iptables configuration on a linux server

• List current tables with line numbers and stats

iptables -L INPUT --line-numbers -v

• Append another rule

iptables -A INPUT -s 58.245.23.126/24 -j DROP

• Delete rule #3

iptables -D INPUT 3

• The moment you apply IPTABLE rule it immediately becomes active.But it will not survive a reboot.
• To be able to survive IPTABLES a reboot in your network configuration file /etc/network/interfaces file (referring to a Debian/Ubuntu system) you need to add:

pre-up  iptables-restore < firewall.txt

Making changes persistent in CentOS 5

iptables rules are stored in memory. If the system is restarted, all rules are lost.

To save rules:

/sbin/service iptables save

This executes the iptables init script, which runs the /sbin/iptables-save program and writes the current iptables configuration to /etc/sysconfig/iptables. The existing /etc/sysconfig/iptables file is saved as /etc/sysconfig/iptables.save.

The next time the system boots, the iptables init script reapplies the rules saved in /etc/sysconfig/iptables by using the /sbin/iptables-restore command.