Catalyst 2960 Unsupported Commands Still Work?

Posted on in Networking

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This is a bit of random oddness I stumbled upon this morning.

I was working on a Cisco Catalyst 2960 switch and needed to know which MAC addresses the device had learned on a particular interface. The usual way to do this is with the show mac-address-table interface command. While I was typing I hit the ? to get additional option information. This is the response I got back from the CLI:

% Unrecognized command

I use this command at least three times a week, so I'm pretty sure it's "recognized". The show mac-address-table command is definitely not on the list of show commands the CLI claims are available. On a lark, I went ahead and executed show mac-address-table and IOS was kind enough to return the 1,627 MAC addresses this switch had learned. Bizarre.

According to the Cisco documentation for Cisco IOS Release 12.2(40)SE, the show mac-address-table command is on the list of commands that "appear when you enter the question mark (?) at the Catalyst 2960 switch prompt but are not supported".

Interestingly enough, that's the exact opposite of the behavior displayed by the device!

At this point, I'm willing to chalk it up to random morning oddness and move on.

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