5 # allow packets coming from foo to bar through.
7 pass in from 10.1.1.2 to 10.2.1.1
9 # allow any TCP packets from the same subnet as foo is on through to host
10 # 10.1.1.2 if they are destined for port 6667.
12 pass in proto tcp from 10.2.2.2/24 to 10.1.1.2/32 port = 6667
14 # allow in UDP packets which are NOT from port 53 and are destined for
17 pass in proto udp from 10.2.2.2 port != 53 to localhost
19 # block all ICMP unreachables.
21 block in proto icmp from any to any icmp-type unreach
23 # allow packets through which have a non-standard IP header length (ie there
24 # are IP options such as source-routing present).
26 pass in from any to any with ipopts