NSAP Address Structure
In the Cisco implementation of integrated IS-IS, NSAP addresses have three
parts: the area ID, the system ID, and the NSEL. They are written in hexadecimal
and have a maximum size of 20 bytes.
�¡ Area IDs vary from 1 to 13 bytes. Those that begin with 49 designate
private area addressing.
�¡ The Cisco system ID must be exactly six bytes. MAC addresses or IP
addresses padded with 0s are often used as system IDs.
�¡ The NSEL is exactly one byte in size. A router always has a NSEL of 00.
Figure 4-2 shows the composition of an NSAP address.
Figure 4-2 IS-IS NSAP Address
CCNP BSCI
[ 44 ] CCNP BSCI Quick Reference
NSEL . 1
byte
System ID - Must be exactly 6
bytes long
Area ID - 1 to 13
bytes long
49.0234.0987.0000.2211.00