Setting up multiple IP addresses on a single NIC

May 20, 2005 Posted by Ravi
In linux, you can bind multiple IP addresses on a single NIC. This is usually done in case you are using your linux machine as a web server and is hosting multiple domains and you want to bind each domain to a unique IP address. This is how it is done.

Let us assume that you already have a NIC which is bound with a static IP address. Then you will have a file called /etc/sysconfig/network-scripts/ifcfg-eth0 .My ifcfg-eth0 file has the following entries:
# File: ifcfg-eth0
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.1
NETMASK=255.255.255.0
BROADCAST=192.168.0.255
NETWORK=192.168.0.0
HWADDR=00:80:48:34:C2:84

Now to bind another IP address to the same NIC, I create a copy of the above file ifcfg-eth0 and name it as ifcfg-eth0:1
# cd /etc/sysconfig/networking-scripts
# cp ifcfg-eth0  ifcfg-eth0:1

Now just change the values of the DEVICE and IPADDR in the file as follows:
# File: ifcfg-eth0:1
DEVICE=eth0:1
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.5
NETMASK=255.255.255.0
BROADCAST=192.168.0.255
NETWORK=192.168.0.0
HWADDR=00:80:48:34:C2:84
And lastly, restart the networking service. If you are using RedHat, then it is as simple as :
# service network restart

Note: If you do not know how to configure a NIC, see my previous posts - How to install a network card in Linux and How to assign an IP address.
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3 comments:

  • 5/31/2006 09:35:00 AM

    This is more of a Debian/Ubuntu method:

    in /ect/network/interfaces

    you'll see this or something very simular
    -------------------------------------------
    auto lo eth0

    iface lo inet loopback

    iface eth0 inet static
    address xxx.xxx.xxx.xxx #original
    netmask 255.255.255.255
    broadcast 0.0.0.0
    up ip route replace 169.254.1.1 dev eth0
    up ip route add default via 169.254.1.1
    --------------------------------------------
    Change to something like below

    auto lo eth0 eth0:1
    iface lo inet loopback
    iface eth0 inet static
    address xxx.xxx.xxx.xxx #original ip
    netmask 255.255.255.255
    broadcast 0.0.0.0
    up ip route replace 169.254.1.1 dev eth0
    up ip route add default via 169.254.1.1

    iface eth0:1 inet static
    address xxx.xxx.xxx.xxx
    netmask 255.255.255.255 #aditional IP
    broadcast 0.0.0.0

  • 5/16/2007 06:18:00 PM

    hi is possible to connect throuh public&privae-lan ip on same NIC

  • 6/01/2007 02:54:00 AM

    Yes, it is quite possible to use the same NIC card to connect to internet and local area network. In fact come used to call this `Poor Man's Router` back when routers were expensive, isong the built-in NAT/masquerade of the linux kernel to pose as a router with the rest of the lan and the internet comnection both connected to the same switch with the single NIC from the linux box.

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