Steps to check the opened ports in IP tables
To view the ports that are already opened in the server, execute the following command.
netstat -plan |grep LISTEN
Steps to open a new port in IP tables
Before opening a port, you should be aware of why are you opening the port and what is the port being used for.
Save the existing IP tables.
root@server [~]# /etc/init.d/iptables save
Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
To open a port, execute the commands below.
iptables -A allowed -p tcp –dport portno -s IPaddress -j ACCEPT
iptables -A allowed -p udp –dport portno -s IPaddress -j ACCEPT
To allow all IP address,
iptables -A INPUT -i eth0 -p tcp -m tcp –dport portno -j ACCEPT
Check whether the Port is allowed.
root@server [~]# iptables -nL | grep :3306
ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 tcp dpt:3306
ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 tcp dpt:3306
