Finding unused ports

Answered Question
Nov 27th, 2007

In one of our buildings we have a number of 4500 switches to provide LAN connectivity to users and we are running out of ports. Rather then buying more blades or switches I would like to reuse some ports. So my question is how to tell if a port has not been used in say 4 weeks (to allow for vacations)?

I had thought of clearing the counters and then just coming back in 4 weeks and looking through them but we are talking about 6 4500s with 5 48 port blades in each, that's 1440 ports!

Any suggestions would be appreciated.

I have this problem too.
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Correct Answer by smodonnell about 9 years 1 month ago

You might try this. We find it very useful to find unused ports:

'show int link' to show the downtime for each interface

or

'show int link | inc 168' to show the interfaces that have been down for a week (24x7) which you can extrapolate out to suit your needs.

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Edison Ortiz Tue, 11/27/2007 - 11:45

Without a Network Management tool, that's the only way to find out port inactivity (clearing out the counters and inspecting them after 4 weeks).

You can be a little creative with the show interface command and only show the input/output lines. Copy and paste this output onto a text editor and do search for 0 value.

craig.siemens Tue, 11/27/2007 - 12:17

That's what I was afraid of, unfortunately we are 'transitioning' to a new management tool and the transition period is starting to feel like permanence.

Correct Answer
smodonnell Tue, 11/27/2007 - 16:41

You might try this. We find it very useful to find unused ports:

'show int link' to show the downtime for each interface

or

'show int link | inc 168' to show the interfaces that have been down for a week (24x7) which you can extrapolate out to suit your needs.

glen.grant Tue, 11/27/2007 - 16:45

smodoneel is correct , a show interface link command will show you how long a port has been down so if you have a port that has been down 2 or 3 months if the switch hasn't gone down in that period you can probably surmise the port is not being used . The weird thing is i think only the 4500's have this command and not other IOS devices , it would be usueful occasionally on all switches.

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