
8839                       <p>
8840                         <code class="varname">tcp-self</code>
8841                       </p>
8842                     </td>
8843 <td>
8844                       <p>
8845                         Allow updates that have been sent via TCP and
8846                         for which the standard mapping from the initiating
8847                         IP address into the IN-ADDR.ARPA and IP6.ARPA
8848                         namespaces match the name to be updated.
8849                       </p>
8850                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8851 <h3 class="title">Note</h3>
8852                         It is theoretically possible to spoof these TCP
8853                         sessions.
8854                       </div>
8855                     </td>
8856 </tr>
8857 <tr>
8858 <td>
8859                       <p>
8860                         <code class="varname">6to4-self</code>
8861                       </p>
8862                     </td>
8863 <td>
8864                       <p>
8865                         Allow the 6to4 prefix to be update by any TCP
8866                         connection from the 6to4 network or from the
8867                         corresponding IPv4 address.  This is intended
8868                         to allow NS or DNAME RRsets to be added to the
8869                         reverse tree.
8870                       </p>
8871                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8872 <h3 class="title">Note</h3>
8873                         It is theoretically possible to spoof these TCP
8874                         sessions.
8875                       </div>
8876                     </td>
8877 </tr>
8878 <tr>
8879 <td>
8880                       <p>
8881                         <code class="varname">external</code>
8882                       </p>
8883                     </td>
8884 <td>
8885                       <p>
8886                         This rule allows <span><strong class="command">named</strong></span>
8887                         to defer the decision of whether to allow a
8888                         given update to an external daemon.
8889                       </p>
8890                       <p>
8891                         The method of communicating with the daemon is
8892                         specified in the <em class="replaceable"><code>identity</code></em>
8893                         field, the format of which is
8894                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
8895                         where <em class="replaceable"><code>path</code></em> is the location
8896                         of a UNIX-domain socket.  (Currently, "local" is the
8897                         only supported mechanism.)
8898                       </p>
8899                       <p>
8900                         Requests to the external daemon are sent over the
8901                         UNIX-domain socket as datagrams with the following
8902                         format:
8903                       </p>
8904                       <pre class="programlisting">
8905    Protocol version number (4 bytes, network byte order, currently 1)
8906    Request length (4 bytes, network byte order)
8907    Signer (null-terminated string)
8908    Name (null-terminated string)
8909    TCP source address (null-terminated string)
8910    Rdata type (null-terminated string)
8911    Key (null-terminated string)
8912    TKEY token length (4 bytes, network byte order)
8913    TKEY token (remainder of packet)</pre>
8914                       <p>
8915                         The daemon replies with a four-byte value in
8916                         network byte order, containing either 0 or 1; 0
8917                         indicates that the specified update is not
8918                         permitted, and 1 indicates that it is.
8919                       </p>
8920                     </td>
8921 </tr>
8922 </tbody>
8923 </table></div>
8924 <p>
8925               In all cases, the <em class="replaceable"><code>name</code></em>
8926               field must specify a fully-qualified domain name.
8927             </p>
8928 <p>
8929               If no types are explicitly specified, this rule matches
8930               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
8931               may be specified by name, including "ANY" (ANY matches
8932               all types except NSEC and NSEC3, which can never be
8933               updated).  Note that when an attempt is made to delete
8934               all records associated with a name, the rules are
8935               checked for each existing record type.
8936             </p>
8937 </div>
8938 <div class="sect3" lang="en">
8939 <div class="titlepage"><div><div><h4 class="title">
8940 <a name="id2598241"></a>Multiple views</h4></div></div></div>
8941 <p>
8942               When multiple views are in use, a zone may be
8943               referenced by more than one of them. Often, the views
8944               will contain different zones with the same name, allowing
8945               different clients to receive different answers for the same
8946               queries. At times, however, it is desirable for multiple
8947               views to contain identical zones.  The
8948               <span><strong class="command">in-view</strong></span> zone option provides an efficient
8949               way to do this: it allows a view to reference a zone that
8950               was defined in a previously configured view. Example:
8951             </p>
8952 <pre class="programlisting">
8953 view internal {
8954     match-clients { 10/8; };
8955
8956     zone example.com {
8957         type master;
8958         file "example-external.db";
8959     };
8960 };
8961
8962 view external {
8963     match-clients { any; };
8964
8965     zone example.com {
8966         in-view internal;
8967     };
8968 };
8969             </pre>
8970 <p>
8971               An <span><strong class="command">in-view</strong></span> option cannot refer to a view
8972               that is configured later in the configuration file.
8973             </p>
8974 <p>
8975               A <span><strong class="command">zone</strong></span> statement which uses the
8976               <span><strong class="command">in-view</strong></span> option may not use any other
8977               options with the exception of <span><strong class="command">forward</strong></span>
8978               and <span><strong class="command">forwarders</strong></span>. (These options control
8979               the behavior of the containing view, rather than changing
8980               the zone object itself.)
8981             </p>
8982 <p>
8983               An <span><strong class="command">in-view</strong></span> zone cannot be used as a
8984               response policy zone.
8985             </p>
8986 </div>
8987 </div>
8988 </div>
8989 <div class="sect1" lang="en">
8990 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
8991 <a name="id2598289"></a>Zone File</h2></div></div></div>
8992 <div class="sect2" lang="en">
8993 <div class="titlepage"><div><div><h3 class="title">
8994 <a name="types_of_resource_records_and_when_to_use_them"></a>Types of Resource Records and When to Use Them</h3></div></div></div>
8995 <p>
8996             This section, largely borrowed from RFC 1034, describes the
8997             concept of a Resource Record (RR) and explains when each is used.
8998             Since the publication of RFC 1034, several new RRs have been
8999             identified
9000             and implemented in the DNS. These are also included.
9001           </p>
9002 <div class="sect3" lang="en">
9003 <div class="titlepage"><div><div><h4 class="title">
9004 <a name="id2598375"></a>Resource Records</h4></div></div></div>
9005 <p>
9006               A domain name identifies a node.  Each node has a set of
9007               resource information, which may be empty.  The set of resource
9008               information associated with a particular name is composed of
9009               separate RRs. The order of RRs in a set is not significant and
9010               need not be preserved by name servers, resolvers, or other
9011               parts of the DNS. However, sorting of multiple RRs is
9012               permitted for optimization purposes, for example, to specify
9013               that a particular nearby server be tried first. See <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a> and <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>.
9014             </p>
9015 <p>
9016               The components of a Resource Record are:
9017             </p>
9018 <div class="informaltable"><table border="1">
9019 <colgroup>
9020 <col>
9021 <col>
9022 </colgroup>
9023 <tbody>
9024 <tr>
9025 <td>
9026                       <p>
9027                         owner name
9028                       </p>
9029                     </td>
9030 <td>
9031                       <p>
9032                         The domain name where the RR is found.
9033                       </p>
9034                     </td>
9035 </tr>
9036 <tr>
9037 <td>
9038                       <p>
9039                         type
9040                       </p>
9041                     </td>
9042 <td>
9043                       <p>
9044                         An encoded 16-bit value that specifies
9045                         the type of the resource record.
9046                       </p>
9047                     </td>
9048 </tr>
9049 <tr>
9050 <td>
9051                       <p>
9052                         TTL
9053                       </p>
9054                     </td>
9055 <td>
9056                       <p>
9057                         The time-to-live of the RR. This field
9058                         is a 32-bit integer in units of seconds, and is
9059                         primarily used by
9060                         resolvers when they cache RRs. The TTL describes how
9061                         long a RR can
9062                         be cached before it should be discarded.
9063                       </p>
9064                     </td>
9065 </tr>
9066 <tr>
9067 <td>
9068                       <p>
9069                         class
9070                       </p>
9071                     </td>
9072 <td>
9073                       <p>
9074                         An encoded 16-bit value that identifies
9075                         a protocol family or instance of a protocol.
9076                       </p>
9077                     </td>
9078 </tr>
9079 <tr>
9080 <td>
9081                       <p>
9082                         RDATA
9083                       </p>
9084                     </td>
9085 <td>
9086                       <p>
9087                         The resource data.  The format of the
9088                         data is type (and sometimes class) specific.
9089                       </p>
9090                     </td>
9091 </tr>
9092 </tbody>
9093 </table></div>
9094 <p>
9095               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
9096             </p>
9097 <div class="informaltable"><table border="1">
9098 <colgroup>
9099 <col>
9100 <col>
9101 </colgroup>
9102 <tbody>
9103 <tr>
9104 <td>
9105                       <p>
9106                         A
9107                       </p>
9108                     </td>
9109 <td>
9110                       <p>
9111                         A host address.  In the IN class, this is a
9112                         32-bit IP address.  Described in RFC 1035.
9113                       </p>
9114                     </td>
9115 </tr>
9116 <tr>
9117 <td>
9118                       <p>
9119                         AAAA
9120                       </p>
9121                     </td>
9122 <td>
9123                       <p>
9124                         IPv6 address.  Described in RFC 1886.
9125                       </p>
9126                     </td>
9127 </tr>
9128 <tr>
9129 <td>
9130                       <p>
9131                         A6
9132                       </p>
9133                     </td>
9134 <td>
9135                       <p>
9136                         IPv6 address.  This can be a partial
9137                         address (a suffix) and an indirection to the name
9138                         where the rest of the
9139                         address (the prefix) can be found.  Experimental.
9140                         Described in RFC 2874.
9141                       </p>
9142                     </td>
9143 </tr>
9144 <tr>
9145 <td>
9146                       <p>
9147                         AFSDB
9148                       </p>
9149                     </td>
9150 <td>
9151                       <p>
9152                         Location of AFS database servers.
9153                         Experimental.  Described in RFC 1183.
9154                       </p>
9155                     </td>
9156 </tr>
9157 <tr>
9158 <td>
9159                       <p>
9160                         APL
9161                       </p>
9162                     </td>
9163 <td>
9164                       <p>
9165                         Address prefix list.  Experimental.
9166                         Described in RFC 3123.
9167                       </p>
9168                     </td>
9169 </tr>
9170 <tr>
9171 <td>
9172                       <p>
9173                         CERT
9174                       </p>
9175                     </td>
9176 <td>
9177                       <p>
9178                         Holds a digital certificate.
9179                         Described in RFC 2538.
9180                       </p>
9181                     </td>
9182 </tr>
9183 <tr>
9184 <td>
9185                       <p>
9186                         CNAME
9187                       </p>
9188                     </td>
9189 <td>
9190                       <p>
9191                         Identifies the canonical name of an alias.
9192                         Described in RFC 1035.
9193                       </p>
9194                     </td>
9195 </tr>
9196 <tr>
9197 <td>
9198                       <p>
9199                         DHCID
9200                       </p>
9201                     </td>
9202 <td>
9203                       <p>
9204                         Is used for identifying which DHCP client is
9205                         associated with this name.  Described in RFC 4701.
9206                       </p>
9207                     </td>
9208 </tr>
9209 <tr>
9210 <td>
9211                       <p>
9212                         DNAME
9213                       </p>
9214                     </td>
9215 <td>
9216                       <p>
9217                         Replaces the domain name specified with
9218                         another name to be looked up, effectively aliasing an
9219                         entire
9220                         subtree of the domain name space rather than a single
9221                         record
9222                         as in the case of the CNAME RR.
9223                         Described in RFC 2672.
9224                       </p>
9225                     </td>
9226 </tr>
9227 <tr>
9228 <td>
9229                       <p>
9230                         DNSKEY
9231                       </p>
9232                     </td>
9233 <td>
9234                       <p>
9235                         Stores a public key associated with a signed
9236                         DNS zone.  Described in RFC 4034.
9237                       </p>
9238                     </td>
9239 </tr>
9240 <tr>
9241 <td>
9242                       <p>
9243                         DS
9244                       </p>
9245                     </td>
9246 <td>
9247                       <p>
9248                         Stores the hash of a public key associated with a
9249                         signed DNS zone.  Described in RFC 4034.
