How to configure additional IP address in Linux - Open source guides, news, articles and scripts

How to configure additional IP address in Linux
This tutorial will show you how to configure additional IP address on NIC under Red Hat Linux or Fedora Core.

The following procedure uses eth0 as an example for assigning a second TCP/IP address.

Use the following command to add the IP address:
ifconfig eth0:1 xxx.xxx.xxx.xxx

Where xxx.xxx.xxx.xxx is the actual IP address.
Note that eth0:1 is in case you add only a second IP address. Same way you can add eth0:2, eth0:3 and so on.

To make the changes permanent you will need to add the IP also in the network scripts which are being started on system boot.

1. Verify that your /etc/sysconfig/network-scripts/ifcfg-eth0 file does not have a GATEWAY= parameter in it. If it does, remove it and add that parameter to /etc/sysconfig/network.

2. Copy your /etc/sysconfig/network-scripts/ifcfg-eth0 file to a new file called: /etc/sysconfig/network-scripts/ifcfg-eth0:1

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

3. In /etc/sysconfig/network-scripts/ifcfg-eth0:1 change DEVICE=eth0 to DEVICE=eth0:1

4. In /etc/sysconfig/network-scripts/ifcfg-eth0:1 modify IPADDR= to match the additional TCP/IP address you wish to use.

5. Start the secondary interface:
ifup eth0:1