Area address attributes

The area-id command specifies the area address portion of the NET which is used to define the IS-IS area to which the router will belong. At least one area-id command should be configured on each router participating in IS-IS. A maximum of three area-id commands can be configured per router.

The area address identifies a point of connection to the network, such as a router interface, and is called a network service access point (NSAP). The routers in an area manage routing tables about destinations within the area. The Network Entity Title (NET) value is used to identify the IS-IS area to which the router belongs.

NSAP addresses are divided into three parts. Only the Area ID portion is configurable.

• Area ID

  A variable length field between 1 and 13 bytes. This includes the Authority and Format Identifier (AFI) as the most significant byte and the area ID.

• System ID

  A six-byte system identification. This value is not configurable. The system ID is derived from the system or router ID.

• Selector ID

  A one-byte selector identification that must contain zeros when configuring a NET. This value is not configurable. The selector ID is always 00.

The following is a sample of ISO addresses in IS-IS address format.