Iptables

iptables is a sub-project of netfilter

iptables is the userspace command line program used to configure the Linux 2.4.x and 2.6.x IPv4 packet filtering ruleset. It is targeted towards system administrators.

Since Network Address Translation is also configured from the packet filter ruleset, iptables is used for this, too.

The iptables package also includes ip6tables. ip6tables is used for configuring the IPv6 packet filter.

iptables requires a kernel that features the ip_tables packet filter. This includes all 2.4.x and 2.6.x kernel releases.

Main Features

• listing the contents of the packet filter ruleset
• adding/removing/modifying rules in the packet filter ruleset
• listing/zeroing per-rule counters of the packet filter ruleset

http://netfilter.org/projects/iptables