At the end of an RSTP election process, which access layer switch port will assume the discarding role?

Refer to the exhibit.

At the end of an RSTP election process, which access layer switch port will assume the discarding role?
A . Switch3, port fa0/1
B . Switch3, port fa0/12
C . Switch4, port fa0/11
D . Switch4, port fa0/2
E . Switch3, port Gi0/1
F . Switch3, port Gi0/2

View Answer

Answer: C

Explanation:

In this question, we only care about the Access Layer switches (Switch3 & 4). Switch 3 has a lower bridge ID than Switch 4 (because the MAC of Switch3 is smaller than that of Switch4) so both ports of Switch3 will be in forwarding state. The alternative port will surely belong to Switch4.

Switch4 will need to block one of its ports to avoid a bridging loop between the two switches. But how does Switch4 select its blocked port? Well, the answer is based on the BPDUs it receives from Switch3.

A BPDU is superior than another if it has: