This is actually very simple and this example assumes your network device is "eth0"
In Centos your network config would be the following: /etc/sysconfig/network-scripts/ifcfg-eth0
Take the same path and just add a "-range0"
So to add a range create the following file:
Obviously change the IPADDR_START and IPADDR_END to suit your subnet and actual range you are looking for.
This is much easier than having eth0:0 to eth:50 etc... set manually or