Extended System-ID on Switch

iworms

I tried turning off extended system-id on my 2950, and this is what it told me:

C2950_2(config)#no span ext s
% Command "no spanning-tree extend system-id <cr>" was not accepted.
  This platform requires that the extended system-id feature remain enabled.
C2950_2(config)#

What is the reason for always using extended id? Out of curiosity, what models would actually allow you to turn it off?

Netwurk

Cisco switches, depending on model, support either 64 or 1024 MAC addresses. The models that suppport 64 don't allow you to turn off the spantree system-id.

Here's a quote from a Cisco press book

"The total supply, or global resource, of MAC addresses for the switch is 1024 MAC addresses. However, not all Cisco switches have 1024 MAC addresses; some have only 64 MAC addresses. In addition to this total supply, there is space for one default MAC address per port to be secured. The total number of MAC addresses that can be specified per port is limited to the global resource of 1024 MAC addresses plus one default MAC address (per port)."

I think only the high-end switches (like a 7600) support 1024 MACs