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7.2 | ![]() |
ISO Addressing | |
7.2.3 | ![]() |
ISO addressing with Cisco routers |
NETs and NSAPs are comprised
entirely of hexadecimal digits and must start and end on a byte
boundary. Cisco IOS interprets the NSAP address, from the right-hand end. The last byte is the NSEL and must be specified as a single-byte length preceded by a '.'. A NET definition must set the N-Selector to ’00’.
The preceding six bytes form the system ID. The IOS fixes this
length at six bytes. It is customary to code either a Media Access
Control (MAC) address from the router or an IP address, such as a loopback
address, into the system ID. With Integrated IS-IS, a loopback IP
address is commonly used for this purpose. In this case, the system ID
is obtained by converting a loopback address: 192.168.111.3 ->
192.168.111.003 -> 1921.6811.1003.
The rest of the address is treated by IOS as the area ID. The area
ID can be as small as one byte and as large as 13 bytes. It is
customary to use three bytes for the area ID field, with an AFI of
one byte such as the 47 in Figure
The following two examples illustrate the use of NSAP addresses with the Cisco IOS:
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