The network manager has requested that several new VLANs (VLAN 10, 20, and 30) are allowed
to traverse the switch trunk interface. After the command switchport trunk allowed vlan 10,20,30 is
issued, all other existing VLANs no longer pass traffic over the trunk. What is the root cause of the
problem?

A.
The command effectively removed all other working VLANs and replaced them with the new
VLANs.

B.
VTP pruning removed all unused VLANs.

C.
ISL was unable to encapsulate more than the already permitted VLANs across the trunk.

D.
Allowing additional VLANs across the trunk introduced a loop in the network.