What mechanism must be in use?

If a switch receives a superior BPDU and goes directly into a blocked state, what mechanism must be in use?
A. loop guard
B. root guard
C. EtherChannel guard
D. BPDU guard

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6 thoughts on “What mechanism must be in use?

  1. This is the trickiest question on the Sec exam.
    First it talks about “port blocking” which only BPDU guard (on access port) does and then talks about “superior BPDU received” which involves Root Guard configuration on the (trunk) port.

    Therefore we should pay attention to the fact that the port goes into a blocked state just because it received a BPDU, we don’t really care if it is a “superior” BPDU one or not.

    I would choose answer D.

  2. Its important to see that Cisco includes the word superior and root guard is used specifically to prevent superior BPDUs from changing the root bridge. There is controversy because root guard doesn’t use the word block in the terminology but it does ignores all traffic on the port until it stops sending the superior BPDUs. But with both of these things in mind, I think Cisco wouldn’t include the word superior BPDU if they didnt intend the answer to be root guard.

  3. I think the key is the word “Blocked”, therefore the correct answer is B, because BPDU Guard disables the port but Root Guard blocks the port.

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