Setting Up an Unnumbered Interface

An unnumbered interface does not have an IP address assigned to it. Unnumbered interfaces are often used in point-to-point connections where an IP address is not required.

You can set up an unnumbered interface using the ip unnumbered command. This command enables IP processing on an interface without assigning an explicit IP address to the interface.

You can supply an interface location, which is the type and number of another interface on which the router has an assigned IP address. This interface cannot be another unnumbered interface.

Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows. All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To set up an unnumbered interface:

• Issue the ip unnumbered command in Interface Configuration mode.
  host1(config-if)#ip unnumbered fastEthernet 0/0

  Use the no version to disable IP processing on an interface.