Adding additional IP's

[Happy Clicker]

How to set multiple IP addresses using Linux command line

Go to /etc/sysconfig/network-scripts
Make multiple copies of ifcfg-eth0 and name them as ifcfg-eth0:0, ifcfg-eth0:1 etc.
Open each of them and at least change the IPADDR to your chosen IP address and the NETMASK to the subnet mask for that IP address.
A sample entry would look like this:

DEVICE=eth0:0
BOOTPROTO=static
IPADDR=111.100.111.21
NETMASK=255.255.255.0
ONBOOT=yes

Restart the network:
/sbin/service network restart

You are done!
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Red Hat / CentOS / Fedora Multiple IP address range

You can assign multiple ip address range as follows to eth0:

vi /etc/sysconfig/network-scripts/ifcfg-eth0-range0

Append following code from 111.00.111.100 to 111.00.111.300:

IPADDR_START=111.00.111.100
IPADDR_END=111.00.111.300
CLONENUM_START=0
NETMASK=255.255.255.0

Save and close the file.