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1 /proc/sys/net/ipv4/* Variables:
3 ip_forward - BOOLEAN
4 0 - disabled (default)
5 not 0 - enabled
7 Forward Packets between interfaces.
9 This variable is special, its change resets all configuration
10 parameters to their default state (RFC1122 for hosts, RFC1812
11 for routers)
13 ip_default_ttl - INTEGER
14 default 64
16 ip_no_pmtu_disc - BOOLEAN
17 Disable Path MTU Discovery.
18 default FALSE
20 min_pmtu - INTEGER
21 default 562 - minimum discovered Path MTU
23 mtu_expires - INTEGER
24 Time, in seconds, that cached PMTU information is kept.
26 min_adv_mss - INTEGER
27 The advertised MSS depends on the first hop route MTU, but will
28 never be lower than this setting.
30 IP Fragmentation:
32 ipfrag_high_thresh - INTEGER
33 Maximum memory used to reassemble IP fragments. When
34 ipfrag_high_thresh bytes of memory is allocated for this purpose,
35 the fragment handler will toss packets until ipfrag_low_thresh
36 is reached.
38 ipfrag_low_thresh - INTEGER
39 See ipfrag_high_thresh
41 ipfrag_time - INTEGER
42 Time in seconds to keep an IP fragment in memory.
44 ipfrag_secret_interval - INTEGER
45 Regeneration interval (in seconds) of the hash secret (or lifetime
46 for the hash secret) for IP fragments.
47 Default: 600
49 INET peer storage:
51 inet_peer_threshold - INTEGER
52 The approximate size of the storage. Starting from this threshold
53 entries will be thrown aggressively. This threshold also determines
54 entries' time-to-live and time intervals between garbage collection
55 passes. More entries, less time-to-live, less GC interval.
57 inet_peer_minttl - INTEGER
58 Minimum time-to-live of entries. Should be enough to cover fragment
59 time-to-live on the reassembling side. This minimum time-to-live is
60 guaranteed if the pool size is less than inet_peer_threshold.
61 Measured in jiffies(1).
63 inet_peer_maxttl - INTEGER
64 Maximum time-to-live of entries. Unused entries will expire after
65 this period of time if there is no memory pressure on the pool (i.e.
66 when the number of entries in the pool is very small).
67 Measured in jiffies(1).
69 inet_peer_gc_mintime - INTEGER
70 Minimum interval between garbage collection passes. This interval is
71 in effect under high memory pressure on the pool.
72 Measured in jiffies(1).
74 inet_peer_gc_maxtime - INTEGER
75 Minimum interval between garbage collection passes. This interval is
76 in effect under low (or absent) memory pressure on the pool.
77 Measured in jiffies(1).
79 TCP variables:
81 tcp_syn_retries - INTEGER
82 Number of times initial SYNs for an active TCP connection attempt
83 will be retransmitted. Should not be higher than 255. Default value
84 is 5, which corresponds to ~180seconds.
86 tcp_synack_retries - INTEGER
87 Number of times SYNACKs for a passive TCP connection attempt will
88 be retransmitted. Should not be higher than 255. Default value
89 is 5, which corresponds to ~180seconds.
91 tcp_keepalive_time - INTEGER
92 How often TCP sends out keepalive messages when keepalive is enabled.
93 Default: 2hours.
95 tcp_keepalive_probes - INTEGER
96 How many keepalive probes TCP sends out, until it decides that the
97 connection is broken. Default value: 9.
99 tcp_keepalive_intvl - INTEGER
100 How frequently the probes are send out. Multiplied by
101 tcp_keepalive_probes it is time to kill not responding connection,
102 after probes started. Default value: 75sec i.e. connection
103 will be aborted after ~11 minutes of retries.
105 tcp_retries1 - INTEGER
106 How many times to retry before deciding that something is wrong
107 and it is necessary to report this suspicion to network layer.
108 Minimal RFC value is 3, it is default, which corresponds
109 to ~3sec-8min depending on RTO.
