By default, all VLANs are allowed across the trunk link. We can verify that using the show interfaces trunk command:
You can prevent traffic from certain VLANs from traversing a trunked link using the following interface mode command:
switchport trunk allowed vlan {add | all | except | remove} vlan-list
For example, to prevent traffic from VLAN 5 to traverse the trunk link, you can use the following command:
To verify that the traffic from VLAN 5 will indeed be blocked from traversing a trunked link, use the show interfaces trunk command again:
