IS-IS was not originally designed for IP routing. Some aspects of CLNP
routing, such as system IDs and area addresses, exist in the IP extension of IS-IS. The
IS-IS area address is required to identify the area in which the router participates.
Before you can configure the area address,
you must create the IS-IS routing process, which is also called
an area, using the following command:
To add an IS-IS area address to the router, use the
isis area area_name add area-address area_address
To delete an IS-IS area address from a router, use the
isis area area_name delete area-address area_address
software implementation of IS-IS
supports no more than three area addresses.