111 tcp_retries2 - INTEGER
112 How may times to retry before killing alive TCP connection.
113 RFC1122 says that the limit should be longer than 100 sec.
114 It is too small number. Default value 15 corresponds to ~13-30min
115 depending on RTO.
117 tcp_orphan_retries - INTEGER
118 How may times to retry before killing TCP connection, closed
119 by our side. Default value 7 corresponds to ~50sec-16min
120 depending on RTO. If you machine is loaded WEB server,
121 you should think about lowering this value, such sockets
122 may consume significant resources. Cf. tcp_max_orphans.
124 tcp_fin_timeout - INTEGER
125 Time to hold socket in state FIN-WAIT-2, if it was closed
126 by our side. Peer can be broken and never close its side,
127 or even died unexpectedly. Default value is 60sec.
128 Usual value used in 2.2 was 180 seconds, you may restore
129 it, but remember that if your machine is even underloaded WEB server,
130 you risk to overflow memory with kilotons of dead sockets,
131 FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
132 because they eat maximum 1.5K of memory, but they tend
133 to live longer. Cf. tcp_max_orphans.
135 tcp_max_tw_buckets - INTEGER
136 Maximal number of timewait sockets held by system simultaneously.
137 If this number is exceeded time-wait socket is immediately destroyed
138 and warning is printed. This limit exists only to prevent
139 simple DoS attacks, you _must_ not lower the limit artificially,
140 but rather increase it (probably, after increasing installed memory),
141 if network conditions require more than default value.
143 tcp_tw_recycle - BOOLEAN
144 Enable fast recycling TIME-WAIT sockets. Default value is 0.
145 It should not be changed without advice/request of technical
146 experts.
148 tcp_tw_reuse - BOOLEAN
149 Allow to reuse TIME-WAIT sockets for new connections when it is
150 safe from protocol viewpoint. Default value is 0.
151 It should not be changed without advice/request of technical
152 experts.
154 tcp_max_orphans - INTEGER
155 Maximal number of TCP sockets not attached to any user file handle,
156 held by system. If this number is exceeded orphaned connections are
157 reset immediately and warning is printed. This limit exists
158 only to prevent simple DoS attacks, you _must_ not rely on this
159 or lower the limit artificially, but rather increase it
160 (probably, after increasing installed memory),
161 if network conditions require more than default value,
162 and tune network services to linger and kill such states
163 more aggressively. Let me to remind again: each orphan eats
164 up to ~64K of unswappable memory.
166 tcp_abort_on_overflow - BOOLEAN
167 If listening service is too slow to accept new connections,
168 reset them. Default state is FALSE. It means that if overflow
169 occurred due to a burst, connection will recover. Enable this
170 option _only_ if you are really sure that listening daemon
171 cannot be tuned to accept connections faster. Enabling this
172 option can harm clients of your server.
174 tcp_syncookies - BOOLEAN
175 Only valid when the kernel was compiled with CONFIG_SYNCOOKIES
176 Send out syncookies when the syn backlog queue of a socket
177 overflows. This is to prevent against the common 'syn flood attack'
178 Default: FALSE
180 Note, that syncookies is fallback facility.
181 It MUST NOT be used to help highly loaded servers to stand
182 against legal connection rate. If you see synflood warnings
183 in your logs, but investigation shows that they occur
184 because of overload with legal connections, you should tune
185 another parameters until this warning disappear.
186 See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
188 syncookies seriously violate TCP protocol, do not allow
189 to use TCP extensions, can result in serious degradation
190 of some services (f.e. SMTP relaying), visible not by you,
191 but your clients and relays, contacting you. While you see
192 synflood warnings in logs not being really flooded, your server
193 is seriously misconfigured.
195 tcp_stdurg - BOOLEAN
196 Use the Host requirements interpretation of the TCP urg pointer field.
197 Most hosts use the older BSD interpretation, so if you turn this on
198 Linux might not communicate correctly with them.
199 Default: FALSE
201 tcp_max_syn_backlog - INTEGER
202 Maximal number of remembered connection requests, which are
203 still did not receive an acknowledgment from connecting client.
