Hello, everyone.
Cisco documentation completely omits the IDP part of the NET.
The NET may be 8 to 20 octets in length and consists of three parts
Apparently, the Area address an be 1 to 13 bytes in length. The Sys-ID Is 6 bytes and the NSEL is 1 byte. This together creates 20 bytes.
There doesn’t appear to be any space for IDP. Even if I configure a NET address that uses it, such as:
It includes the AFI and IDI in the area address. Does Cisco ignore or not recognize the first two? Or are they used so little that they decided to completely omit it?
A Cisco Live presentation says this:
IS-IS Addressing - Sample NET Addresses
8-byte Area ID / System ID
Area Address Station ID SEL ┌──────────┐ ┌──────────────┐ ┌──┐ 07 .1921.6800.1001 .00 └──────────┘ └──────────────┘ └──┘ Area
- Area Address: 07
- Station ID (System ID): 1921.6800.1001
- SEL (NSEL): 00
10-byte Private AFI / Area ID / System ID
Area Address ┌──┬──────┐ ┌──────────────┐ ┌──┐ 49 .1234 .1921.6800.1001 .00 └──┴──────┘ └──────────────┘ └──┘ AFI Area Station ID SEL
- AFI: 49 (Private)
- Area ID: 1234
- Station ID (System ID): 1921.6800.1001
- SEL (NSEL): 00
OSI NSAP Format
Area Address ┌──┬────┬──────┐ ┌──────────────┐ ┌──┐ 49 .0456 .1234 .1921.6800.1001 .00 └──┴────┴──────┘ └──────────────┘ └──┘ AFI Domain Area Station ID SEL
- AFI: 49
- Domain (IDI): 0456
- Area (HODSP): 1234
- Station ID (System ID): 1921.6800.1001
- SEL (NSEL): 00
Apparently, the Area Address consists of the AFI, IDI, and the Area number.. So the area address is not the same as the area or is it? I’ve tried changing the AFI or Domain while keeping the Area number the same and the routers formed only a L2 adjacency so I don’t think they considered the area to be the same 
Thank you
David