Concept of iptables It is a realy rule table in which the IP communication rules are. There are groups of these rules, and it’s called “chain'. iptables configuration Configuration file You can see the configurations in the file /etc/iptables/rule.v4. Here is a sample line in the file. -A chain-outgoing-services -s 192.168.100.50/32 -d 188.8.131.52/32 -p tcp -m tcp --dport 22 -m comment --comment "This is a comment." -j ACCEPT http://web.mit.edu/rhel-doc/4/RH-DOCS/rhel-rg-en-4/s1-iptables-options.html -A chain-outgoing-services: Append the rule to chain chain-outgoing-services.