Add a Virtual IP Address in Linux

nano /etc/sysconfig/network-scripts/ifcfg-eth0

Should look something like this

DEVICE=eth0 BOOTPROTO=static BROADCAST=172.16.0.255 HWADDR=00:00:00:00:00:00 IPADDR=172.16.0.2 NETMASK=255.255.255.0 NETWORK=172.16.0.0 ONBOOT=yes

Duplicate that and open the new file

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0 nano /etc/sysconfig/network-scripts/ifcfg-eth0:0

Change device name, set new IP, remove reference to hardware

DEVICE=eth0:0 BOOTPROTO=static BROADCAST=172.16.0.255 IPADDR=172.16.0.3 NETMASK=255.255.255.0 NETWORK=172.16.0.0 ONBOOT=yes