Setting up two IP address on one NIC

This is a small how-to to set up two are more IP address on single LAN card. There are some times which require two IP address to set up so that we can make a Linux box as a router. This can be possible without even having two NIC cards. We can configure two different IP address on single Network Card as shown below.

Setting up 2 IP address on “One” NIC. This example is on ethernet.

STEP 1:Setting up first IP address. Edit /etc/sysconfig/network-scripts/ifcfg-eth0 on Redhat Linux box and give the following entries as shown.

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

DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.1.10
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes

STEP 2: Setting up second IP address. Create one file as /etc/sysconfig/network-scripts/ifcfg-eth0:1 and give the entries as below in to this file.

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

DEVICE=eth0:1
BOOTPROTO=static
IPADDR=192.168.1.11
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes

STEP 3: Once you configure above files and save them. Now reload the network service on your machine.

service network reload

STEP 4: Check if you get the IP address assigned to the eth0 and eth0:1 interfaces respectively.

ifconfig

Note1: We can assign virtual IP to the same interface with ifconfig but that one is not permanent so not giving info on that.

Note2: We can assign up to 16 virtual IP address to a single NIC card.