How to add a range of IP's

For a small range of IPs, you can manually add each IP to a file called ifcfg-eth0:x, which resides in /etc/sysconfig/network-scripts/.
For instance, if you want to add 10 IP addresses, you'll have to create 10 files in that directory, starting with ifcfg-eth0:0 and ending
with ifcfg-eth0:10. Each file will contain:

CODE

DEVICE=eth0:0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.2
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
TYPE=Ethernet

The IPADDR will increase from 192.168.0.2 to 192.168.0.12.

But what if you have to add 100 IP addresses? It could be physically possible to manually add a file for each of them. But how about
1000 IP addresses? Or 10,000? Fortunately, RedHat based systems offer a quick and easy way to bind a range of IPs, eliminating the
need to create a lot of files and saving a lot of your time.

Create a file called ifcfg-eth0-range0 in the /etc/sysconfig/network-scripts directory. This file must contain the following strings:

CODE

IPADDR_START=192.168.0.10
IPADDR_END=192.168.0.110
CLONENUM_START=0

Let's see what each of them does:

IPADDR_START: This is the first IP from the address range you want to bind to your ethernet device.
IPADDR_END: This is, of course, the last IP from that address range.
CLONENUM_START: This is the number that will be assigned to the first IP alias interface. For instance, if your Internet interface is eth0 and CLONENUM_START is 0, then this config file will create 100 interfaces starting with eth0:0 (eth0:0, eth0:1, eth0:2 etc) and ending with eth0:100.

NOTE! Be careful if you need to add more ranges of IPs. You'll have to use a proper value for CLONENUM_START. For instance, if you need to add a second range with 100 IPs besides the one above, create a new file called ifcfg-eth0-range1 and set the CLONENUM_START to 101 so an overwrite will be avoided.

After making any changes to any of the files created in the network-scripts directory, you have to run the following command so the changes are applied and the address range is activated:

# service network restart