Tracking down unused vlans

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Mar 11th, 2010
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I am trying to clean up a configuration on a 6500 that has 30+ vlans defined.  I am certain most of these are not in use any longer, but I would like to make sure before I go deleting them from the vlan database. The problem is that the native vlan is trunked all over the place, so I have no real way of telling which vlans are really in use and which ones are not.  Can anyone give me some suggestions about how to track this mess?


Thanks!

-J

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Jon Marshall Thu, 03/11/2010 - 12:27
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millerjw wrote:


I am trying to clean up a configuration on a 6500 that has 30+ vlans defined.  I am certain most of these are not in use any longer, but I would like to make sure before I go deleting them from the vlan database. The problem is that the native vlan is trunked all over the place, so I have no real way of telling which vlans are really in use and which ones are not.  Can anyone give me some suggestions about how to track this mess?


Thanks!

-J


J


Catalysts keep per-vlan mac-address tables so i would start with that ie. "sh mac-address-table vlan " to see if you have any active mac-addresses in that vlan.


You could also enable VTP pruning to see which vlans are pruned off the trunks links and where it at all the vlans are in use.


Not sure what your point about the native vlan is ?


Jon

burleyman Thu, 03/11/2010 - 12:39
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You could also scan for IP Addresses in the range for the VLAN's and see if any respond back. Also if you have DHCP scopes setup for any of the VLAN's you could see if there are any resent leases.



Jon, Thanks for that command, I did not now about that one. 5+





Mike

Leo Laohoo Thu, 03/11/2010 - 13:12
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What I normally use is the combo of "sh vlans" and "sh interface trunks".  In the "sh vlans" I would look at VLANs that doesn't have ports assigned to them.  I would corolate them with the "sh interface trunks".  If it's not there either then I delete it. If you are using VTP Server/Client, remember to do your changes on the Server.

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