IS-IS Protocol Addresses

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
– SystemID
– N-Selector

Area address also has some parts inside it. These parts are AFI,IDI and HODSP.

 

ISIS Address FormatAbove, we have checked an example ISIS address, 49.0115.125a.ab44.1234.11111.0123.abcd.aaaa.00. AS you can see, 49 is the AFI. 0115.125a.ab44.1234 is the IDI part. For Area Address, last part is HODSP and its value is 1111.