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Linux: Multiple IP on Single Interface




Let’s assume that we want to create three additional virtual interfaces to bind three IP addresses (172.16.16.126, 172.16.16.127, and 172.16.16.128) to the NIC. So, we need to create three additional alias files, while “ifcfg-eth0” keeps the same primary IP address. This is how we moving forward to setup three aliases to bind the following IP addresses.
Adapter            IP Address                Type
-------------------------------------------------
eth0              172.16.16.125            Primary
eth0:0            172.16.16.126            Alias 1
eth0:1            172.16.16.127            Alias 2
eth0:2            172.16.16.128            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 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 a file “ifcfg-eth0” and view the contents.
[root@tecmint network-scripts]# vi ifcfg-eth0
DEVICE="eth0"
BOOTPROTO=static
ONBOOT=yes
TYPE="Ethernet"
IPADDR=172.16.16.125
NETMASK=255.255.255.224
GATEWAY=172.16.16.100
HWADDR=00:0C:29:28:FD:4C
Here we only need two parameters (DEVICE and IPADDR). So, open each file with VI editor and rename the DEVICE name to its corresponding alias and change the IPADDR address. For example, open files “ifcfg-eth0:0“, “ifcfg-eth0:1” and “ifcfg-eth0:2” using VI editor and change both the parameters. Finally it will look similar to below.
ifcfg-eth0:0 will look similar to below. RED marked are the changes.
ifcfg-eth0:0
DEVICE="eth0:0"
BOOTPROTO=static
ONBOOT=yes
TYPE="Ethernet"
IPADDR=172.16.16.126
NETMASK=255.255.255.224
GATEWAY=172.16.16.100
HWADDR=00:0C:29:28:FD:4C
Once, you’ve made all changes, save all your changes and restart/start the network service for the changes to reflect.
[root@tecmint network-scripts]# /etc/init.d/network restart
To verify all the aliases (virtual interface) are up and running, you can use “ifconfig” or “ip” command.


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