The steps to add additional IP’s are:
Login into the server as the root user:
Change to /etc/sysconfig/network-scripts directory
cd /etc/sysconfig/network-scripts
Assuming that the network interface name is eth0
cp ifcfg-eth0 as ifcfg-eth0:1
Edit the ifcfg-eth0:1 file and change the DEVICE parameter to DEVICE=eth0:1
Change the other parameters in the file such as IPADDR to the new IP address.
After this restart the network service:
service network restart