204 Default value is 1024 for systems with more than 128Mb of memory,
205 and 128 for low memory machines. If server suffers of overload,
206 try to increase this number.
208 tcp_window_scaling - BOOLEAN
209 Enable window scaling as defined in RFC1323.
211 tcp_timestamps - BOOLEAN
212 Enable timestamps as defined in RFC1323.
214 tcp_sack - BOOLEAN
215 Enable select acknowledgments (SACKS).
217 tcp_fack - BOOLEAN
218 Enable FACK congestion avoidance and fast retransmission.
219 The value is not used, if tcp_sack is not enabled.
221 tcp_dsack - BOOLEAN
222 Allows TCP to send "duplicate" SACKs.
224 tcp_ecn - BOOLEAN
225 Enable Explicit Congestion Notification in TCP.
227 tcp_reordering - INTEGER
228 Maximal reordering of packets in a TCP stream.
229 Default: 3
231 tcp_retrans_collapse - BOOLEAN
232 Bug-to-bug compatibility with some broken printers.
233 On retransmit try to send bigger packets to work around bugs in
234 certain TCP stacks.
236 tcp_wmem - vector of 3 INTEGERs: min, default, max
237 min: Amount of memory reserved for send buffers for TCP socket.
238 Each TCP socket has rights to use it due to fact of its birth.
239 Default: 4K
241 default: Amount of memory allowed for send buffers for TCP socket
242 by default. This value overrides net.core.wmem_default used
243 by other protocols, it is usually lower than net.core.wmem_default.
244 Default: 16K
246 max: Maximal amount of memory allowed for automatically selected
247 send buffers for TCP socket. This value does not override
248 net.core.wmem_max, "static" selection via SO_SNDBUF does not use this.
249 Default: 128K
251 tcp_rmem - vector of 3 INTEGERs: min, default, max
252 min: Minimal size of receive buffer used by TCP sockets.
253 It is guaranteed to each TCP socket, even under moderate memory
254 pressure.
255 Default: 8K
257 default: default size of receive buffer used by TCP sockets.
258 This value overrides net.core.rmem_default used by other protocols.
259 Default: 87380 bytes. This value results in window of 65535 with
260 default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
261 less for default tcp_app_win. See below about these variables.
263 max: maximal size of receive buffer allowed for automatically
264 selected receiver buffers for TCP socket. This value does not override
265 net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
266 Default: 87380*2 bytes.
268 tcp_mem - vector of 3 INTEGERs: min, pressure, max
269 low: below this number of pages TCP is not bothered about its
270 memory appetite.
272 pressure: when amount of memory allocated by TCP exceeds this number
273 of pages, TCP moderates its memory consumption and enters memory
274 pressure mode, which is exited when memory consumption falls
275 under "low".
277 high: number of pages allowed for queueing by all TCP sockets.
279 Defaults are calculated at boot time from amount of available
280 memory.
282 tcp_app_win - INTEGER
283 Reserve max(window/2^tcp_app_win, mss) of window for application
284 buffer. Value 0 is special, it means that nothing is reserved.
285 Default: 31
287 tcp_adv_win_scale - INTEGER
288 Count buffering overhead as bytes/2^tcp_adv_win_scale
289 (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
290 if it is <= 0.
291 Default: 2
293 tcp_rfc1337 - BOOLEAN
294 If set, the TCP stack behaves conforming to RFC1337. If unset,
295 we are not conforming to RFC, but prevent TCP TIME_WAIT
296 assassination.
297 Default: 0
299 tcp_low_latency - BOOLEAN
300 If set, the TCP stack makes decisions that prefer lower
301 latency as opposed to higher throughput. By default, this
302 option is not set meaning that higher throughput is preferred.
303 An example of an application where this default should be
304 changed would be a Beowulf compute cluster.
