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find unused interfaces on switches

By hilko_bouwman ·
Hi all,

I'm a network administrator novice just finished school and started at my first job :) Please don?t flame me if I'm asking a very stupid/simple question... thx.

I trying to figure out which network interfaces are used on the switches and which ones aren't. I know there wall-outlets patched that are no longer in use. (I know this because nobody took care of the network before I came... only ad hoc actions). My idea is to measure/log traffic on each interface of the switch for a week and if there is no activity for a week, remove the patch. Which application can I best use for this situation... or are there better ways to solve this problem.

I'm also considering writing a python script to poll the switches via snmp...

All advice, ideas and suggestions are welcome.

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Your on the right track

by shawn In reply to find unused interfaces on ...


You're definately on the right track. I finished a 2 year project with EDS a year ogo that did exactly that. We had to monitor over 3000 LAN switches to determine unused ports and set them Admin Down. We began by monitoring each switch for a 3 week period, then we reported back to the customer our findings.

After 1 week if the customer didn't reply back with any concerns, the order went in, and a date was decided for when the ports of a particular switch was to be turned off.

The one thing I did that made all the firerence in the world, was to do the actual turn downs Durring Production hours. Why? Because Normal traffic would be on the port durring this time. If a port designated to be turned down belonged to someone on holiday durring the scan period, you'll see it when you check the switch that day.

Hope this help !

Shawn Lanthier

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Good lord.

by vince In reply to Your on the right track

Talk about taking things to the extreme. How many nodes in the network? How many switches? Are all switches, routers etc. centrally located? How is your network addressed, DHCP, statics, combination? Are they managed switches or dumb?

Don't meant to sound abraisive but I hate to see someone do more work than's necessary if I can help it.

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Das Blinkin Lights

by vince In reply to Good lord.

I'm sure you've already thought of this but i'll mention it just incase. Are there lights on the switches for link state?

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SNMP monitoring

by vince In reply to Das Blinkin Lights

You're on the right track with port monitoring though. But instead of writing your own you could just get MRTG or something simlar.

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Think of the end user !

by shawn In reply to Good lord.

I don't see any proposed solutions in your reply?? If you have experience, please share it?

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by vince In reply to Think of the end user !

I don't deal in the business of solutions without first examining the issues extensively. Consider this, lets say the questioner has 2 16 port switches at 60 percent capacity combined and that the 'end users' do not on a regular basis generate large ammounts of traffic for analysis. Sniffing ports for 1 month isn't really an option when you have someone to answer to and you can't honestly say you've done all the calculations and decided this is the best route to take. If he's working on a large enterprise network then yes, port monitoring may be the best way to go. But it most certainly isn't the only solution especially when you consider that not all networks are the same. I'll provide a solution when some of my questions are answered.

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some more info

by hilko_bouwman In reply to Good lord.

there are about 300-350 clients connected to the network. we have about 15 switches (cisco 2950, 3500). All equipment is located at the office/factory. clients get ip throught dhcp.

Like I told up front I'm a novice... what is the differents between a managed and dumb switch?

thanks for the help so far.

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