9250                       </p>
9251                     </td>
9252 </tr>
9253 <tr>
9254 <td>
9255                       <p>
9256                         GPOS
9257                       </p>
9258                     </td>
9259 <td>
9260                       <p>
9261                         Specifies the global position.  Superseded by LOC.
9262                       </p>
9263                     </td>
9264 </tr>
9265 <tr>
9266 <td>
9267                       <p>
9268                         HINFO
9269                       </p>
9270                     </td>
9271 <td>
9272                       <p>
9273                         Identifies the CPU and OS used by a host.
9274                         Described in RFC 1035.
9275                       </p>
9276                     </td>
9277 </tr>
9278 <tr>
9279 <td>
9280                       <p>
9281                         IPSECKEY
9282                       </p>
9283                     </td>
9284 <td>
9285                       <p>
9286                         Provides a method for storing IPsec keying material in
9287                         DNS.  Described in RFC 4025.
9288                       </p>
9289                     </td>
9290 </tr>
9291 <tr>
9292 <td>
9293                       <p>
9294                         ISDN
9295                       </p>
9296                     </td>
9297 <td>
9298                       <p>
9299                         Representation of ISDN addresses.
9300                         Experimental.  Described in RFC 1183.
9301                       </p>
9302                     </td>
9303 </tr>
9304 <tr>
9305 <td>
9306                       <p>
9307                         KEY
9308                       </p>
9309                     </td>
9310 <td>
9311                       <p>
9312                         Stores a public key associated with a
9313                         DNS name.  Used in original DNSSEC; replaced
9314                         by DNSKEY in DNSSECbis, but still used with
9315                         SIG(0).  Described in RFCs 2535 and 2931.
9316                       </p>
9317                     </td>
9318 </tr>
9319 <tr>
9320 <td>
9321                       <p>
9322                         KX
9323                       </p>
9324                     </td>
9325 <td>
9326                       <p>
9327                         Identifies a key exchanger for this
9328                         DNS name.  Described in RFC 2230.
9329                       </p>
9330                     </td>
9331 </tr>
9332 <tr>
9333 <td>
9334                       <p>
9335                         LOC
9336                       </p>
9337                     </td>
9338 <td>
9339                       <p>
9340                         For storing GPS info.  Described in RFC 1876.
9341                         Experimental.
9342                       </p>
9343                     </td>
9344 </tr>
9345 <tr>
9346 <td>
9347                       <p>
9348                         MX
9349                       </p>
9350                     </td>
9351 <td>
9352                       <p>
9353                         Identifies a mail exchange for the domain with
9354                         a 16-bit preference value (lower is better)
9355                         followed by the host name of the mail exchange.
9356                         Described in RFC 974, RFC 1035.
9357                       </p>
9358                     </td>
9359 </tr>
9360 <tr>
9361 <td>
9362                       <p>
9363                         NAPTR
9364                       </p>
9365                     </td>
9366 <td>
9367                       <p>
9368                         Name authority pointer.  Described in RFC 2915.
9369                       </p>
9370                     </td>
9371 </tr>
9372 <tr>
9373 <td>
9374                       <p>
9375                         NSAP
9376                       </p>
9377                     </td>
9378 <td>
9379                       <p>
9380                         A network service access point.
9381                         Described in RFC 1706.
9382                       </p>
9383                     </td>
9384 </tr>
9385 <tr>
9386 <td>
9387                       <p>
9388                         NS
9389                       </p>
9390                     </td>
9391 <td>
9392                       <p>
9393                         The authoritative name server for the
9394                         domain.  Described in RFC 1035.
9395                       </p>
9396                     </td>
9397 </tr>
9398 <tr>
9399 <td>
9400                       <p>
9401                         NSEC
9402                       </p>
9403                     </td>
9404 <td>
9405                       <p>
9406                         Used in DNSSECbis to securely indicate that
9407                         RRs with an owner name in a certain name interval do
9408                         not exist in
9409                         a zone and indicate what RR types are present for an
9410                         existing name.
9411                         Described in RFC 4034.
9412                       </p>
9413                     </td>
9414 </tr>
9415 <tr>
9416 <td>
9417                       <p>
9418                         NSEC3
9419                       </p>
9420                     </td>
9421 <td>
9422                       <p>
9423                         Used in DNSSECbis to securely indicate that
9424                         RRs with an owner name in a certain name
9425                         interval do not exist in a zone and indicate
9426                         what RR types are present for an existing
9427                         name.  NSEC3 differs from NSEC in that it
9428                         prevents zone enumeration but is more
9429                         computationally expensive on both the server
9430                         and the client than NSEC.  Described in RFC
9431                         5155.
9432                       </p>
9433                     </td>
9434 </tr>
9435 <tr>
9436 <td>
9437                       <p>
9438                         NSEC3PARAM
9439                       </p>
9440                     </td>
9441 <td>
9442                       <p>
9443                         Used in DNSSECbis to tell the authoritative
9444                         server which NSEC3 chains are available to use.
9445                         Described in RFC 5155.
9446                       </p>
9447                     </td>
9448 </tr>
9449 <tr>
9450 <td>
9451                       <p>
9452                         NXT
9453                       </p>
9454                     </td>
9455 <td>
9456                       <p>
9457                         Used in DNSSEC to securely indicate that
9458                         RRs with an owner name in a certain name interval do
9459                         not exist in
9460                         a zone and indicate what RR types are present for an
9461                         existing name.
9462                         Used in original DNSSEC; replaced by NSEC in
9463                         DNSSECbis.
9464                         Described in RFC 2535.
9465                       </p>
9466                     </td>
9467 </tr>
9468 <tr>
9469 <td>
9470                       <p>
9471                         PTR
9472                       </p>
9473                     </td>
9474 <td>
9475                       <p>
9476                         A pointer to another part of the domain
9477                         name space.  Described in RFC 1035.
9478                       </p>
9479                     </td>
9480 </tr>
9481 <tr>
9482 <td>
9483                       <p>
9484                         PX
9485                       </p>
9486                     </td>
9487 <td>
9488                       <p>
9489                         Provides mappings between RFC 822 and X.400
9490                         addresses.  Described in RFC 2163.
9491                       </p>
9492                     </td>
9493 </tr>
9494 <tr>
9495 <td>
9496                       <p>
9497                         RP
9498                       </p>
9499                     </td>
9500 <td>
9501                       <p>
9502                         Information on persons responsible
9503                         for the domain.  Experimental.  Described in RFC 1183.
9504                       </p>
9505                     </td>
9506 </tr>
9507 <tr>
9508 <td>
9509                       <p>
9510                         RRSIG
9511                       </p>
9512                     </td>
9513 <td>
9514                       <p>
9515                         Contains DNSSECbis signature data.  Described
9516                         in RFC 4034.
9517                       </p>
9518                     </td>
9519 </tr>
9520 <tr>
9521 <td>
9522                       <p>
9523                         RT
9524                       </p>
9525                     </td>
9526 <td>
9527                       <p>
9528                         Route-through binding for hosts that
9529                         do not have their own direct wide area network
9530                         addresses.
9531                         Experimental.  Described in RFC 1183.
9532                       </p>
9533                     </td>
9534 </tr>
9535 <tr>
9536 <td>
9537                       <p>
9538                         SIG
9539                       </p>
9540                     </td>
9541 <td>
9542                       <p>
9543                         Contains DNSSEC signature data.  Used in
9544                         original DNSSEC; replaced by RRSIG in
9545                         DNSSECbis, but still used for SIG(0).
9546                         Described in RFCs 2535 and 2931.
9547                       </p>
9548                     </td>
9549 </tr>
9550 <tr>
9551 <td>
9552                       <p>
9553                         SOA
9554                       </p>
9555                     </td>
9556 <td>
9557                       <p>
9558                         Identifies the start of a zone of authority.
9559                         Described in RFC 1035.
9560                       </p>
9561                     </td>
9562 </tr>
9563 <tr>
9564 <td>
9565                       <p>
9566                         SPF
9567                       </p>
9568                     </td>
9569 <td>
9570                       <p>
9571                         Contains the Sender Policy Framework information
9572                         for a given email domain.  Described in RFC 4408.
9573                       </p>
9574                     </td>
9575 </tr>
9576 <tr>
9577 <td>
9578                       <p>
9579                         SRV
9580                       </p>
9581                     </td>
9582 <td>
9583                       <p>
9584                         Information about well known network
9585                         services (replaces WKS).  Described in RFC 2782.
9586                       </p>
9587                     </td>
9588 </tr>
9589 <tr>
9590 <td>
9591                       <p>
9592                         SSHFP
9593                       </p>
9594                     </td>
9595 <td>
9596                       <p>
9597                         Provides a way to securely publish a secure shell key's
9598                         fingerprint.  Described in RFC 4255.
9599                       </p>
9600                     </td>
9601 </tr>
9602 <tr>
9603 <td>
9604                       <p>
9605                         TXT
9606                       </p>
9607                     </td>
9608 <td>
9609                       <p>
9610                         Text records.  Described in RFC 1035.
9611                       </p>
9612                     </td>
9613 </tr>
9614 <tr>
9615 <td>
9616                       <p>
9617                         WKS
9618                       </p>
9619                     </td>
9620 <td>
9621                       <p>
9622                         Information about which well known
9623                         network services, such as SMTP, that a domain
9624                         supports. Historical.
9625                       </p>
9626                     </td>
9627 </tr>
9628 <tr>
9629 <td>
9630                       <p>
9631                         X25
9632                       </p>
9633                     </td>
9634 <td>
9635                       <p>
9636                         Representation of X.25 network addresses.
9637                         Experimental.  Described in RFC 1183.
9638                       </p>
9639                     </td>
9640 </tr>
9641 </tbody>
9642 </table></div>
9643 <p>
9644               The following <span class="emphasis"><em>classes</em></span> of resource records
9645               are currently valid in the DNS:
9646             </p>
9647 <div class="informaltable"><table border="1">
9648 <colgroup>
9649 <col>
9650 <col>
9651 </colgroup>
9652 <tbody>
9653 <tr>
9654 <td>
9655                       <p>
9656                         IN
9657                       </p>
9658                     </td>
9659 <td>
9660                       <p>
9661                         The Internet.
9662                       </p>
9663                     </td>
9664 </tr>
9665 <tr>
9666 <td>
9667                       <p>
9668                         CH
9669                       </p>
9670                     </td>
9671 <td>
9672                       <p>
9673                         Chaosnet, a LAN protocol created at MIT in the
9674                         mid-1970s.
9675                         Rarely used for its historical purpose, but reused for
9676                         BIND's
9677                         built-in server information zones, e.g.,
9678                         <code class="literal">version.bind</code>.
9679                       </p>
9680                     </td>
9681 </tr>
9682 <tr>
9683 <td>
9684                       <p>
9685                         HS
9686                       </p>
9687                     </td>
9688 <td>
9689                       <p>
9690                         Hesiod, an information service
9691                         developed by MIT's Project Athena. It is used to share
9692                         information
9693                         about various systems databases, such as users,
9694                         groups, printers
9695                         and so on.
9696                       </p>
9697                     </td>
9698 </tr>
9699 </tbody>
9700 </table></div>
9701 <p>
9702               The owner name is often implicit, rather than forming an
9703               integral
9704               part of the RR.  For example, many name servers internally form
9705               tree
9706               or hash structures for the name space, and chain RRs off nodes.
9707               The remaining RR parts are the fixed header (type, class, TTL)
9708               which is consistent for all RRs, and a variable part (RDATA)
9709               that
9710               fits the needs of the resource being described.
