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: /etc/sysconfig/network-scripts/ifcfg-eth0-range0
IPADDR_START=192.168.1.50
IPADD........