IP aliasing

[Vinil]

The concept of creating or configuring multiple IP addresses on a single network interface is called IP aliasing. The main advantage of using this IP aliasing is, you don’t need to have a physical adapter attached to each IP, but instead you can create multiple or many virtual interfaces (aliases) to a single physical card.

To assign multiple ip addresses on a snigle interface, first of all we need to identify the default interface for the Ethernet device. Suppose the interface name is "ifcfg-eth0" and we want to create three additional virtual interfaces to bind three IP addresses 10.20.30.20, 10.20.30.30, and 10.20.30.40.

So, we need to create three additional alias files, while "ifcfg-eth0" keeps the same primary IP address.

Code: [Select]

Adapter            IP Address                Type
-------------------------------------------------
eth0                 10.20.30.10           Primary
eth0:0               10.20.30.20           Alias 1
eth0:1               10.20.30.30           Alias 2
eth0:2               10.20.30.40           Alias 3

Where ":X" is the device (interface) number to create the aliases for interface eth0. For each alias you must assign a number sequentially. For example, we are copying existing parameters of interface "ifcfg-eth0" in virtual interfaces called ifcfg-eth0:0, ifcfg-eth0:1 and ifcfg-eth0:2. Go into the network directory and create the files as shown below.

# cd /etc/sysconfig/network-scripts/
# cp ifcfg-eth0 ifcfg-eth0:0
# cp ifcfg-eth0 ifcfg-eth0:1
# cp ifcfg-eth0 ifcfg-eth0:2

Open the file "ifcfg-eth0" and view the contents.

#cat ifcfg-eth0

DEVICE="eth0"
BOOTPROTO=static
ONBOOT=yes
IPADDR=10.20.30.10

Then we need to make changes for two parameters (DEVICE and IPADDR) in aliases files "ifcfg-eth0:0", "ifcfg-eth0:1" and "ifcfg-eth0:2"


Here is the ifcfg-eth0:0 file after making the necessary changes.

#cat ifcfg-eth0:0

DEVICE="eth0:0"
BOOTPROTO=static
ONBOOT=yes
IPADDR=10.20.30.20

Similarly make the changes in remaining files (ifcfg-eth0:1 and ifcfg-eth0:2).

Once, you’ve made all changes, save all your changes and restart the network service for the changes to reflect.

Code: [Select]

# /etc/init.d/network restart


That's all ...