You can add several virtual IP addresses to a physical network interface. A good starting point is to copy the interface definition file of the device you want to add a virtual IP address to.
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0
You may have to modify ifcfg-eth0 to match your physical interface name.
Now you can edit the new file ifcfg-eth0:0 and specify the network settings of the virtual interface.
To make the changes take effect please restart the network services using:
service network restart