9711             </p>
9712 <p>
9713               The meaning of the TTL field is a time limit on how long an
9714               RR can be kept in a cache.  This limit does not apply to
9715               authoritative
9716               data in zones; it is also timed out, but by the refreshing
9717               policies
9718               for the zone.  The TTL is assigned by the administrator for the
9719               zone where the data originates.  While short TTLs can be used to
9720               minimize caching, and a zero TTL prohibits caching, the
9721               realities
9722               of Internet performance suggest that these times should be on
9723               the
9724               order of days for the typical host.  If a change can be
9725               anticipated,
9726               the TTL can be reduced prior to the change to minimize
9727               inconsistency
9728               during the change, and then increased back to its former value
9729               following
9730               the change.
9731             </p>
9732 <p>
9733               The data in the RDATA section of RRs is carried as a combination
9734               of binary strings and domain names.  The domain names are
9735               frequently
9736               used as "pointers" to other data in the DNS.
9737             </p>
9738 </div>
9739 <div class="sect3" lang="en">
9740 <div class="titlepage"><div><div><h4 class="title">
9741 <a name="id2599998"></a>Textual expression of RRs</h4></div></div></div>
9742 <p>
9743               RRs are represented in binary form in the packets of the DNS
9744               protocol, and are usually represented in highly encoded form
9745               when
9746               stored in a name server or resolver.  In the examples provided
9747               in
9748               RFC 1034, a style similar to that used in master files was
9749               employed
9750               in order to show the contents of RRs.  In this format, most RRs
9751               are shown on a single line, although continuation lines are
9752               possible
9753               using parentheses.
9754             </p>
9755 <p>
9756               The start of the line gives the owner of the RR.  If a line
9757               begins with a blank, then the owner is assumed to be the same as
9758               that of the previous RR.  Blank lines are often included for
9759               readability.
9760             </p>
9761 <p>
9762               Following the owner, we list the TTL, type, and class of the
9763               RR.  Class and type use the mnemonics defined above, and TTL is
9764               an integer before the type field.  In order to avoid ambiguity
9765               in
9766               parsing, type and class mnemonics are disjoint, TTLs are
9767               integers,
9768               and the type mnemonic is always last. The IN class and TTL
9769               values
9770               are often omitted from examples in the interests of clarity.
9771             </p>
9772 <p>
9773               The resource data or RDATA section of the RR are given using
9774               knowledge of the typical representation for the data.
9775             </p>
9776 <p>
9777               For example, we might show the RRs carried in a message as:
9778             </p>
9779 <div class="informaltable"><table border="1">
9780 <colgroup>
9781 <col>
9782 <col>
9783 <col>
9784 </colgroup>
9785 <tbody>
9786 <tr>
9787 <td>
9788                       <p>
9789                         <code class="literal">ISI.EDU.</code>
9790                       </p>
9791                     </td>
9792 <td>
9793                       <p>
9794                         <code class="literal">MX</code>
9795                       </p>
9796                     </td>
9797 <td>
9798                       <p>
9799                         <code class="literal">10 VENERA.ISI.EDU.</code>
9800                       </p>
9801                     </td>
9802 </tr>
9803 <tr>
9804 <td>
9805                       <p></p>
9806                     </td>
9807 <td>
9808                       <p>
9809                         <code class="literal">MX</code>
9810                       </p>
9811                     </td>
9812 <td>
9813                       <p>
9814                         <code class="literal">10 VAXA.ISI.EDU</code>
9815                       </p>
9816                     </td>
9817 </tr>
9818 <tr>
9819 <td>
9820                       <p>
9821                         <code class="literal">VENERA.ISI.EDU</code>
9822                       </p>
9823                     </td>
9824 <td>
9825                       <p>
9826                         <code class="literal">A</code>
9827                       </p>
9828                     </td>
9829 <td>
9830                       <p>
9831                         <code class="literal">128.9.0.32</code>
9832                       </p>
9833                     </td>
9834 </tr>
9835 <tr>
9836 <td>
9837                       <p></p>
9838                     </td>
9839 <td>
9840                       <p>
9841                         <code class="literal">A</code>
9842                       </p>
9843                     </td>
9844 <td>
9845                       <p>
9846                         <code class="literal">10.1.0.52</code>
9847                       </p>
9848                     </td>
9849 </tr>
9850 <tr>
9851 <td>
9852                       <p>
9853                         <code class="literal">VAXA.ISI.EDU</code>
9854                       </p>
9855                     </td>
9856 <td>
9857                       <p>
9858                         <code class="literal">A</code>
9859                       </p>
9860                     </td>
9861 <td>
9862                       <p>
9863                         <code class="literal">10.2.0.27</code>
9864                       </p>
9865                     </td>
9866 </tr>
9867 <tr>
9868 <td>
9869                       <p></p>
9870                     </td>
9871 <td>
9872                       <p>
9873                         <code class="literal">A</code>
9874                       </p>
9875                     </td>
9876 <td>
9877                       <p>
9878                         <code class="literal">128.9.0.33</code>
9879                       </p>
9880                     </td>
9881 </tr>
9882 </tbody>
9883 </table></div>
9884 <p>
9885               The MX RRs have an RDATA section which consists of a 16-bit
9886               number followed by a domain name.  The address RRs use a
9887               standard
9888               IP address format to contain a 32-bit internet address.
9889             </p>
9890 <p>
9891               The above example shows six RRs, with two RRs at each of three
9892               domain names.
9893             </p>
9894 <p>
9895               Similarly we might see:
9896             </p>
9897 <div class="informaltable"><table border="1">
9898 <colgroup>
9899 <col>
9900 <col>
9901 <col>
9902 </colgroup>
9903 <tbody>
9904 <tr>
9905 <td>
9906                       <p>
9907                         <code class="literal">XX.LCS.MIT.EDU.</code>
9908                       </p>
9909                     </td>
9910 <td>
9911                       <p>
9912                         <code class="literal">IN A</code>
9913                       </p>
9914                     </td>
9915 <td>
9916                       <p>
9917                         <code class="literal">10.0.0.44</code>
9918                       </p>
9919                     </td>
9920 </tr>
9921 <tr>
9922 <td> </td>
9923 <td>
9924                       <p>
9925                         <code class="literal">CH A</code>
9926                       </p>
9927                     </td>
9928 <td>
9929                       <p>
9930                         <code class="literal">MIT.EDU. 2420</code>
9931                       </p>
9932                     </td>
9933 </tr>
9934 </tbody>
9935 </table></div>
9936 <p>
9937               This example shows two addresses for
9938               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
9939             </p>
9940 </div>
9941 </div>
9942 <div class="sect2" lang="en">
9943 <div class="titlepage"><div><div><h3 class="title">
9944 <a name="id2600587"></a>Discussion of MX Records</h3></div></div></div>
9945 <p>
9946             As described above, domain servers store information as a
9947             series of resource records, each of which contains a particular
9948             piece of information about a given domain name (which is usually,
9949             but not always, a host). The simplest way to think of a RR is as
9950             a typed pair of data, a domain name matched with a relevant datum,
9951             and stored with some additional type information to help systems
9952             determine when the RR is relevant.
9953           </p>
9954 <p>
9955             MX records are used to control delivery of email. The data
9956             specified in the record is a priority and a domain name. The
9957             priority
9958             controls the order in which email delivery is attempted, with the
9959             lowest number first. If two priorities are the same, a server is
9960             chosen randomly. If no servers at a given priority are responding,
9961             the mail transport agent will fall back to the next largest
9962             priority.
9963             Priority numbers do not have any absolute meaning &#8212; they are
9964             relevant
9965             only respective to other MX records for that domain name. The
9966             domain
9967             name given is the machine to which the mail will be delivered.
9968             It <span class="emphasis"><em>must</em></span> have an associated address record
9969             (A or AAAA) &#8212; CNAME is not sufficient.
9970           </p>
9971 <p>
9972             For a given domain, if there is both a CNAME record and an
9973             MX record, the MX record is in error, and will be ignored.
9974             Instead,
9975             the mail will be delivered to the server specified in the MX
9976             record
9977             pointed to by the CNAME.
9978             For example:
9979           </p>
9980 <div class="informaltable"><table border="1">
9981 <colgroup>
9982 <col>
9983 <col>
9984 <col>
9985 <col>
9986 <col>
9987 </colgroup>
9988 <tbody>
9989 <tr>
9990 <td>
9991                     <p>
9992                       <code class="literal">example.com.</code>
9993                     </p>
9994                   </td>
9995 <td>
9996                     <p>
9997                       <code class="literal">IN</code>
9998                     </p>
9999                   </td>
10000 <td>
10001                     <p>
10002                       <code class="literal">MX</code>
10003                     </p>
10004                   </td>
10005 <td>
10006                     <p>
10007                       <code class="literal">10</code>
10008                     </p>
10009                   </td>
10010 <td>
10011                     <p>
10012                       <code class="literal">mail.example.com.</code>
10013                     </p>
10014                   </td>
10015 </tr>
10016 <tr>
10017 <td>
10018                     <p></p>
10019                   </td>
10020 <td>
10021                     <p>
10022                       <code class="literal">IN</code>
10023                     </p>
10024                   </td>
10025 <td>
10026                     <p>
10027                       <code class="literal">MX</code>
10028                     </p>
10029                   </td>
10030 <td>
10031                     <p>
10032                       <code class="literal">10</code>
10033                     </p>
10034                   </td>
10035 <td>
10036                     <p>
10037                       <code class="literal">mail2.example.com.</code>
10038                     </p>
10039                   </td>
10040 </tr>
10041 <tr>
10042 <td>
10043                     <p></p>
10044                   </td>
10045 <td>
10046                     <p>
10047                       <code class="literal">IN</code>
10048                     </p>
10049                   </td>
10050 <td>
10051                     <p>
10052                       <code class="literal">MX</code>
10053                     </p>
10054                   </td>
10055 <td>
10056                     <p>
10057                       <code class="literal">20</code>
10058                     </p>
10059                   </td>
10060 <td>
10061                     <p>
10062                       <code class="literal">mail.backup.org.</code>
10063                     </p>
10064                   </td>
10065 </tr>
10066 <tr>
10067 <td>
10068                     <p>
10069                       <code class="literal">mail.example.com.</code>
10070                     </p>
10071                   </td>
10072 <td>
10073                     <p>
10074                       <code class="literal">IN</code>
10075                     </p>
10076                   </td>
10077 <td>
10078                     <p>
10079                       <code class="literal">A</code>
10080                     </p>
10081                   </td>
10082 <td>
10083                     <p>
10084                       <code class="literal">10.0.0.1</code>
10085                     </p>
10086                   </td>
10087 <td>
10088                     <p></p>
10089                   </td>
10090 </tr>
10091 <tr>
10092 <td>
10093                     <p>
10094                       <code class="literal">mail2.example.com.</code>
10095                     </p>
10096                   </td>
10097 <td>
10098                     <p>
10099                       <code class="literal">IN</code>
10100                     </p>
10101                   </td>
10102 <td>
10103                     <p>
10104                       <code class="literal">A</code>
10105                     </p>
10106                   </td>
10107 <td>
10108                     <p>
10109                       <code class="literal">10.0.0.2</code>
10110                     </p>
10111                   </td>
10112 <td>
10113                     <p></p>
10114                   </td>
10115 </tr>
10116 </tbody>
10117 </table></div>
10118 <p>
10119             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
10120             <code class="literal">mail2.example.com</code> (in
10121             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
10122             be attempted.
10123           </p>
10124 </div>
10125 <div class="sect2" lang="en">
10126 <div class="titlepage"><div><div><h3 class="title">
10127 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
10128 <p>
10129             The time-to-live of the RR field is a 32-bit integer represented
10130             in units of seconds, and is primarily used by resolvers when they
10131             cache RRs. The TTL describes how long a RR can be cached before it
10132             should be discarded. The following three types of TTL are
10133             currently
10134             used in a zone file.
10135           </p>
10136 <div class="informaltable"><table border="1">
10137 <colgroup>
10138 <col>
10139 <col>
10140 </colgroup>
10141 <tbody>
10142 <tr>
10143 <td>
10144                     <p>
10145                       SOA
10146                     </p>
10147                   </td>
10148 <td>
10149                     <p>
10150                       The last field in the SOA is the negative
10151                       caching TTL. This controls how long other servers will
10152                       cache no-such-domain
10153                       (NXDOMAIN) responses from you.