305 Default: 0
307 tcp_westwood - BOOLEAN
308 Enable TCP Westwood+ congestion control algorithm.
309 TCP Westwood+ is a sender-side only modification of the TCP Reno
310 protocol stack that optimizes the performance of TCP congestion
311 control. It is based on end-to-end bandwidth estimation to set
312 congestion window and slow start threshold after a congestion
313 episode. Using this estimation, TCP Westwood+ adaptively sets a
314 slow start threshold and a congestion window which takes into
315 account the bandwidth used at the time congestion is experienced.
316 TCP Westwood+ significantly increases fairness wrt TCP Reno in
317 wired networks and throughput over wireless links.
318 Default: 0
320 tcp_vegas_cong_avoid - BOOLEAN
321 Enable TCP Vegas congestion avoidance algorithm.
322 TCP Vegas is a sender-side only change to TCP that anticipates
323 the onset of congestion by estimating the bandwidth. TCP Vegas
324 adjusts the sending rate by modifying the congestion
325 window. TCP Vegas should provide less packet loss, but it is
326 not as aggressive as TCP Reno.
327 Default:0
329 tcp_bic - BOOLEAN
330 Enable BIC TCP congestion control algorithm.
331 BIC-TCP is a sender-side only change that ensures a linear RTT
332 fairness under large windows while offering both scalability and
333 bounded TCP-friendliness. The protocol combines two schemes
334 called additive increase and binary search increase. When the
335 congestion window is large, additive increase with a large
336 increment ensures linear RTT fairness as well as good
337 scalability. Under small congestion windows, binary search
338 increase provides TCP friendliness.
339 Default: 0
341 tcp_bic_low_window - INTEGER
342 Sets the threshold window (in packets) where BIC TCP starts to
343 adjust the congestion window. Below this threshold BIC TCP behaves
344 the same as the default TCP Reno.
345 Default: 14
347 tcp_bic_fast_convergence - BOOLEAN
348 Forces BIC TCP to more quickly respond to changes in congestion
349 window. Allows two flows sharing the same connection to converge
350 more rapidly.
351 Default: 1
353 tcp_default_win_scale - INTEGER
354 Sets the minimum window scale TCP will negotiate for on all
355 conections.
356 Default: 7
358 tcp_tso_win_divisor - INTEGER
359 This allows control over what percentage of the congestion window
360 can be consumed by a single TSO frame.
361 The setting of this parameter is a choice between burstiness and
362 building larger TSO frames.
363 Default: 8
365 tcp_frto - BOOLEAN
366 Enables F-RTO, an enhanced recovery algorithm for TCP retransmission
367 timeouts. It is particularly beneficial in wireless environments
368 where packet loss is typically due to random radio interference
369 rather than intermediate router congestion.
371 somaxconn - INTEGER
372 Limit of socket listen() backlog, known in userspace as SOMAXCONN.
373 Defaults to 128. See also tcp_max_syn_backlog for additional tuning
374 for TCP sockets.
376 IP Variables:
378 ip_local_port_range - 2 INTEGERS
379 Defines the local port range that is used by TCP and UDP to
380 choose the local port. The first number is the first, the
381 second the last local port number. Default value depends on
382 amount of memory available on the system:
383 > 128Mb 32768-61000
384 < 128Mb 1024-4999 or even less.
385 This number defines number of active connections, which this
386 system can issue simultaneously to systems not supporting
387 TCP extensions (timestamps). With tcp_tw_recycle enabled
388 (i.e. by default) range 1024-4999 is enough to issue up to
389 2000 connections per second to systems supporting timestamps.
391 ip_nonlocal_bind - BOOLEAN
392 If set, allows processes to bind() to non-local IP addresses,
393 which can be quite useful - but may break some applications.
394 Default: 0
396 ip_dynaddr - BOOLEAN
397 If set non-zero, enables support for dynamic addresses.
398 If set to a non-zero value larger than 1, a kernel log
399 message will be printed when dynamic address rewriting
400 occurs.
