On the network of a customer I am working on the are 10-12 VLANs on most trunk ports on the main distribution between switches.

On most end point switches the ports are configured for multiple VLANs. Sometimes there is one untagged among those, sometimes not.

Expensive devices exist which you can connect to a switch port and they'll display all the VLAN information on that port.

I am pretty sure most of those devices run Linux. But then in a fancy enclosure with LCD screen and a price tag.

Is there a way I can connect my Linux box to a port and identify the VLANs which live on that port?

I know how to configure VLANs on my ethernet port, that is not the question.

jlinkels

If there is traffic on those VLANs, you can see it with
where NIC is the name of the computer's network interface connected to the port. Or use Wireshark (also on Windows).

I doubt there is a tool that allows you to see a VLAN while there is no traffic.

Usually I log into the switch to show config.