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see if a vlan is active

Posted on 2013-05-23
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Last Modified: 2013-06-07
I have hp procurve switches on my network, I am trying to cleanup my vlan. Is there a tool to see if a vlan is active or not? I can see if ports are active but how about vlan?


thanks
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Question by:officertango
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by:woolnoir
woolnoir earned 167 total points
ID: 39193082
When you say active... do you mean in use on ports, or do you mean with active traffic ?
The former is easy, configuration VLAN Configuration and you can see which ports are tagged and untagged with that VLAN.

If you mean traffic on the VLAN i'm not aware of any. Specifically what model of procurves do you have ?
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by:Don Johnston
Don Johnston earned 166 total points
ID: 39193086
"show vlan x" (where "x" is the vlan number in question)

If you have multiple switches, you will need to check all of them. If you don't see any untagged ports (and you aren't tagging to servers or routers), then it's probably unused.
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by:officertango
ID: 39193089
I would like to know which vlan is passing traffic, i know i can show port. I have HP procurve 5406.
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by:woolnoir
ID: 39193097
HP-Switch(Config)#show vlan (Shows vlan ID, Name, Status, Voice and Jumbo support)

HP-Switch(Config)#show vlan ports a1 (Shows the vlans belonging to a1)

HP-Switch(Config)#show vlan 1 (Shows ports that are assigned to vlan 1)
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Expert Comment

by:woolnoir
ID: 39193099
Give those a try, i'm more of a cisco guy - but i assume they will provide the information you require.
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by:Don Johnston
ID: 39193111
You could look at the port counters to see if any traffic is being passed on interfaces that are members of the VLAN.

Or you could create an ACL and apply it to the VLAN and check for any matches.

Other than that, I don't know of a command that will tell you if a VLAN is in use.
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by:Rick_O_Shay
ID: 39194171
It might help you to narrow things down by checking  for active entries for that VLAN/Subnet in  the ARP table on your router/L3 switch and MAC address tables in the L2 switches.

This will tell you if there are any stations currently using that VLAN.
Just remember it is no guarantee that there are not inactive stations that might use the VLAN that are just down right now.
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by:Don Johnston
ID: 39194194
A valid approach, but it would only show devices communicating with hosts on different VLANs.
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Rick_O_Shay earned 167 total points
ID: 39194463
Generally almost every host communicates with the Internet, even if not with other networks locally, so it is pretty likely there would be an ARP entry for any active devices.
And every currently active device has a mac entry in the switch's forwarding database which hopefully flags what VLAN it was learned in.
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