VLANs - Vlans allowed and active in management domain

Refer to the following sample output of the show interface trunk command on a Cisco IOS switch:

Port        Mode             Encapsulation  Status        Native vlan
Gi0/1       on               802.1q         trunking      1
Gi0/2       on               802.1q         trunking      1

Port        Vlans allowed on trunk
Gi0/1       1,20-30
Gi0/2       1-4094

Port        Vlans allowed and active in management domain
Gi0/1       1,20
Gi0/2       1,20

Port        Vlans in spanning tree forwarding state and not pruned
Gi0/1       1
Gi0/2       1
SW2(config)#

VLANs allowed on trunk - this shows the actual configuration that has been applied as far as allowed VLANs go. Whatever appears in the switchport trunk allowed vlan add command will appear here. If you don't issue this command, the default is 1-4094.

VLANS allowed and active in management domain - This lists those VLANs that are allowed on the trunk AND are currently active. What does it mean to be active? It simply means that the VLAN itself has been created. In other words, that VLAN must be listed in the output of the show vlan command.