How to setup More Than One IP address on single NIC in Linux

Setting up two IP address on single NIC

There are some times we require two IP address to set up so that we can make a Linux box as a router. It can be possible without even having two NIC cards. We can configure more than two different IP address on single Network Card as shown below:

This example is on Ethernet.

STEP 1: Setting up first IP address. Edit /etc/sysconfig/network-scripts/ifcfg-eth0 on Red-hat 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

Note: 

• We can assign virtual IP to the same interface with ifconfig but that one is not permanent so not giving info on that.
• We can assign up to 16 virtual IP address to a single NIC card.