10154                     </p>
10155                     <p>
10156                       The maximum time for
10157                       negative caching is 3 hours (3h).
10158                     </p>
10159                   </td>
10160 </tr>
10161 <tr>
10162 <td>
10163                     <p>
10164                       $TTL
10165                     </p>
10166                   </td>
10167 <td>
10168                     <p>
10169                       The $TTL directive at the top of the
10170                       zone file (before the SOA) gives a default TTL for every
10171                       RR without
10172                       a specific TTL set.
10173                     </p>
10174                   </td>
10175 </tr>
10176 <tr>
10177 <td>
10178                     <p>
10179                       RR TTLs
10180                     </p>
10181                   </td>
10182 <td>
10183                     <p>
10184                       Each RR can have a TTL as the second
10185                       field in the RR, which will control how long other
10186                       servers can cache it.
10187                     </p>
10188                   </td>
10189 </tr>
10190 </tbody>
10191 </table></div>
10192 <p>
10193             All of these TTLs default to units of seconds, though units
10194             can be explicitly specified, for example, <code class="literal">1h30m</code>.
10195           </p>
10196 </div>
10197 <div class="sect2" lang="en">
10198 <div class="titlepage"><div><div><h3 class="title">
10199 <a name="id2601134"></a>Inverse Mapping in IPv4</h3></div></div></div>
10200 <p>
10201             Reverse name resolution (that is, translation from IP address
10202             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
10203             and PTR records. Entries in the in-addr.arpa domain are made in
10204             least-to-most significant order, read left to right. This is the
10205             opposite order to the way IP addresses are usually written. Thus,
10206             a machine with an IP address of 10.1.2.3 would have a
10207             corresponding
10208             in-addr.arpa name of
10209             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
10210             whose data field is the name of the machine or, optionally,
10211             multiple
10212             PTR records if the machine has more than one name. For example,
10213             in the [<span class="optional">example.com</span>] domain:
10214           </p>
10215 <div class="informaltable"><table border="1">
10216 <colgroup>
10217 <col>
10218 <col>
10219 </colgroup>
10220 <tbody>
10221 <tr>
10222 <td>
10223                     <p>
10224                       <code class="literal">$ORIGIN</code>
10225                     </p>
10226                   </td>
10227 <td>
10228                     <p>
10229                       <code class="literal">2.1.10.in-addr.arpa</code>
10230                     </p>
10231                   </td>
10232 </tr>
10233 <tr>
10234 <td>
10235                     <p>
10236                       <code class="literal">3</code>
10237                     </p>
10238                   </td>
10239 <td>
10240                     <p>
10241                       <code class="literal">IN PTR foo.example.com.</code>
10242                     </p>
10243                   </td>
10244 </tr>
10245 </tbody>
10246 </table></div>
10247 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10248 <h3 class="title">Note</h3>
10249 <p>
10250               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
10251               are for providing context to the examples only &#8212; they do not
10252               necessarily
10253               appear in the actual usage. They are only used here to indicate
10254               that the example is relative to the listed origin.
10255             </p>
10256 </div>
10257 </div>
10258 <div class="sect2" lang="en">
10259 <div class="titlepage"><div><div><h3 class="title">
10260 <a name="id2601261"></a>Other Zone File Directives</h3></div></div></div>
10261 <p>
10262             The Master File Format was initially defined in RFC 1035 and
10263             has subsequently been extended. While the Master File Format
10264             itself
10265             is class independent all records in a Master File must be of the
10266             same
10267             class.
10268           </p>
10269 <p>
10270             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
10271             and <span><strong class="command">$TTL.</strong></span>
10272           </p>
10273 <div class="sect3" lang="en">
10274 <div class="titlepage"><div><div><h4 class="title">
10275 <a name="id2601284"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
10276 <p>
10277               When used in the label (or name) field, the asperand or
10278               at-sign (@) symbol represents the current origin.
10279               At the start of the zone file, it is the
10280               &lt;<code class="varname">zone_name</code>&gt; (followed by
10281               trailing dot).
10282             </p>
10283 </div>
10284 <div class="sect3" lang="en">
10285 <div class="titlepage"><div><div><h4 class="title">
10286 <a name="id2601300"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
10287 <p>
10288               Syntax: <span><strong class="command">$ORIGIN</strong></span>
10289               <em class="replaceable"><code>domain-name</code></em>
10290               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10291             </p>
10292 <p><span><strong class="command">$ORIGIN</strong></span>
10293               sets the domain name that will be appended to any
10294               unqualified records. When a zone is first read in there
10295               is an implicit <span><strong class="command">$ORIGIN</strong></span>
10296               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
10297               (followed by trailing dot).
10298               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
10299               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
10300               argument if it is not absolute.
10301             </p>
10302 <pre class="programlisting">
10303 $ORIGIN example.com.
10304 WWW     CNAME   MAIN-SERVER
10305 </pre>
10306 <p>
10307               is equivalent to
10308             </p>
10309 <pre class="programlisting">
10310 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
10311 </pre>
10312 </div>
10313 <div class="sect3" lang="en">
10314 <div class="titlepage"><div><div><h4 class="title">
10315 <a name="id2601429"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
10316 <p>
10317               Syntax: <span><strong class="command">$INCLUDE</strong></span>
10318               <em class="replaceable"><code>filename</code></em>
10319               [<span class="optional">
10320 <em class="replaceable"><code>origin</code></em> </span>]
10321               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
10322             </p>
10323 <p>
10324               Read and process the file <code class="filename">filename</code> as
10325               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
10326               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
10327               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
10328               used.
10329             </p>
10330 <p>
10331               The origin and the current domain name
10332               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
10333               the file has been read.
10334             </p>
10335 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10336 <h3 class="title">Note</h3>
10337 <p>
10338                 RFC 1035 specifies that the current origin should be restored
10339                 after
10340                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
10341                 on whether the current
10342                 domain name should also be restored.  BIND 9 restores both of
10343                 them.
10344                 This could be construed as a deviation from RFC 1035, a
10345                 feature, or both.
10346               </p>
10347 </div>
10348 </div>
10349 <div class="sect3" lang="en">
10350 <div class="titlepage"><div><div><h4 class="title">
10351 <a name="id2601498"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
10352 <p>
10353               Syntax: <span><strong class="command">$TTL</strong></span>
10354               <em class="replaceable"><code>default-ttl</code></em>
10355               [<span class="optional">
10356 <em class="replaceable"><code>comment</code></em> </span>]
10357             </p>
10358 <p>
10359               Set the default Time To Live (TTL) for subsequent records
10360               with undefined TTLs. Valid TTLs are of the range 0-2147483647
10361               seconds.
10362             </p>
10363 <p><span><strong class="command">$TTL</strong></span>
10364                is defined in RFC 2308.
10365             </p>
10366 </div>
10367 </div>
10368 <div class="sect2" lang="en">
10369 <div class="titlepage"><div><div><h3 class="title">
10370 <a name="id2601534"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
10371 <p>
10372             Syntax: <span><strong class="command">$GENERATE</strong></span>
10373             <em class="replaceable"><code>range</code></em>
10374             <em class="replaceable"><code>lhs</code></em>
10375             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
10376             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
10377             <em class="replaceable"><code>type</code></em>
10378             <em class="replaceable"><code>rhs</code></em>
10379             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10380           </p>
10381 <p><span><strong class="command">$GENERATE</strong></span>
10382             is used to create a series of resource records that only
10383             differ from each other by an
10384             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
10385             easily generate the sets of records required to support
10386             sub /24 reverse delegations described in RFC 2317:
10387             Classless IN-ADDR.ARPA delegation.
10388           </p>
10389 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
10390 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
10391 $GENERATE 1-127 $ CNAME $.0</pre>
10392 <p>
10393             is equivalent to
10394           </p>
10395 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
10396 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
10397 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
10398 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
10399 ...
10400 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
10401 </pre>
10402 <p>
10403             Generate a set of A and MX records.  Note the MX's right hand
10404             side is a quoted string.  The quotes will be stripped when the
10405             right hand side is processed.
10406            </p>
10407 <pre class="programlisting">
10408 $ORIGIN EXAMPLE.
10409 $GENERATE 1-127 HOST-$ A 1.2.3.$
10410 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
10411 <p>
10412             is equivalent to
10413           </p>
10414 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
10415 HOST-1.EXAMPLE.   MX 0 .
10416 HOST-2.EXAMPLE.   A  1.2.3.2
10417 HOST-2.EXAMPLE.   MX 0 .
10418 HOST-3.EXAMPLE.   A  1.2.3.3
10419 HOST-3.EXAMPLE.   MX 0 .
10420 ...
10421 HOST-127.EXAMPLE. A  1.2.3.127
10422 HOST-127.EXAMPLE. MX 0 .
10423 </pre>
10424 <div class="informaltable"><table border="1">
10425 <colgroup>
10426 <col>
10427 <col>
10428 </colgroup>
10429 <tbody>
10430 <tr>
10431 <td>
10432                     <p><span><strong class="command">range</strong></span></p>
10433                   </td>
10434 <td>
10435                     <p>
10436                       This can be one of two forms: start-stop
10437                       or start-stop/step. If the first form is used, then step
10438                       is set to 1. start, stop and step must be positive
10439                       integers between 0 and (2^31)-1. start must not be
10440                       larger than stop.
10441                     </p>
10442                   </td>
10443 </tr>
10444 <tr>
10445 <td>
10446                     <p><span><strong class="command">lhs</strong></span></p>
10447                   </td>
10448 <td>
10449                     <p>This
10450                       describes the owner name of the resource records
10451                       to be created.  Any single <span><strong class="command">$</strong></span>
10452                       (dollar sign)
10453                       symbols within the <span><strong class="command">lhs</strong></span> string
10454                       are replaced by the iterator value.
10455
10456                       To get a $ in the output, you need to escape the
10457                       <span><strong class="command">$</strong></span> using a backslash
10458                       <span><strong class="command">\</strong></span>,
10459                       e.g. <span><strong class="command">\$</strong></span>. The
10460                       <span><strong class="command">$</strong></span> may optionally be followed
10461                       by modifiers which change the offset from the
10462                       iterator, field width and base.
10463
10464                       Modifiers are introduced by a
10465                       <span><strong class="command">{</strong></span> (left brace) immediately following the
10466                       <span><strong class="command">$</strong></span> as
10467                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
10468                       For example, <span><strong class="command">${-20,3,d}</strong></span>
10469                       subtracts 20 from the current value, prints the
10470                       result as a decimal in a zero-padded field of
10471                       width 3.
10472
10473                       Available output forms are decimal
10474                       (<span><strong class="command">d</strong></span>), octal
10475                       (<span><strong class="command">o</strong></span>), hexadecimal
10476                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
10477                       for uppercase) and nibble
10478                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
10479                       for uppercase).  The default modifier is
10480                       <span><strong class="command">${0,0,d}</strong></span>.  If the
10481                       <span><strong class="command">lhs</strong></span> is not absolute, the
10482                       current <span><strong class="command">$ORIGIN</strong></span> is appended
10483                       to the name.
10484                     </p>
10485                     <p>
10486                       In nibble mode the value will be treated as
10487                       if it was a reversed hexadecimal string
10488                       with each hexadecimal digit as a separate
10489                       label.  The width field includes the label
10490                       separator.
10491                     </p>
10492                     <p>
10493                       For compatibility with earlier versions,
10494                       <span><strong class="command">$$</strong></span> is still recognized as
10495                       indicating a literal $ in the output.
10496                     </p>
10497                   </td>
10498 </tr>
10499 <tr>
10500 <td>
10501                     <p><span><strong class="command">ttl</strong></span></p>
10502                   </td>
10503 <td>
10504                     <p>
10505                       Specifies the time-to-live of the generated records. If
10506                       not specified this will be inherited using the
10507                       normal TTL inheritance rules.
