Which statement describes what happens when a port configured with root guard receives a superior BPDU?

Which statement describes what happens when a port configured with root guard receives a superior BPDU?
A . The port goes into errdisabled state and stops forwarding traffic.
B . The port goes into BPDU-inconsistent state and stops forwarding traffic.
C . The port goes into loop-inconsistent state and stops forwarding traffic.
D . The port goes into root-inconsistent state and stops forwarding traffic.

View Answer

Answer: D

Explanation:

The root guard ensures that the port on which root guard is enabled is the designated port. Normally, root bridge ports are all designated ports, unless two or more ports of the root bridge are connected together. If the bridge receives superior STP Bridge Protocol Data Units (BPDUs) on a root guard-enabled port, root guard moves this port to a root-inconsistent STP state. This root-inconsistent state is effectively equal to a listening state. No traffic is forwarded across this port. In this way, the root guard enforces the position of the root bridge.

Reference: http://www.cisco.com/en/US/tech/tk389/tk621/ technologies_tech_note09186a00800ae96b.shtml