401 Default: 0
403 icmp_echo_ignore_all - BOOLEAN
404 icmp_echo_ignore_broadcasts - BOOLEAN
405 If either is set to true, then the kernel will ignore either all
406 ICMP ECHO requests sent to it or just those to broadcast/multicast
407 addresses, respectively.
409 icmp_ratelimit - INTEGER
410 Limit the maximal rates for sending ICMP packets whose type matches
411 icmp_ratemask (see below) to specific targets.
412 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
413 Default: 100
415 icmp_ratemask - INTEGER
416 Mask made of ICMP types for which rates are being limited.
417 Significant bits: IHGFEDCBA9876543210
418 Default mask: 0000001100000011000 (6168)
420 Bit definitions (see include/linux/icmp.h):
421 0 Echo Reply
422 3 Destination Unreachable *
423 4 Source Quench *
424 5 Redirect
425 8 Echo Request
426 B Time Exceeded *
427 C Parameter Problem *
428 D Timestamp Request
429 E Timestamp Reply
430 F Info Request
431 G Info Reply
432 H Address Mask Request
433 I Address Mask Reply
435 * These are rate limited by default (see default mask above)
437 icmp_ignore_bogus_error_responses - BOOLEAN
438 Some routers violate RFC1122 by sending bogus responses to broadcast
439 frames. Such violations are normally logged via a kernel warning.
440 If this is set to TRUE, the kernel will not give such warnings, which
441 will avoid log file clutter.
442 Default: FALSE
444 igmp_max_memberships - INTEGER
445 Change the maximum number of multicast groups we can subscribe to.
446 Default: 20
448 conf/interface/* changes special settings per interface (where "interface" is
449 the name of your network interface)
450 conf/all/* is special, changes the settings for all interfaces
453 log_martians - BOOLEAN
454 Log packets with impossible addresses to kernel log.
455 log_martians for the interface will be enabled if at least one of
456 conf/{all,interface}/log_martians is set to TRUE,
457 it will be disabled otherwise
459 accept_redirects - BOOLEAN
460 Accept ICMP redirect messages.
461 accept_redirects for the interface will be enabled if:
462 - both conf/{all,interface}/accept_redirects are TRUE in the case forwarding
463 for the interface is enabled
464 or
465 - at least one of conf/{all,interface}/accept_redirects is TRUE in the case
466 forwarding for the interface is disabled
467 accept_redirects for the interface will be disabled otherwise
468 default TRUE (host)
469 FALSE (router)
471 forwarding - BOOLEAN
472 Enable IP forwarding on this interface.
474 mc_forwarding - BOOLEAN
475 Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
476 and a multicast routing daemon is required.
477 conf/all/mc_forwarding must also be set to TRUE to enable multicast routing
478 for the interface
480 medium_id - INTEGER
481 Integer value used to differentiate the devices by the medium they
482 are attached to. Two devices can have different id values when
483 the broadcast packets are received only on one of them.
484 The default value 0 means that the device is the only interface
485 to its medium, value of -1 means that medium is not known.
487 Currently, it is used to change the proxy_arp behavior:
488 the proxy_arp feature is enabled for packets forwarded between
489 two devices attached to different media.
491 proxy_arp - BOOLEAN
492 Do proxy arp.
493 proxy_arp for the interface will be enabled if at least one of
494 conf/{all,interface}/proxy_arp is set to TRUE,
495 it will be disabled otherwise
497 shared_media - BOOLEAN
498 Send(router) or accept(host) RFC1620 shared media redirects.
499 Overrides ip_secure_redirects.
500 shared_media for the interface will be enabled if at least one of
501 conf/{all,interface}/shared_media is set to TRUE,
502 it will be disabled otherwise
503 default TRUE
505 secure_redirects - BOOLEAN
506 Accept ICMP redirect messages only for gateways,
507 listed in default gateway list.
