IP aliasing - CentOS 6

Problem

The following document will outline the steps needed to assign multiple IP addresses to a single interface on CentOS 6. This process is called IP aliasing. You can make temporary or permanent IP aliases, but we will be focusing on making permanent aliases.

tl;dr

cd /etc/sysconfig/network-scripts/
cp ifcfg-eth0 ifcfg-eth0:1
sed -i "s/DEVICE=eth0/DEVICE=eth0:1/" ifcfg-eth0:1
sed -i "s/IPADDR=[Your primary IP]/IPADDR=[Your secondary IP]/" ifcfg-eth0:1
ifup eth0:1

Solution

Creating an IP alias is very simple. First, lets create a new file in the network-scripts directory using your favourite editor.

vi /etc/sysconfig/network-scripts/ifcfg-eth0:1

DEVICE=eth0:1
BOOTPROTO=none
IPADDR=[Your secondary IP]
NETMASK=[Your netmask]
NM_CONTROLLED=no
ONBOOT=yes
TYPE=Ethernet

Now that we have created the file, turn on the interface

ifup eth0:1