Normally when you add a new IP to a network interface in a RedHat based system you create a file ifcfg-eth0:x in /etc/sysconfig/network-scripts/.
For example:
/etc/sysconfig/network-scripts/ifcfg-eth0:0
DEVICE=eth0:0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.100
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
TYPE=Ethernet
Create a file /etc/sysconfig/network-scripts/ifcfg-eth0-range0 if this doesn’t exist, or just add to it if you already have it, the following lines:
/etc/sysconfig/network-scripts/ifcfg-eth0-range0
IPADDR_START=192.168.0.100
IPADDR_END=192.168.0.200
CLONENUM_START=0
where: IPADDR_START is the first IP and IPADDR_END is the last IP in the range. CLONENUM_START is the number that will be assigned to the first IP alias interface (eth0:0 in this example).
If you need to add more ranges of IPs then just use a different file for ex. ifcfg-eth0-range1, for each one of the ranges. You need to be careful and use the proper CLONENUM_START to not overwrite other aliases. Once you have configured the range/s of IPs you just need to restart the network service in order to activate it:
service network restart
Note: don’t use this method on a CPanel based system. Even though this will work fine, it is better to use CPanel/WHM in this case so CPanel can manage all the IPs properly.