Refer to the exhibit. In the diagram, the switches are running IEEE 802.1s MST. Which ports are in the MST blocking state?
A.
GE-1/2 and GE 2/1
B.
GE-1/1 and GE-2/2
C.
GE-3/2 and GE 4/1
D.
no ports are in the blocking state
E.
There is not enough information to determine which ports are in the blocking state.
Explanation:
All these four switches are running MST and they are load-balancing. Dist-1 is the root bridge of VLANs 20 & 120 while Dist-2 is the root bridge of VLANs 40 & 140.
For VLANs 20, 120 switch Dist-1 is the root bridge so GE-4/1 & GE-4/2 links of Dist-2 are blocked:For VLANs 40, 140 switch Dist-2 is the root bridge so GE-3/1 & GE-3/2 links of Dist-1 are blocked:
But notice that there are no ports in blocking state although some ports are blocked for specific VLANs. Remember that the blocking state in MST switch means that the port is blocked for all VLANs.