The Linux iptables Firewall

An unexpected source of server connectivity issues for brand new servers is frequently the iptables firewall. This is installed by default under Fedora and Red Hat and usually allows only a limited range of traffic.

Determining Whether iptables Is Running

You can easily test whether iptables is running by using the /etc/init.d/iptables script with the status qualifier. If it isn't running you'll get a very short listing of the firewall rules. Here is some sample output:

     [root@zero root]# service iptables status
     Firewall is stopped.
     [root@zero root]#

How to Stop iptables

If your Linux box is already protected by a firewall, you may want to temporarily disable iptables using the same /etc/init.d/iptables script with the stop qualifier:

     [root@bigboy tmp]# service iptables stop
     Flushing firewall rules: [  OK  ]
     Setting chains to policy ACCEPT: filter [  OK  ]
     Unloading iptables modules: [  OK  ]
     [root@bigboy tmp]#

How to Configure iptables Rules

Stopping iptables may not be a good permanent solution, especially if your network isn't protected by a firewall. You can read more about configuring iptables in Chapter 14, "Linux Firewalls Using iptables."