508 secure_redirects for the interface will be enabled if at least one of
509 conf/{all,interface}/secure_redirects is set to TRUE,
510 it will be disabled otherwise
511 default TRUE
513 send_redirects - BOOLEAN
514 Send redirects, if router.
515 send_redirects for the interface will be enabled if at least one of
516 conf/{all,interface}/send_redirects is set to TRUE,
517 it will be disabled otherwise
518 Default: TRUE
520 bootp_relay - BOOLEAN
521 Accept packets with source address 0.b.c.d destined
522 not to this host as local ones. It is supposed, that
523 BOOTP relay daemon will catch and forward such packets.
524 conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
525 for the interface
526 default FALSE
527 Not Implemented Yet.
529 accept_source_route - BOOLEAN
530 Accept packets with SRR option.
531 conf/all/accept_source_route must also be set to TRUE to accept packets
532 with SRR option on the interface
533 default TRUE (router)
534 FALSE (host)
536 rp_filter - BOOLEAN
537 1 - do source validation by reversed path, as specified in RFC1812
538 Recommended option for single homed hosts and stub network
539 routers. Could cause troubles for complicated (not loop free)
540 networks running a slow unreliable protocol (sort of RIP),
541 or using static routes.
543 0 - No source validation.
545 conf/all/rp_filter must also be set to TRUE to do source validation
546 on the interface
548 Default value is 0. Note that some distributions enable it
549 in startup scripts.
551 arp_filter - BOOLEAN
552 1 - Allows you to have multiple network interfaces on the same
553 subnet, and have the ARPs for each interface be answered
554 based on whether or not the kernel would route a packet from
555 the ARP'd IP out that interface (therefore you must use source
556 based routing for this to work). In other words it allows control
557 of which cards (usually 1) will respond to an arp request.
559 0 - (default) The kernel can respond to arp requests with addresses
560 from other interfaces. This may seem wrong but it usually makes
561 sense, because it increases the chance of successful communication.
562 IP addresses are owned by the complete host on Linux, not by
563 particular interfaces. Only for more complex setups like load-
564 balancing, does this behaviour cause problems.
566 arp_filter for the interface will be enabled if at least one of
567 conf/{all,interface}/arp_filter is set to TRUE,
568 it will be disabled otherwise
570 arp_announce - INTEGER
571 Define different restriction levels for announcing the local
572 source IP address from IP packets in ARP requests sent on
573 interface:
574 0 - (default) Use any local address, configured on any interface
575 1 - Try to avoid local addresses that are not in the target's
576 subnet for this interface. This mode is useful when target
577 hosts reachable via this interface require the source IP
578 address in ARP requests to be part of their logical network
579 configured on the receiving interface. When we generate the
580 request we will check all our subnets that include the
581 target IP and will preserve the source address if it is from
582 such subnet. If there is no such subnet we select source
583 address according to the rules for level 2.
584 2 - Always use the best local address for this target.
585 In this mode we ignore the source address in the IP packet
586 and try to select local address that we prefer for talks with
587 the target host. Such local address is selected by looking
588 for primary IP addresses on all our subnets on the outgoing
589 interface that include the target IP address. If no suitable
590 local address is found we select the first local address
591 we have on the outgoing interface or on all other interfaces,
592 with the hope we will receive reply for our request and
593 even sometimes no matter the source IP address we announce.
595 The max value from conf/{all,interface}/arp_announce is used.
597 Increasing the restriction level gives more chance for
598 receiving answer from the resolved target while decreasing
599 the level announces more valid sender's information.
601 arp_ignore - INTEGER
602 Define different modes for sending replies in response to
603 received ARP requests that resolve local target IP addresses:
604 0 - (default): reply for any local target IP address, configured
605 on any interface
606 1 - reply only if the target IP address is local address
607 configured on the incoming interface
608 2 - reply only if the target IP address is local address
609 configured on the incoming interface and both with the
610 sender's IP address are part from same subnet on this interface
611 3 - do not reply for local addresses configured with scope host,
612 only resolutions for global and link addresses are replied
613 4-7 - reserved
614 8 - do not reply for all local addresses
616 The max value from conf/{all,interface}/arp_ignore is used
617 when ARP request is received on the {interface}
619 app_solicit - INTEGER
620 The maximum number of probes to send to the user space ARP daemon
621 via netlink before dropping back to multicast probes (see
622 mcast_solicit). Defaults to 0.
