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Community Member

What VLANs are on a trunk

I have been provided a network connection that I know has two VLANs on it.  One is a private link for which I know the VLAN ID.

The second carries the internet and I cannot remember the VLAN ID can query the trunk port to find what other VLANs are on it.

My switch is only set up for the one VLAN, so cant just use a show run.


What VLANs are on a trunk

Hi Martin,

If you know the interface number on which trunk is made, then issue the below command

show interface switchport



What VLANs are on a trunk

You could just run 'show interface trunk'. This will show you all trunks on the local switch and what VLANs are currently active on the trunk.

Community Member

What VLANs are on a trunk

thanks for your reply either they are sending almost every VLAN down that cable or it didn't work.

What VLANs are on a trunk

Can you give me a brief description of your topology?

Does this switch have a cable going out to the internet and the same switch has a cable going internally to your network?


Re: What VLANs are on a trunk

Hi Martin,

Are you saying that you have no access to the other end of the link, and that you have lost the proper config to put on your end?

If this is the case, you can simply put a ptocol analyser (e.g Wireshark) on the cable ( or SPAN the port) and look for the dot1q tags on the packets you're recieving.


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