How to see which VLANs are currently used on a trunkport on a switch?
Do a show mac address-table interface <interface>
and you will get a list of VLANs with MAC addresses used. Of course, any VLAN that have MAC-addresses associated, is in use.
That’s an easy way to find out which VLAN-tags are currently running over a trunk. (keep MAC-address aging timer in mind)