Iptables

# apt-get install iptables

iptables uses policy chains to decide the path of a packet to, from, through your system.

Tables

• FILTER: is the default table with chains INPUT, FORWARD and OUTPUT
• NAT: used to translate the packet source/destination field with chains PREROUTING, OUTPUT and POSTROUTING
• MANGLE: packet alteration with chains INPUT, FORWARD, POSTROUTING, PREROUTING and OUTPUT
• RAW

Chains

• INPUT: for packet to local machine
• FORWARD: for packet destined to another net

Jumps

• http://www.faqs.org/docs/iptables/targets.html