10508                     </p>
10509                     <p><span><strong class="command">class</strong></span>
10510                       and <span><strong class="command">ttl</strong></span> can be
10511                       entered in either order.
10512                     </p>
10513                   </td>
10514 </tr>
10515 <tr>
10516 <td>
10517                     <p><span><strong class="command">class</strong></span></p>
10518                   </td>
10519 <td>
10520                     <p>
10521                       Specifies the class of the generated records.
10522                       This must match the zone class if it is
10523                       specified.
10524                     </p>
10525                     <p><span><strong class="command">class</strong></span>
10526                       and <span><strong class="command">ttl</strong></span> can be
10527                       entered in either order.
10528                     </p>
10529                   </td>
10530 </tr>
10531 <tr>
10532 <td>
10533                     <p><span><strong class="command">type</strong></span></p>
10534                   </td>
10535 <td>
10536                     <p>
10537                       Any valid type.
10538                     </p>
10539                   </td>
10540 </tr>
10541 <tr>
10542 <td>
10543                     <p><span><strong class="command">rhs</strong></span></p>
10544                   </td>
10545 <td>
10546                     <p>
10547                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
10548                     </p>
10549                   </td>
10550 </tr>
10551 </tbody>
10552 </table></div>
10553 <p>
10554             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
10555             and not part of the standard zone file format.
10556           </p>
10557 <p>
10558             BIND 8 does not support the optional TTL and CLASS fields.
10559           </p>
10560 </div>
10561 <div class="sect2" lang="en">
10562 <div class="titlepage"><div><div><h3 class="title">
10563 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
10564 <p>
10565             In addition to the standard textual format, BIND 9
10566             supports the ability to read or dump to zone files in
10567             other formats.
10568           </p>
10569 <p>
10570             The <code class="constant">raw</code> format is
10571             a binary representation of zone data in a manner similar
10572             to that used in zone transfers.  Since it does not require
10573             parsing text, load time is significantly reduced.
10574           </p>
10575 <p>
10576             An even faster alternative is the <code class="constant">map</code>
10577             format, which is an image of a <acronym class="acronym">BIND</acronym> 9
10578             in-memory zone database; it is capable of being loaded
10579             directly into memory via the <span><strong class="command">mmap()</strong></span>
10580             function; the zone can begin serving queries almost
10581             immediately.
10582           </p>
10583 <p>
10584             For a primary server, a zone file in
10585             <code class="constant">raw</code> or <code class="constant">map</code>
10586             format is expected to be generated from a textual zone
10587             file by the <span><strong class="command">named-compilezone</strong></span> command.
10588             For a secondary server or for a dynamic zone, it is automatically
10589             generated (if this format is specified by the
10590             <span><strong class="command">masterfile-format</strong></span> option) when
10591             <span><strong class="command">named</strong></span> dumps the zone contents after
10592             zone transfer or when applying prior updates.
10593           </p>
10594 <p>
10595             If a zone file in a binary format needs manual modification,
10596             it first must be converted to a textual form by the
10597             <span><strong class="command">named-compilezone</strong></span> command.  All
10598             necessary modification should go to the text file, which
10599             should then be converted to the binary form by the
10600             <span><strong class="command">named-compilezone</strong></span> command again.
10601           </p>
10602 <p>
10603             Note that <span><strong class="command">map</strong></span> format is extremely
10604             architecture-specific.  A <code class="constant">map</code>
10605             file <span class="emphasis"><em>cannot</em></span> be used on a system
10606             with different pointer size, endianness or data alignment
10607             than the system on which it was generated, and should in
10608             general be used only inside a single system.
10609             While <code class="constant">raw</code> format uses
10610             network byte order and avoids architecture-dependent
10611             data alignment so that it is as portable as
10612             possible, it is also primarily expected to be used
10613             inside the same single system.  To export a
10614             zone file in either <code class="constant">raw</code> or
10615             <code class="constant">map</code> format, or make a
10616             portable backup of such a file, conversion to
10617             <code class="constant">text</code> format is recommended.
10618           </p>
10619 </div>
10620 </div>
10621 <div class="sect1" lang="en">
10622 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
10623 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
10624 <p>
10625           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
10626           information and provides several interfaces for users to
10627           get access to the statistics.
10628           The available statistics include all statistics counters
10629           that were available in <acronym class="acronym">BIND</acronym> 8 and
10630           are meaningful in <acronym class="acronym">BIND</acronym> 9,
10631           and other information that is considered useful.
10632         </p>
10633 <p>
10634           The statistics information is categorized into the following
10635           sections.
10636         </p>
10637 <div class="informaltable"><table border="1">
10638 <colgroup>
10639 <col>
10640 <col>
10641 </colgroup>
10642 <tbody>
10643 <tr>
10644 <td>
10645                   <p>Incoming Requests</p>
10646                 </td>
10647 <td>
10648                   <p>
10649                     The number of incoming DNS requests for each OPCODE.
10650                   </p>
10651                 </td>
10652 </tr>
10653 <tr>
10654 <td>
10655                   <p>Incoming Queries</p>
10656                 </td>
10657 <td>
10658                   <p>
10659                     The number of incoming queries for each RR type.
10660                   </p>
10661                 </td>
10662 </tr>
10663 <tr>
10664 <td>
10665                   <p>Outgoing Queries</p>
10666                 </td>
10667 <td>
10668                   <p>
10669                     The number of outgoing queries for each RR
10670                     type sent from the internal resolver.
10671                     Maintained per view.
10672                   </p>
10673                 </td>
10674 </tr>
10675 <tr>
10676 <td>
10677                   <p>Name Server Statistics</p>
10678                 </td>
10679 <td>
10680                   <p>
10681                     Statistics counters about incoming request processing.
10682                   </p>
10683                 </td>
10684 </tr>
10685 <tr>
10686 <td>
10687                   <p>Zone Maintenance Statistics</p>
10688                 </td>
10689 <td>
10690                   <p>
10691                     Statistics counters regarding zone maintenance
10692                     operations such as zone transfers.
10693                   </p>
10694                 </td>
10695 </tr>
10696 <tr>
10697 <td>
10698                   <p>Resolver Statistics</p>
10699                 </td>
10700 <td>
10701                   <p>
10702                     Statistics counters about name resolution
10703                     performed in the internal resolver.
10704                     Maintained per view.
10705                   </p>
10706                 </td>
10707 </tr>
10708 <tr>
10709 <td>
10710                   <p>Cache DB RRsets</p>
10711                 </td>
10712 <td>
10713                   <p>
10714                     The number of RRsets per RR type and nonexistent
10715                     names stored in the cache database.
10716                     If the exclamation mark (!) is printed for a RR
10717                     type, it means that particular type of RRset is
10718                     known to be nonexistent (this is also known as
10719                     "NXRRSET").  If a hash mark (#) is present then
10720                     the RRset is marked for garbage collection.
10721                     Maintained per view.
10722                   </p>
10723                 </td>
10724 </tr>
10725 <tr>
10726 <td>
10727                   <p>Socket I/O Statistics</p>
10728                 </td>
10729 <td>
10730                   <p>
10731                     Statistics counters about network related events.
10732                   </p>
10733                 </td>
10734 </tr>
10735 </tbody>
10736 </table></div>
10737 <p>
10738           A subset of Name Server Statistics is collected and shown
10739           per zone for which the server has the authority when
10740           <span><strong class="command">zone-statistics</strong></span> is set to
10741           <strong class="userinput"><code>yes</code></strong>.
10742           These statistics counters are shown with their zone and view
10743           names.
10744           In some cases the view names are omitted for the default view.
10745         </p>
10746 <p>
10747           There are currently two user interfaces to get access to the
10748           statistics.
10749           One is in the plain text format dumped to the file specified
10750           by the <span><strong class="command">statistics-file</strong></span> configuration option.
10751           The other is remotely accessible via a statistics channel
10752           when the <span><strong class="command">statistics-channels</strong></span> statement
10753           is specified in the configuration file
10754           (see <a href="Bv9ARM.ch06.html#statschannels" title="statistics-channels Statement Grammar">the section called &#8220;<span><strong class="command">statistics-channels</strong></span> Statement Grammar&#8221;</a>.)
10755         </p>
10756 <div class="sect3" lang="en">
10757 <div class="titlepage"><div><div><h4 class="title">
10758 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
10759 <p>
10760             The text format statistics dump begins with a line, like:
10761           </p>
10762 <p>
10763             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
10764           </p>
10765 <p>
10766             The number in parentheses is a standard
10767             Unix-style timestamp, measured as seconds since January 1, 1970.
10768
10769             Following
10770             that line is a set of statistics information, which is categorized
10771             as described above.
10772             Each section begins with a line, like:
10773           </p>
10774 <p>
10775             <span><strong class="command">++ Name Server Statistics ++</strong></span>
10776           </p>
10777 <p>
10778             Each section consists of lines, each containing the statistics
10779             counter value followed by its textual description.
10780             See below for available counters.
10781             For brevity, counters that have a value of 0 are not shown
10782             in the statistics file.
10783           </p>
10784 <p>
10785             The statistics dump ends with the line where the
10786             number is identical to the number in the beginning line; for example:
10787           </p>
10788 <p>
10789             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
10790           </p>
10791 </div>
10792 <div class="sect2" lang="en">
10793 <div class="titlepage"><div><div><h3 class="title">
10794 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
10795 <p>
10796             The following tables summarize statistics counters that
10797             <acronym class="acronym">BIND</acronym> 9 provides.
10798             For each row of the tables, the leftmost column is the
10799             abbreviated symbol name of that counter.
10800             These symbols are shown in the statistics information
10801             accessed via an HTTP statistics channel.
10802             The rightmost column gives the description of the counter,
10803             which is also shown in the statistics file
10804             (but, in this document, possibly with slight modification
10805             for better readability).
10806             Additional notes may also be provided in this column.
10807             When a middle column exists between these two columns,
10808             it gives the corresponding counter name of the
10809             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
10810           </p>
10811 <div class="sect3" lang="en">
10812 <div class="titlepage"><div><div><h4 class="title">
10813 <a name="id2602597"></a>Name Server Statistics Counters</h4></div></div></div>
10814 <div class="informaltable"><table border="1">
10815 <colgroup>
10816 <col>
10817 <col>
10818 <col>
10819 </colgroup>
10820 <tbody>
10821 <tr>
10822 <td>
10823                       <p>
10824                         <span class="emphasis"><em>Symbol</em></span>
10825                       </p>
10826                     </td>
10827 <td>
10828                       <p>
10829                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10830                       </p>
10831                     </td>
10832 <td>
10833                       <p>
10834                         <span class="emphasis"><em>Description</em></span>
10835                       </p>
10836                     </td>
10837 </tr>
10838 <tr>
10839 <td>
10840                       <p><span><strong class="command">Requestv4</strong></span></p>
10841                     </td>
10842 <td>
10843                       <p><span><strong class="command">RQ</strong></span></p>
10844                     </td>
10845 <td>
10846                       <p>
10847                         IPv4 requests received.
10848                         Note: this also counts non query requests.
10849                       </p>
10850                     </td>
10851 </tr>
10852 <tr>
10853 <td>
10854                       <p><span><strong class="command">Requestv6</strong></span></p>
10855                     </td>
10856 <td>
10857                       <p><span><strong class="command">RQ</strong></span></p>
10858                     </td>
10859 <td>
10860                       <p>
10861                         IPv6 requests received.
10862                         Note: this also counts non query requests.
10863                       </p>
10864                     </td>
10865 </tr>
10866 <tr>
10867 <td>
10868                       <p><span><strong class="command">ReqEdns0</strong></span></p>
10869                     </td>
10870 <td>
10871                       <p><span><strong class="command"></strong></span></p>
