The iptables utility controls the network packet filtering code in the Linux kernel. If you need to set up firewalls and/or IP masquerading, you should install this tool.
The iptables feature is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. Several different tables may be defined. Each table contains a number of built-in chains and may also contain user-defined chains.
Each chain is a list of rules which can match a set of packets. Each rule specifies what to do with a packet that matches. This is called a ‘target’, which may be a jump to a user-defined chain in the same table
# service iptables
# /sbin/service snmpd help
Usage: /etc/init.d/iptables {start|stop|restart|condrestart|status|panic|save}
/etc/sysconfig/iptables – iptables rules
/etc/sysconfig/iptables-config – iptables configuration