Refer to the exhibit.
The output that is shown is generated at a switch. Which three statements are true? (Choose three.)
A.
All ports will be in a state of discarding, learning, or forwarding.
B.
Thirty VLANs have been configured on this switch.
C.
The bridge priority is lower than the default value for spanning tree.
D.
All interfaces that are shown are on shared media.
E.
All designated ports are in a forwarding state.
F.
This switch must be the root bridge for all VLANs on this switch.
Explanation:
From the output, we see that all ports are in Designated role (forwarding state) -> A and E are
correct. The command “show spanning-tree vlan 30 only shows us information about VLAN 30. We
don’t know how many VLAN exists in this switch -> B is not correct. The bridge priority of this switch
is 24606 which is lower than the default value bridge priority 32768 -> C is correct. All three
interfaces on this switch have the connection type “p2p”, which means Point-to-point environment
– not a shared media -> D is not correct. The only thing we can specify is this switch is the root
bridge for VLAN 3o but we can not guarantee it is also the root bridge for other VLANs -> F is not
correct.
I have a disagreement with this question.
The root bridge will NEVER have a port in blocking/listening/learning mode. All ports on a root switch will always be forwarding. If there are any ports that are blocked they are certainly not blocked at the root switch, they will be blocked at another switch down the “tree.”
This is from the Cisco document which outlines STP technologies ;
STP Rule 1—All ports of the root switch must be in forwarding mode.
Important word in option A is *OR*, which makes option A completely valid
I think they are basing the answer on the protocol being used. RSTP. Which only has those three states, not that they are actually being used on the root bridge.