Sometimes we need to block some unnecessary port to block or disable as of security. It’s a good practice to keep only required port open and block all other port which are not in used. First of all I will show you how to open/add port in firewall.
Step 1: Add Port in firewall
As you can see there is only one port is added in my machine which is for postgresql
Let’s suppose, we have to add port 80 in firewall using firewalld command in redhat 7 version and you can use iptables in redhat version 6.
firewall-cmd –permanent –zone=public –add-port=80/tcp
We have added port 80 of httpd in firewall it will work until you do not reload the firewall
Step 2 : Check port has been added in firewall
Step 3 : Now restart the service of firewall.
Systemctl restart firewalld