IPTABLES

To add a new rule in iptables use the below method:

append the below lines to /etc/sysconfig/iptables and /etc/sysconfig/iptables.save file

# Generated by iptables-save v1.2.11 on Tue Oct 14 18:47:16 2008
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [3541478:1038277365]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -i eth1 -p udp -m udp --dport 1194 -m state --state NEW -j ACCEPT
-A INPUT -i tap0 -j DROP
-A INPUT -j RH-Firewall-1-INPUT
-A INPUT -s 172.16.20.0/255.255.255.0 -p udp -m udp --dport 53 -j ACCEPT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p ipv6-crypt -j ACCEPT
-A RH-Firewall-1-INPUT -p ipv6-auth -j ACCEPT
-A RH-Firewall-1-INPUT -d 224.0.0.251 -p udp -m udp --dport 5353 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 8980 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 23 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT

Reff. Site: http://www.cyberciti.biz/faq/howto-rhel-linux-open-port-using-iptables/