IS-IS (Intermediate System to Intermediate System) Protocol was developed as a OSI network protocol, not TCP/IP. So, normally IS-IS Protocol not uses IP address, but it uses NET (Network Entity Title) addresses. Let’s check this address issue a little.
In IS-IS Protocol, NSAP (Network Service Access Point) is used as network layer address. These addresses are assigned per node, not per interface.
And SNPA (Subnetwork Point of Attachment) is the Layer 2 addresses for IS-IS Protocol.
NSAP consist of three parts. These are:
Area address also has some parts inside it. These parts are AFI,IDI and HODSP.