Linux Networking Configuring Multiple IP Addresses

Configuring Multiple IP Addresses

Configuring Multiple IP Addresses on a single NIC.

In the last section, we have learned to configure IP address for your interface. It is also possible to configure more than one IP addresses on a single NIC example: eth0. For this, we need to create a new child interface with name eth0:X where X can have the values 0, 1, 2, ........

The steps are very similar to the one we explained in the previous section (eth0). You need to verify the following details.

* First ensure the parent real interface (eth0) exists

* Verify that no other IP aliases with the same name exists with the name you plan to use. In this we want to create interface eth0:0.

* Create the virtual interface with the ifconfig command

As we discussed earlier, we shall create the file /etc/sysconfig/network-scripts/ifcfg-eth0:0 with the following contents.

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DEVICE=Interface:X (eth0:0)

ONBOOT=yes

BOOTPROTO=static

IPADDR=IP_address

NETMASK=NET_MASK

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Once it is done, please use the following commands to activate the interface.

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root@Basil15099/~# ifdown Interface:X

root@Basil15099/~# ifup Interface:X
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In my example, I have created a child interface eth0:0 with the IP address 192.168.1.101. So I had to modify the file /etc/sysconfig/network-scripts/ifcfg-eth0:0 with the following details.

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DEVICE=eth0:0

ONBOOT=yes

BOOTPROTO=static

IPADDR=192.169.1.101

NETMASK=255.255.255.0

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Then I executed the following commands to activate my child interface.

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root@Basil15099/~# ifdown eth0:0

root@Basil15099/~# ifup eth0:0
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If you are not using Fedora Linux, please use the following command to configure IP address for your child interface.

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root@Basil15099/~# ifconfig interface:X IP_address netmask NET_MASK up
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As you know this configuration will last till the next reboot. So in order to make the configuration permanent, you need to put the above command in the /etc/rc.local file.

So in my example, the command will be as follows.

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root@Basil15099/~# ifconfig eth0:0 192.169.1.101 netmask 255.255.255.0 up
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Thats all :-)