1. Login to the server as root user.

2.

cd /etc/sysconfig/network-scripts 

3. Check for existing network adapters with the command:

ls ifcfg-*

4. Copy ifcfg-eth0 to ifcfg-eth0:0

cp ifcfg-eth0 ifcfg-eth0:0

5. Edit the file

vi ifcfg-eth0:0 and change the following lines

   DEVICE=eth0:0
   IPADDR=x.x.x.x (The ip you want to be added to the server)

Another important parameter in this file is the ONBOOT =yes, because if you forget to set this parameter to Yes, after a reboot the ip’s that you had added just now will be lost.

Make sure for permanent addition of the ip in the server that ONBOOT is set to yes.