10872                     </td>
10873 <td>
10874                       <p>
10875                         Requests with EDNS(0) received.
10876                       </p>
10877                     </td>
10878 </tr>
10879 <tr>
10880 <td>
10881                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
10882                     </td>
10883 <td>
10884                       <p><span><strong class="command"></strong></span></p>
10885                     </td>
10886 <td>
10887                       <p>
10888                         Requests with unsupported EDNS version received.
10889                       </p>
10890                     </td>
10891 </tr>
10892 <tr>
10893 <td>
10894                       <p><span><strong class="command">ReqTSIG</strong></span></p>
10895                     </td>
10896 <td>
10897                       <p><span><strong class="command"></strong></span></p>
10898                     </td>
10899 <td>
10900                       <p>
10901                         Requests with TSIG received.
10902                       </p>
10903                     </td>
10904 </tr>
10905 <tr>
10906 <td>
10907                       <p><span><strong class="command">ReqSIG0</strong></span></p>
10908                     </td>
10909 <td>
10910                       <p><span><strong class="command"></strong></span></p>
10911                     </td>
10912 <td>
10913                       <p>
10914                         Requests with SIG(0) received.
10915                       </p>
10916                     </td>
10917 </tr>
10918 <tr>
10919 <td>
10920                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
10921                     </td>
10922 <td>
10923                       <p><span><strong class="command"></strong></span></p>
10924                     </td>
10925 <td>
10926                       <p>
10927                         Requests with invalid (TSIG or SIG(0)) signature.
10928                       </p>
10929                     </td>
10930 </tr>
10931 <tr>
10932 <td>
10933                       <p><span><strong class="command">ReqTCP</strong></span></p>
10934                     </td>
10935 <td>
10936                       <p><span><strong class="command">RTCP</strong></span></p>
10937                     </td>
10938 <td>
10939                       <p>
10940                         TCP requests received.
10941                       </p>
10942                     </td>
10943 </tr>
10944 <tr>
10945 <td>
10946                       <p><span><strong class="command">AuthQryRej</strong></span></p>
10947                     </td>
10948 <td>
10949                       <p><span><strong class="command">RUQ</strong></span></p>
10950                     </td>
10951 <td>
10952                       <p>
10953                         Authoritative (non recursive) queries rejected.
10954                       </p>
10955                     </td>
10956 </tr>
10957 <tr>
10958 <td>
10959                       <p><span><strong class="command">RecQryRej</strong></span></p>
10960                     </td>
10961 <td>
10962                       <p><span><strong class="command">RURQ</strong></span></p>
10963                     </td>
10964 <td>
10965                       <p>
10966                         Recursive queries rejected.
10967                       </p>
10968                     </td>
10969 </tr>
10970 <tr>
10971 <td>
10972                       <p><span><strong class="command">XfrRej</strong></span></p>
10973                     </td>
10974 <td>
10975                       <p><span><strong class="command">RUXFR</strong></span></p>
10976                     </td>
10977 <td>
10978                       <p>
10979                         Zone transfer requests rejected.
10980                       </p>
10981                     </td>
10982 </tr>
10983 <tr>
10984 <td>
10985                       <p><span><strong class="command">UpdateRej</strong></span></p>
10986                     </td>
10987 <td>
10988                       <p><span><strong class="command">RUUpd</strong></span></p>
10989                     </td>
10990 <td>
10991                       <p>
10992                         Dynamic update requests rejected.
10993                       </p>
10994                     </td>
10995 </tr>
10996 <tr>
10997 <td>
10998                       <p><span><strong class="command">Response</strong></span></p>
10999                     </td>
11000 <td>
11001                       <p><span><strong class="command">SAns</strong></span></p>
11002                     </td>
11003 <td>
11004                       <p>
11005                         Responses sent.
11006                       </p>
11007                     </td>
11008 </tr>
11009 <tr>
11010 <td>
11011                       <p><span><strong class="command">RespTruncated</strong></span></p>
11012                     </td>
11013 <td>
11014                       <p><span><strong class="command"></strong></span></p>
11015                     </td>
11016 <td>
11017                       <p>
11018                         Truncated responses sent.
11019                       </p>
11020                     </td>
11021 </tr>
11022 <tr>
11023 <td>
11024                       <p><span><strong class="command">RespEDNS0</strong></span></p>
11025                     </td>
11026 <td>
11027                       <p><span><strong class="command"></strong></span></p>
11028                     </td>
11029 <td>
11030                       <p>
11031                         Responses with EDNS(0) sent.
11032                       </p>
11033                     </td>
11034 </tr>
11035 <tr>
11036 <td>
11037                       <p><span><strong class="command">RespTSIG</strong></span></p>
11038                     </td>
11039 <td>
11040                       <p><span><strong class="command"></strong></span></p>
11041                     </td>
11042 <td>
11043                       <p>
11044                         Responses with TSIG sent.
11045                       </p>
11046                     </td>
11047 </tr>
11048 <tr>
11049 <td>
11050                       <p><span><strong class="command">RespSIG0</strong></span></p>
11051                     </td>
11052 <td>
11053                       <p><span><strong class="command"></strong></span></p>
11054                     </td>
11055 <td>
11056                       <p>
11057                         Responses with SIG(0) sent.
11058                       </p>
11059                     </td>
11060 </tr>
11061 <tr>
11062 <td>
11063                       <p><span><strong class="command">QrySuccess</strong></span></p>
11064                     </td>
11065 <td>
11066                       <p><span><strong class="command"></strong></span></p>
11067                     </td>
11068 <td>
11069                       <p>
11070                         Queries resulted in a successful answer.
11071                         This means the query which returns a NOERROR response
11072                         with at least one answer RR.
11073                         This corresponds to the
11074                         <span><strong class="command">success</strong></span> counter
11075                         of previous versions of
11076                         <acronym class="acronym">BIND</acronym> 9.
11077                       </p>
11078                     </td>
11079 </tr>
11080 <tr>
11081 <td>
11082                       <p><span><strong class="command">QryAuthAns</strong></span></p>
11083                     </td>
11084 <td>
11085                       <p><span><strong class="command"></strong></span></p>
11086                     </td>
11087 <td>
11088                       <p>
11089                         Queries resulted in authoritative answer.
11090                       </p>
11091                     </td>
11092 </tr>
11093 <tr>
11094 <td>
11095                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
11096                     </td>
11097 <td>
11098                       <p><span><strong class="command">SNaAns</strong></span></p>
11099                     </td>
11100 <td>
11101                       <p>
11102                         Queries resulted in non authoritative answer.
11103                       </p>
11104                     </td>
11105 </tr>
11106 <tr>
11107 <td>
11108                       <p><span><strong class="command">QryReferral</strong></span></p>
11109                     </td>
11110 <td>
11111                       <p><span><strong class="command"></strong></span></p>
11112                     </td>
11113 <td>
11114                       <p>
11115                         Queries resulted in referral answer.
11116                         This corresponds to the
11117                         <span><strong class="command">referral</strong></span> counter
11118                         of previous versions of
11119                         <acronym class="acronym">BIND</acronym> 9.
11120                       </p>
11121                     </td>
11122 </tr>
11123 <tr>
11124 <td>
11125                       <p><span><strong class="command">QryNxrrset</strong></span></p>
11126                     </td>
11127 <td>
11128                       <p><span><strong class="command"></strong></span></p>
11129                     </td>
11130 <td>
11131                       <p>
11132                         Queries resulted in NOERROR responses with no data.
11133                         This corresponds to the
11134                         <span><strong class="command">nxrrset</strong></span> counter
11135                         of previous versions of
11136                         <acronym class="acronym">BIND</acronym> 9.
11137                       </p>
11138                     </td>
11139 </tr>
11140 <tr>
11141 <td>
11142                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
11143                     </td>
11144 <td>
11145                       <p><span><strong class="command">SFail</strong></span></p>
11146                     </td>
11147 <td>
11148                       <p>
11149                         Queries resulted in SERVFAIL.
11150                       </p>
11151                     </td>
11152 </tr>
11153 <tr>
11154 <td>
11155                       <p><span><strong class="command">QryFORMERR</strong></span></p>
11156                     </td>
11157 <td>
11158                       <p><span><strong class="command">SFErr</strong></span></p>
11159                     </td>
11160 <td>
11161                       <p>
11162                         Queries resulted in FORMERR.
11163                       </p>
11164                     </td>
11165 </tr>
11166 <tr>
11167 <td>
11168                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
11169                     </td>
11170 <td>
11171                       <p><span><strong class="command">SNXD</strong></span></p>
11172                     </td>
11173 <td>
11174                       <p>
11175                         Queries resulted in NXDOMAIN.
11176                         This corresponds to the
11177                         <span><strong class="command">nxdomain</strong></span> counter
11178                         of previous versions of
11179                         <acronym class="acronym">BIND</acronym> 9.
11180                       </p>
11181                     </td>
11182 </tr>
11183 <tr>
11184 <td>
11185                       <p><span><strong class="command">QryRecursion</strong></span></p>
11186                     </td>
11187 <td>
11188                       <p><span><strong class="command">RFwdQ</strong></span></p>
11189                     </td>
11190 <td>
11191                       <p>
11192                         Queries which caused the server
11193                         to perform recursion in order to find the final answer.
11194                         This corresponds to the
11195                         <span><strong class="command">recursion</strong></span> counter
11196                         of previous versions of
11197                         <acronym class="acronym">BIND</acronym> 9.
11198                       </p>
11199                     </td>
11200 </tr>
11201 <tr>
11202 <td>
11203                       <p><span><strong class="command">QryDuplicate</strong></span></p>
11204                     </td>
11205 <td>
11206                       <p><span><strong class="command">RDupQ</strong></span></p>
11207                     </td>
11208 <td>
11209                       <p>
11210                         Queries which the server attempted to
11211                         recurse but discovered an existing query with the same
11212                         IP address, port, query ID, name, type and class
11213                         already being processed.
11214                         This corresponds to the
11215                         <span><strong class="command">duplicate</strong></span> counter
11216                         of previous versions of
11217                         <acronym class="acronym">BIND</acronym> 9.
11218                       </p>
11219                     </td>
11220 </tr>
11221 <tr>
11222 <td>
11223                       <p><span><strong class="command">QryDropped</strong></span></p>
11224                     </td>
11225 <td>
11226                       <p><span><strong class="command"></strong></span></p>
11227                     </td>
11228 <td>
11229                       <p>
11230                         Recursive queries for which the server
11231                         discovered an excessive number of existing
11232                         recursive queries for the same name, type and
11233                         class and were subsequently dropped.
11234                         This is the number of dropped queries due to
11235                         the reason explained with the
11236                         <span><strong class="command">clients-per-query</strong></span>
11237                         and
11238                         <span><strong class="command">max-clients-per-query</strong></span>
11239                         options
11240                         (see the description about
11241                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
11242                         This corresponds to the
11243                         <span><strong class="command">dropped</strong></span> counter
11244                         of previous versions of
11245                         <acronym class="acronym">BIND</acronym> 9.
11246                       </p>
11247                     </td>
11248 </tr>
11249 <tr>
11250 <td>
11251                       <p><span><strong class="command">QryFailure</strong></span></p>
11252                     </td>
11253 <td>
11254                       <p><span><strong class="command"></strong></span></p>
11255                     </td>
11256 <td>
11257                       <p>
11258                         Other query failures.
11259                         This corresponds to the
11260                         <span><strong class="command">failure</strong></span> counter
11261                         of previous versions of
11262                         <acronym class="acronym">BIND</acronym> 9.
11263                         Note: this counter is provided mainly for
11264                         backward compatibility with the previous versions.
11265                         Normally a more fine-grained counters such as
11266                         <span><strong class="command">AuthQryRej</strong></span> and
11267                         <span><strong class="command">RecQryRej</strong></span>
11268                         that would also fall into this counter are provided,
11269                         and so this counter would not be of much
11270                         interest in practice.
