Create file: /etc/sysconfig/network-scripts/ifcfg-eth0:0
DEVICE="eth0:0" BOOTPROTO=static ONBOOT=yes TYPE="Ethernet" IPADDR=18.104.22.168 #HWADDR=00:0C:29:28:4C:4C #GATEWAY=22.214.171.124 NETMASK=255.255.255.0
do this for each additional IP address, you only need to increase virtual interface number by one for each additional IP.
Like eg. eth0:1, eth0:2, eth0:3 ...
**if you don't have HWADDR then delete that line.
service network restart
Check all IP's configured on the server
if your new IP address is listed then you have successfully added a new IP address.