624 disable_policy - BOOLEAN
625 Disable IPSEC policy (SPD) for this interface
627 disable_xfrm - BOOLEAN
628 Disable IPSEC encryption on this interface, whatever the policy
632 tag - INTEGER
633 Allows you to write a number, which can be used as required.
634 Default value is 0.
636 (1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the
637 Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact
638 value on your system.
640 Alexey Kuznetsov.
641 kuznet@ms2.inr.ac.ru
643 Updated by:
644 Andi Kleen
645 ak@muc.de
646 Nicolas Delon
647 delon.nicolas@wanadoo.fr
652 /proc/sys/net/ipv6/* Variables:
654 IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
655 apply to IPv6 [XXX?].
657 bindv6only - BOOLEAN
658 Default value for IPV6_V6ONLY socket option,
659 which restricts use of the IPv6 socket to IPv6 communication
660 only.
661 TRUE: disable IPv4-mapped address feature
662 FALSE: enable IPv4-mapped address feature
664 Default: FALSE (as specified in RFC2553bis)
666 IPv6 Fragmentation:
668 ip6frag_high_thresh - INTEGER
669 Maximum memory used to reassemble IPv6 fragments. When
670 ip6frag_high_thresh bytes of memory is allocated for this purpose,
671 the fragment handler will toss packets until ip6frag_low_thresh
672 is reached.
674 ip6frag_low_thresh - INTEGER
675 See ip6frag_high_thresh
677 ip6frag_time - INTEGER
678 Time in seconds to keep an IPv6 fragment in memory.
680 ip6frag_secret_interval - INTEGER
681 Regeneration interval (in seconds) of the hash secret (or lifetime
682 for the hash secret) for IPv6 fragments.
683 Default: 600
685 conf/default/*:
686 Change the interface-specific default settings.
689 conf/all/*:
690 Change all the interface-specific settings.
692 [XXX: Other special features than forwarding?]
694 conf/all/forwarding - BOOLEAN
695 Enable global IPv6 forwarding between all interfaces.
697 IPv4 and IPv6 work differently here; e.g. netfilter must be used
698 to control which interfaces may forward packets and which not.
700 This also sets all interfaces' Host/Router setting
701 'forwarding' to the specified value. See below for details.
703 This referred to as global forwarding.
705 conf/interface/*:
706 Change special settings per interface.
708 The functional behaviour for certain settings is different
709 depending on whether local forwarding is enabled or not.
711 accept_ra - BOOLEAN
712 Accept Router Advertisements; autoconfigure using them.
714 Functional default: enabled if local forwarding is disabled.
715 disabled if local forwarding is enabled.
717 accept_redirects - BOOLEAN
718 Accept Redirects.
720 Functional default: enabled if local forwarding is disabled.
721 disabled if local forwarding is enabled.
723 autoconf - BOOLEAN
724 Autoconfigure addresses using Prefix Information in Router
725 Advertisements.
727 Functional default: enabled if accept_ra is enabled.
728 disabled if accept_ra is disabled.
730 dad_transmits - INTEGER
731 The amount of Duplicate Address Detection probes to send.
732 Default: 1
734 forwarding - BOOLEAN
735 Configure interface-specific Host/Router behaviour.
737 Note: It is recommended to have the same setting on all
738 interfaces; mixed router/host scenarios are rather uncommon.
740 FALSE:
742 By default, Host behaviour is assumed. This means:
744 1. IsRouter flag is not set in Neighbour Advertisements.
745 2. Router Solicitations are being sent when necessary.
746 3. If accept_ra is TRUE (default), accept Router
747 Advertisements (and do autoconfiguration).
748 4. If accept_redirects is TRUE (default), accept Redirects.
750 TRUE:
752 If local forwarding is enabled, Router behaviour is assumed.
753 This means exactly the reverse from the above:
755 1. IsRouter flag is set in Neighbour Advertisements.