11271                       </p>
11272                     </td>
11273 </tr>
11274 <tr>
11275 <td>
11276                       <p><span><strong class="command">XfrReqDone</strong></span></p>
11277                     </td>
11278 <td>
11279                       <p><span><strong class="command"></strong></span></p>
11280                     </td>
11281 <td>
11282                       <p>
11283                         Requested zone transfers completed.
11284                       </p>
11285                     </td>
11286 </tr>
11287 <tr>
11288 <td>
11289                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
11290                     </td>
11291 <td>
11292                       <p><span><strong class="command"></strong></span></p>
11293                     </td>
11294 <td>
11295                       <p>
11296                         Update requests forwarded.
11297                       </p>
11298                     </td>
11299 </tr>
11300 <tr>
11301 <td>
11302                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
11303                     </td>
11304 <td>
11305                       <p><span><strong class="command"></strong></span></p>
11306                     </td>
11307 <td>
11308                       <p>
11309                         Update responses forwarded.
11310                       </p>
11311                     </td>
11312 </tr>
11313 <tr>
11314 <td>
11315                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
11316                     </td>
11317 <td>
11318                       <p><span><strong class="command"></strong></span></p>
11319                     </td>
11320 <td>
11321                       <p>
11322                         Dynamic update forward failed.
11323                       </p>
11324                     </td>
11325 </tr>
11326 <tr>
11327 <td>
11328                       <p><span><strong class="command">UpdateDone</strong></span></p>
11329                     </td>
11330 <td>
11331                       <p><span><strong class="command"></strong></span></p>
11332                     </td>
11333 <td>
11334                       <p>
11335                         Dynamic updates completed.
11336                       </p>
11337                     </td>
11338 </tr>
11339 <tr>
11340 <td>
11341                       <p><span><strong class="command">UpdateFail</strong></span></p>
11342                     </td>
11343 <td>
11344                       <p><span><strong class="command"></strong></span></p>
11345                     </td>
11346 <td>
11347                       <p>
11348                         Dynamic updates failed.
11349                       </p>
11350                     </td>
11351 </tr>
11352 <tr>
11353 <td>
11354                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
11355                     </td>
11356 <td>
11357                       <p><span><strong class="command"></strong></span></p>
11358                     </td>
11359 <td>
11360                       <p>
11361                         Dynamic updates rejected due to prerequisite failure.
11362                       </p>
11363                     </td>
11364 </tr>
11365 <tr>
11366 <td>
11367                       <p><span><strong class="command">RateDropped</strong></span></p>
11368                     </td>
11369 <td>
11370                       <p><span><strong class="command"></strong></span></p>
11371                     </td>
11372 <td>
11373                       <p>
11374                         Responses dropped by rate limits.
11375                       </p>
11376                     </td>
11377 </tr>
11378 <tr>
11379 <td>
11380                       <p><span><strong class="command">RateSlipped</strong></span></p>
11381                     </td>
11382 <td>
11383                       <p><span><strong class="command"></strong></span></p>
11384                     </td>
11385 <td>
11386                       <p>
11387                         Responses truncated by rate limits.
11388                       </p>
11389                     </td>
11390 </tr>
11391 <tr>
11392 <td>
11393                       <p><span><strong class="command">RPZRewrites</strong></span></p>
11394                     </td>
11395 <td>
11396                       <p><span><strong class="command"></strong></span></p>
11397                     </td>
11398 <td>
11399                       <p>
11400                         Response policy zone rewrites.
11401                       </p>
11402                     </td>
11403 </tr>
11404 </tbody>
11405 </table></div>
11406 </div>
11407 <div class="sect3" lang="en">
11408 <div class="titlepage"><div><div><h4 class="title">
11409 <a name="id2604302"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
11410 <div class="informaltable"><table border="1">
11411 <colgroup>
11412 <col>
11413 <col>
11414 </colgroup>
11415 <tbody>
11416 <tr>
11417 <td>
11418                       <p>
11419                         <span class="emphasis"><em>Symbol</em></span>
11420                       </p>
11421                     </td>
11422 <td>
11423                       <p>
11424                         <span class="emphasis"><em>Description</em></span>
11425                       </p>
11426                     </td>
11427 </tr>
11428 <tr>
11429 <td>
11430                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
11431                     </td>
11432 <td>
11433                       <p>
11434                         IPv4 notifies sent.
11435                       </p>
11436                     </td>
11437 </tr>
11438 <tr>
11439 <td>
11440                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
11441                     </td>
11442 <td>
11443                       <p>
11444                         IPv6 notifies sent.
11445                       </p>
11446                     </td>
11447 </tr>
11448 <tr>
11449 <td>
11450                       <p><span><strong class="command">NotifyInv4</strong></span></p>
11451                     </td>
11452 <td>
11453                       <p>
11454                         IPv4 notifies received.
11455                       </p>
11456                     </td>
11457 </tr>
11458 <tr>
11459 <td>
11460                       <p><span><strong class="command">NotifyInv6</strong></span></p>
11461                     </td>
11462 <td>
11463                       <p>
11464                         IPv6 notifies received.
11465                       </p>
11466                     </td>
11467 </tr>
11468 <tr>
11469 <td>
11470                       <p><span><strong class="command">NotifyRej</strong></span></p>
11471                     </td>
11472 <td>
11473                       <p>
11474                         Incoming notifies rejected.
11475                       </p>
11476                     </td>
11477 </tr>
11478 <tr>
11479 <td>
11480                       <p><span><strong class="command">SOAOutv4</strong></span></p>
11481                     </td>
11482 <td>
11483                       <p>
11484                         IPv4 SOA queries sent.
11485                       </p>
11486                     </td>
11487 </tr>
11488 <tr>
11489 <td>
11490                       <p><span><strong class="command">SOAOutv6</strong></span></p>
11491                     </td>
11492 <td>
11493                       <p>
11494                         IPv6 SOA queries sent.
11495                       </p>
11496                     </td>
11497 </tr>
11498 <tr>
11499 <td>
11500                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
11501                     </td>
11502 <td>
11503                       <p>
11504                         IPv4 AXFR requested.
11505                       </p>
11506                     </td>
11507 </tr>
11508 <tr>
11509 <td>
11510                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
11511                     </td>
11512 <td>
11513                       <p>
11514                         IPv6 AXFR requested.
11515                       </p>
11516                     </td>
11517 </tr>
11518 <tr>
11519 <td>
11520                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
11521                     </td>
11522 <td>
11523                       <p>
11524                         IPv4 IXFR requested.
11525                       </p>
11526                     </td>
11527 </tr>
11528 <tr>
11529 <td>
11530                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
11531                     </td>
11532 <td>
11533                       <p>
11534                         IPv6 IXFR requested.
11535                       </p>
11536                     </td>
11537 </tr>
11538 <tr>
11539 <td>
11540                       <p><span><strong class="command">XfrSuccess</strong></span></p>
11541                     </td>
11542 <td>
11543                       <p>
11544                         Zone transfer requests succeeded.
11545                       </p>
11546                     </td>
11547 </tr>
11548 <tr>
11549 <td>
11550                       <p><span><strong class="command">XfrFail</strong></span></p>
11551                     </td>
11552 <td>
11553                       <p>
11554                         Zone transfer requests failed.
11555                       </p>
11556                     </td>
11557 </tr>
11558 </tbody>
11559 </table></div>
11560 </div>
11561 <div class="sect3" lang="en">
11562 <div class="titlepage"><div><div><h4 class="title">
11563 <a name="id2604685"></a>Resolver Statistics Counters</h4></div></div></div>
11564 <div class="informaltable"><table border="1">
11565 <colgroup>
11566 <col>
11567 <col>
11568 <col>
11569 </colgroup>
11570 <tbody>
11571 <tr>
11572 <td>
11573                       <p>
11574                         <span class="emphasis"><em>Symbol</em></span>
11575                       </p>
11576                     </td>
11577 <td>
11578                       <p>
11579                         <span class="emphasis"><em>BIND8 Symbol</em></span>
11580                       </p>
11581                     </td>
11582 <td>
11583                       <p>
11584                         <span class="emphasis"><em>Description</em></span>
11585                       </p>
11586                     </td>
11587 </tr>
11588 <tr>
11589 <td>
11590                       <p><span><strong class="command">Queryv4</strong></span></p>
11591                     </td>
11592 <td>
11593                       <p><span><strong class="command">SFwdQ</strong></span></p>
11594                     </td>
11595 <td>
11596                       <p>
11597                         IPv4 queries sent.
11598                       </p>
11599                     </td>
11600 </tr>
11601 <tr>
11602 <td>
11603                       <p><span><strong class="command">Queryv6</strong></span></p>
11604                     </td>
11605 <td>
11606                       <p><span><strong class="command">SFwdQ</strong></span></p>
11607                     </td>
11608 <td>
11609                       <p>
11610                         IPv6 queries sent.
11611                       </p>
11612                     </td>
11613 </tr>
11614 <tr>
11615 <td>
11616                       <p><span><strong class="command">Responsev4</strong></span></p>
11617                     </td>
11618 <td>
11619                       <p><span><strong class="command">RR</strong></span></p>
11620                     </td>
11621 <td>
11622                       <p>
11623                         IPv4 responses received.
11624                       </p>
11625                     </td>
11626 </tr>
11627 <tr>
11628 <td>
11629                       <p><span><strong class="command">Responsev6</strong></span></p>
11630                     </td>
11631 <td>
11632                       <p><span><strong class="command">RR</strong></span></p>
11633                     </td>
11634 <td>
11635                       <p>
11636                         IPv6 responses received.
11637                       </p>
11638                     </td>
11639 </tr>
11640 <tr>
11641 <td>
11642                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
11643                     </td>
11644 <td>
11645                       <p><span><strong class="command">RNXD</strong></span></p>
11646                     </td>
11647 <td>
11648                       <p>
11649                         NXDOMAIN received.
11650                       </p>
11651                     </td>
11652 </tr>
11653 <tr>
11654 <td>
11655                       <p><span><strong class="command">SERVFAIL</strong></span></p>
11656                     </td>
11657 <td>
11658                       <p><span><strong class="command">RFail</strong></span></p>
11659                     </td>
11660 <td>
11661                       <p>
11662                         SERVFAIL received.
11663                       </p>
11664                     </td>
11665 </tr>
11666 <tr>
11667 <td>
11668                       <p><span><strong class="command">FORMERR</strong></span></p>
11669                     </td>
11670 <td>
11671                       <p><span><strong class="command">RFErr</strong></span></p>
11672                     </td>
11673 <td>
11674                       <p>
11675                         FORMERR received.
11676                       </p>
11677                     </td>
11678 </tr>
11679 <tr>
11680 <td>
11681                       <p><span><strong class="command">OtherError</strong></span></p>
11682                     </td>
11683 <td>
11684                       <p><span><strong class="command">RErr</strong></span></p>
11685                     </td>
11686 <td>
11687                       <p>
11688                         Other errors received.
11689                       </p>
11690                     </td>
11691 </tr>
11692 <tr>
11693 <td>
11694                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
11695                                                  </td>
11696 <td>
11697                       <p><span><strong class="command"></strong></span></p>
11698                     </td>
11699 <td>
11700                       <p>
11701                         EDNS(0) query failures.
11702                       </p>
11703                     </td>
11704 </tr>
11705 <tr>
11706 <td>
11707                       <p><span><strong class="command">Mismatch</strong></span></p>
11708                     </td>
11709 <td>
11710                       <p><span><strong class="command">RDupR</strong></span></p>
11711                     </td>
11712 <td>
11713                       <p>
11714                         Mismatch responses received.
11715                         The DNS ID, response's source address,
11716                         and/or the response's source port does not
11717                         match what was expected.
11718                         (The port must be 53 or as defined by
11719                         the <span><strong class="command">port</strong></span> option.)
11720                         This may be an indication of a cache
11721                         poisoning attempt.
