Check last activity on a Cisco switch interface

By PhilTkgh ·
I would like to check our Cisco switches for unused interfaces, including those that have cables plugged in but nothing attached to the end of them. The only way I know of doing it is to reset the counters to zero, leave it a few weeks, then check again and conclude that those whose counters are still zero are not in use.

Is there a way to establish immediately which are not in use, perhaps by looking at the last time a packet was transmitted or received on an interface or by obtaining the average over a period longer than the five minutes given by the "show interface" command?

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couple ideas

by gdeangelis In reply to Check last activity on a ...

You could just sho span to see what ports are forwarding, or sho int and determine which interfaces are down. You could then shut the already down suspected unused ports for a few days. I know this is not ideal, but your end user will let you know if they plug in and can't get on the network. I don't know how many switches/ports you are dealing with, but for a few here and there this will work.

If you have the gui enabled, you will see what ports are "lit up"

Alternatively, you could syslog port up/downs to a server and wade through that. Again, for a few switches, this will suffice.
Your idea of clearing and monitoring the counters is fine, and you can still sho int fa0/x a few times. You will see the port as down. Depending on your environment of course, a few days of being down would likely indicate the port isn't in use. If you keep a copy of the config handy and record anything you change, including cables you change, you can recover easily enough.

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