problem vlan.dat X match in dynamic trunking protocol

[chinpohpang851]

A-----B-----C

What happens when Switch A and C having vlan3 in database but vlan3 doesn't exist in Switch B? Switch B will drop the frames coming from both sides A & C with vlan3 tagging? I attached a photo for illustration.

[Milos Megis · Accepted solution]

Hi,
switch B will drop packets for VLAN 3.

Vlan 3 must be defined on switch B and allowed on trunks to switch A and C to ensure traffic for that VLAN.