11722                       </p>
11723                     </td>
11724 </tr>
11725 <tr>
11726 <td>
11727                       <p><span><strong class="command">Truncated</strong></span></p>
11728                     </td>
11729 <td>
11730                       <p><span><strong class="command"></strong></span></p>
11731                     </td>
11732 <td>
11733                       <p>
11734                         Truncated responses received.
11735                       </p>
11736                     </td>
11737 </tr>
11738 <tr>
11739 <td>
11740                       <p><span><strong class="command">Lame</strong></span></p>
11741                     </td>
11742 <td>
11743                       <p><span><strong class="command">RLame</strong></span></p>
11744                     </td>
11745 <td>
11746                       <p>
11747                         Lame delegations received.
11748                       </p>
11749                     </td>
11750 </tr>
11751 <tr>
11752 <td>
11753                       <p><span><strong class="command">Retry</strong></span></p>
11754                     </td>
11755 <td>
11756                       <p><span><strong class="command">SDupQ</strong></span></p>
11757                     </td>
11758 <td>
11759                       <p>
11760                         Query retries performed.
11761                       </p>
11762                     </td>
11763 </tr>
11764 <tr>
11765 <td>
11766                       <p><span><strong class="command">QueryAbort</strong></span></p>
11767                     </td>
11768 <td>
11769                       <p><span><strong class="command"></strong></span></p>
11770                     </td>
11771 <td>
11772                       <p>
11773                         Queries aborted due to quota control.
11774                       </p>
11775                     </td>
11776 </tr>
11777 <tr>
11778 <td>
11779                       <p><span><strong class="command">QuerySockFail</strong></span></p>
11780                     </td>
11781 <td>
11782                       <p><span><strong class="command"></strong></span></p>
11783                     </td>
11784 <td>
11785                       <p>
11786                         Failures in opening query sockets.
11787                         One common reason for such failures is a
11788                         failure of opening a new socket due to a
11789                         limitation on file descriptors.
11790                       </p>
11791                     </td>
11792 </tr>
11793 <tr>
11794 <td>
11795                       <p><span><strong class="command">QueryTimeout</strong></span></p>
11796                     </td>
11797 <td>
11798                       <p><span><strong class="command"></strong></span></p>
11799                     </td>
11800 <td>
11801                       <p>
11802                         Query timeouts.
11803                       </p>
11804                     </td>
11805 </tr>
11806 <tr>
11807 <td>
11808                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
11809                     </td>
11810 <td>
11811                       <p><span><strong class="command">SSysQ</strong></span></p>
11812                     </td>
11813 <td>
11814                       <p>
11815                         IPv4 NS address fetches invoked.
11816                       </p>
11817                     </td>
11818 </tr>
11819 <tr>
11820 <td>
11821                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
11822                     </td>
11823 <td>
11824                       <p><span><strong class="command">SSysQ</strong></span></p>
11825                     </td>
11826 <td>
11827                       <p>
11828                         IPv6 NS address fetches invoked.
11829                       </p>
11830                     </td>
11831 </tr>
11832 <tr>
11833 <td>
11834                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
11835                     </td>
11836 <td>
11837                       <p><span><strong class="command"></strong></span></p>
11838                     </td>
11839 <td>
11840                       <p>
11841                         IPv4 NS address fetch failed.
11842                       </p>
11843                     </td>
11844 </tr>
11845 <tr>
11846 <td>
11847                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
11848                     </td>
11849 <td>
11850                       <p><span><strong class="command"></strong></span></p>
11851                     </td>
11852 <td>
11853                       <p>
11854                         IPv6 NS address fetch failed.
11855                       </p>
11856                     </td>
11857 </tr>
11858 <tr>
11859 <td>
11860                       <p><span><strong class="command">ValAttempt</strong></span></p>
11861                     </td>
11862 <td>
11863                       <p><span><strong class="command"></strong></span></p>
11864                     </td>
11865 <td>
11866                       <p>
11867                         DNSSEC validation attempted.
11868                       </p>
11869                     </td>
11870 </tr>
11871 <tr>
11872 <td>
11873                       <p><span><strong class="command">ValOk</strong></span></p>
11874                     </td>
11875 <td>
11876                       <p><span><strong class="command"></strong></span></p>
11877                     </td>
11878 <td>
11879                       <p>
11880                         DNSSEC validation succeeded.
11881                       </p>
11882                     </td>
11883 </tr>
11884 <tr>
11885 <td>
11886                       <p><span><strong class="command">ValNegOk</strong></span></p>
11887                     </td>
11888 <td>
11889                       <p><span><strong class="command"></strong></span></p>
11890                     </td>
11891 <td>
11892                       <p>
11893                         DNSSEC validation on negative information succeeded.
11894                       </p>
11895                     </td>
11896 </tr>
11897 <tr>
11898 <td>
11899                       <p><span><strong class="command">ValFail</strong></span></p>
11900                     </td>
11901 <td>
11902                       <p><span><strong class="command"></strong></span></p>
11903                     </td>
11904 <td>
11905                       <p>
11906                         DNSSEC validation failed.
11907                       </p>
11908                     </td>
11909 </tr>
11910 <tr>
11911 <td>
11912                       <p><span><strong class="command">QryRTTnn</strong></span></p>
11913                     </td>
11914 <td>
11915                       <p><span><strong class="command"></strong></span></p>
11916                     </td>
11917 <td>
11918                       <p>
11919                         Frequency table on round trip times (RTTs) of
11920                         queries.
11921                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
11922                         frequency.
11923                         In the sequence of
11924                         <span><strong class="command">nn_1</strong></span>,
11925                         <span><strong class="command">nn_2</strong></span>,
11926                         ...,
11927                         <span><strong class="command">nn_m</strong></span>,
11928                         the value of <span><strong class="command">nn_i</strong></span> is the
11929                         number of queries whose RTTs are between
11930                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
11931                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
11932                         For the sake of convenience we define
11933                         <span><strong class="command">nn_0</strong></span> to be 0.
11934                         The last entry should be represented as
11935                         <span><strong class="command">nn_m+</strong></span>, which means the
11936                         number of queries whose RTTs are equal to or over
11937                         <span><strong class="command">nn_m</strong></span> milliseconds.
11938                       </p>
11939                     </td>
11940 </tr>
11941 </tbody>
11942 </table></div>
11943 </div>
11944 <div class="sect3" lang="en">
11945 <div class="titlepage"><div><div><h4 class="title">
11946 <a name="id2605707"></a>Socket I/O Statistics Counters</h4></div></div></div>
11947 <p>
11948               Socket I/O statistics counters are defined per socket
11949               types, which are
11950               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
11951               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
11952               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
11953               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
11954               <span><strong class="command">Unix</strong></span> (Unix Domain), and
11955               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
11956               socket module).
11957               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
11958               represents a socket type.
11959               Not all counters are available for all socket types;
11960               exceptions are noted in the description field.
11961             </p>
11962 <div class="informaltable"><table border="1">
11963 <colgroup>
11964 <col>
11965 <col>
11966 </colgroup>
11967 <tbody>
11968 <tr>
11969 <td>
11970                       <p>
11971                         <span class="emphasis"><em>Symbol</em></span>
11972                       </p>
11973                     </td>
11974 <td>
11975                       <p>
11976                         <span class="emphasis"><em>Description</em></span>
11977                       </p>
11978                     </td>
11979 </tr>
11980 <tr>
11981 <td>
11982                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
11983                     </td>
11984 <td>
11985                       <p>
11986                         Sockets opened successfully.
11987                         This counter is not applicable to the
11988                         <span><strong class="command">FDwatch</strong></span> type.
11989                       </p>
11990                     </td>
11991 </tr>
11992 <tr>
11993 <td>
11994                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
11995                     </td>
11996 <td>
11997                       <p>
11998                         Failures of opening sockets.
11999                         This counter is not applicable to the
12000                         <span><strong class="command">FDwatch</strong></span> type.
12001                       </p>
12002                     </td>
12003 </tr>
12004 <tr>
12005 <td>
12006                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
12007                     </td>
12008 <td>
12009                       <p>
12010                         Sockets closed.
12011                       </p>
12012                     </td>
12013 </tr>
12014 <tr>
12015 <td>
12016                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
12017                     </td>
12018 <td>
12019                       <p>
12020                         Failures of binding sockets.
12021                       </p>
12022                     </td>
12023 </tr>
12024 <tr>
12025 <td>
12026                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
12027                     </td>
12028 <td>
12029                       <p>
12030                         Failures of connecting sockets.
12031                       </p>
12032                     </td>
12033 </tr>
12034 <tr>
12035 <td>
12036                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
12037                     </td>
12038 <td>
12039                       <p>
12040                         Connections established successfully.
12041                       </p>
12042                     </td>
12043 </tr>
12044 <tr>
12045 <td>
12046                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
12047                     </td>
12048 <td>
12049                       <p>
12050                         Failures of accepting incoming connection requests.
12051                         This counter is not applicable to the
12052                         <span><strong class="command">UDP</strong></span> and
12053                         <span><strong class="command">FDwatch</strong></span> types.
12054                       </p>
12055                     </td>
12056 </tr>
12057 <tr>
12058 <td>
12059                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
12060                     </td>
12061 <td>
12062                       <p>
12063                         Incoming connections successfully accepted.
12064                         This counter is not applicable to the
12065                         <span><strong class="command">UDP</strong></span> and
12066                         <span><strong class="command">FDwatch</strong></span> types.
12067                       </p>
12068                     </td>
12069 </tr>
12070 <tr>
12071 <td>
12072                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
12073                     </td>
12074 <td>
12075                       <p>
12076                         Errors in socket send operations.
12077                         This counter corresponds
12078                         to <span><strong class="command">SErr</strong></span> counter of
12079                         <span><strong class="command">BIND</strong></span> 8.
12080                       </p>
12081                     </td>
12082 </tr>
12083 <tr>
12084 <td>
12085                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
12086                     </td>
12087 <td>
12088                       <p>
12089                         Errors in socket receive operations.
12090                         This includes errors of send operations on a
12091                         connected UDP socket notified by an ICMP error
12092                         message.
12093                       </p>
12094                     </td>
12095 </tr>
12096 </tbody>
12097 </table></div>
12098 </div>
12099 <div class="sect3" lang="en">
12100 <div class="titlepage"><div><div><h4 class="title">
12101 <a name="id2606149"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
12102 <p>
12103               Most statistics counters that were available
12104               in <span><strong class="command">BIND</strong></span> 8 are also supported in
12105               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
12106               Here are notes about other counters that do not appear
12107               in these tables.
12108             </p>
12109 <div class="variablelist"><dl>
12110 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
12111 <dd><p>
12112                     These counters are not supported
12113                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
12114                     the notion of <span class="emphasis"><em>forwarding</em></span>
12115                     as <span><strong class="command">BIND</strong></span> 8 did.
12116                   </p></dd>
12117 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
12118 <dd><p>
12119                     This counter is accessible in the Incoming Queries section.
12120                   </p></dd>
12121 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
12122 <dd><p>
12123                     This counter is accessible in the Incoming Requests section.
12124                   </p></dd>
12125 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
12126 <dd><p>
12127                     This counter is not supported
12128                     because <span><strong class="command">BIND</strong></span> 9 does not care
12129                     about IP options in the first place.
12130                   </p></dd>
12131 </dl></div>
12132 </div>
12133 </div>
12134 </div>
12135 </div>
12136 <div class="navfooter">
12137 <hr>
12138 <table width="100%" summary="Navigation footer">
12139 <tr>
12140 <td width="40%" align="left">
12141 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
12142 <td width="20%" align="center"> </td>
12143 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
12144 </td>
12145 </tr>
12146 <tr>
12147 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
12148 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
12149 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
12150 </tr>
12151 </table>
12152 </div>
12153 <p style="text-align: center;">BIND 9.10.2-P4</p>
12154 </body>
12155 </html>