756 2. Router Solicitations are not sent.
757 3. Router Advertisements are ignored.
758 4. Redirects are ignored.
760 Default: FALSE if global forwarding is disabled (default),
761 otherwise TRUE.
763 hop_limit - INTEGER
764 Default Hop Limit to set.
765 Default: 64
767 mtu - INTEGER
768 Default Maximum Transfer Unit
769 Default: 1280 (IPv6 required minimum)
771 router_solicitation_delay - INTEGER
772 Number of seconds to wait after interface is brought up
773 before sending Router Solicitations.
774 Default: 1
776 router_solicitation_interval - INTEGER
777 Number of seconds to wait between Router Solicitations.
778 Default: 4
780 router_solicitations - INTEGER
781 Number of Router Solicitations to send until assuming no
782 routers are present.
783 Default: 3
785 use_tempaddr - INTEGER
786 Preference for Privacy Extensions (RFC3041).
787 <= 0 : disable Privacy Extensions
788 == 1 : enable Privacy Extensions, but prefer public
789 addresses over temporary addresses.
790 > 1 : enable Privacy Extensions and prefer temporary
791 addresses over public addresses.
792 Default: 0 (for most devices)
793 -1 (for point-to-point devices and loopback devices)
795 temp_valid_lft - INTEGER
796 valid lifetime (in seconds) for temporary addresses.
797 Default: 604800 (7 days)
799 temp_prefered_lft - INTEGER
800 Preferred lifetime (in seconds) for temporary addresses.
801 Default: 86400 (1 day)
803 max_desync_factor - INTEGER
804 Maximum value for DESYNC_FACTOR, which is a random value
805 that ensures that clients don't synchronize with each
806 other and generate new addresses at exactly the same time.
807 value is in seconds.
808 Default: 600
810 regen_max_retry - INTEGER
811 Number of attempts before give up attempting to generate
812 valid temporary addresses.
813 Default: 5
815 max_addresses - INTEGER
816 Number of maximum addresses per interface. 0 disables limitation.
817 It is recommended not set too large value (or 0) because it would
818 be too easy way to crash kernel to allow to create too much of
819 autoconfigured addresses.
820 Default: 16
822 icmp/*:
823 ratelimit - INTEGER
824 Limit the maximal rates for sending ICMPv6 packets.
825 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
826 Default: 100
829 IPv6 Update by:
830 Pekka Savola <pekkas@netcore.fi>
831 YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
834 /proc/sys/net/bridge/* Variables:
836 bridge-nf-call-arptables - BOOLEAN
837 1 : pass bridged ARP traffic to arptables' FORWARD chain.
838 0 : disable this.
839 Default: 1
841 bridge-nf-call-iptables - BOOLEAN
842 1 : pass bridged IPv4 traffic to iptables' chains.
843 0 : disable this.
844 Default: 1
846 bridge-nf-call-ip6tables - BOOLEAN
847 1 : pass bridged IPv6 traffic to ip6tables' chains.
848 0 : disable this.
849 Default: 1
851 bridge-nf-filter-vlan-tagged - BOOLEAN
852 1 : pass bridged vlan-tagged ARP/IP traffic to arptables/iptables.
853 0 : disable this.
854 Default: 1
857 UNDOCUMENTED:
859 dev_weight FIXME
860 discovery_slots FIXME
861 discovery_timeout FIXME
862 fast_poll_increase FIXME
863 ip6_queue_maxlen FIXME
864 lap_keepalive_time FIXME
865 lo_cong FIXME
866 max_baud_rate FIXME
867 max_dgram_qlen FIXME
868 max_noreply_time FIXME
869 max_tx_data_size FIXME
870 max_tx_window FIXME
871 min_tx_turn_time FIXME
872 mod_cong FIXME
873 no_cong FIXME
874 no_cong_thresh FIXME
875 slot_timeout FIXME
876 warn_noreply_time FIXME
878 $Id: ip-sysctl.txt,v 1.20 2001/12/13 09:00:18 davem Exp $