Adding virtual network devices

Tue, 09/04/2012 - 16:57 -- jamie

If you have ever plugged a network cable into a computer, you are familiar with what a physical network interface is like.

Sometimes, it's useful to create "virtual" network interfaces. For example, if you are running multiple virtual servers on a single computer, each virtual server will need a virtual network interface in order to communicate with the network.

You can see a list of all your existing network interfaces with the ip link command:

ip link

Depending on how your computer is configured, you will usually see:

  • lo: this is the "loopback" adaptor - it's a virtual network interface that is automatically enabled on all computers.
  • eth0: this adaptor typically refers to your ethernet card - that you plug a network cable into for network access.
  • wlan0: this adaptor typically refers to your wireless access card

To add a new virtual network interface, type (replace "jamie" with your username):

sudo ip tuntap add dev tap0 mode tap user jamie

Now, re-run:

ip link

And you should see your device.

Before you can use it, you will need to set the state to UP.

sudo ip link set tap0 up

After re-running ip link, you may notice that it still says: "state DOWN"

That's because it's not yet in use.