RSTP Discarding State Does Not Learn MAC Addresses
Short answer
B RSTP Discarding ports drop data frames and never update the MAC address table; learning starts only in the Learning state.
Question
Key Takeaways
It tests the split between frame dropping and MAC learning in RSTP port states; the trap is assuming any port receiving frames must update the MAC address table.
This H12-811 RSTP question tests whether a port in the Discarding state learns MAC addresses, and the answer is B (FALSE) because learning only begins in the Learning state.
Common mistake: Option A (TRUE) is chosen by assuming that because received frames reach the port, they populate the MAC address table — but Discarding explicitly disables learning, which happens only in Learning.
Expert Analysis
The two halves of the statement describe different port behaviours. The question hinges on the boundary between frame handling and MAC address learning on an RSTP port. An interface in the Discarding state does drop all received data frames so that no forwarding decisions are made from it — that part is correct. But RSTP explicitly forbids MAC address table updates from frames arriving on such a port.
Where learning is actually allowed. Learning only occurs in the Learning state (RSTP's equivalent of legacy STP's Learning state), where the port accepts received frames solely to populate the MAC address table while still not forwarding them. The Discarding state merges the old STP Blocking and Listening states: it suppresses forwarding and suppresses learning. So the clause "maintain the MAC address table based on received data frames" is false — received frames on a Discarding port leave the MAC address table untouched, and topology/BPDU processing, not data-driven learning, is what the port does.
Conclusion. Because the statement asserts an incorrect capability, the whole assertion is false: the correct option is B. This matches the community reasoning, which notes that "in the discarding state, although data frames are received, the MAC address table is not changed based on the oncoming frames" and that learning occurs only in the Learning state. Remember the RSTP progression Discarding → Learning → Forwarding, where learning begins exactly one state later.
Exam Strategy
When a statement has two clauses joined by "but" or "and", evaluate each clause independently — one false clause makes the whole statement FALSE. Apply the STP/RSTP state progression Discarding → Learning → Forwarding and ask, for each state, whether it forwards and whether it learns; only the Learning and Forwarding states learn, so any claim that a Discarding port learns is immediately false.
Frequently Asked Questions
Which RSTP states allow MAC address learning?
How does RSTP Discarding relate to classic STP states?
Why doesn't a Discarding port learn source MAC addresses?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 3 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 3
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konyuz 👍 1 Answered BB. FALSE. In RSTP, the Discarding state combines the functions of the STP Blocking and Listening states. A port in the discarding state discards all incoming data frames to prevent loops and does not learn MAC addresses. The purpose of this state is to ensure that a port does not participate in the active network topology until a loop-free path is confirmed. MAC address learning only occurs in the Learning and Forwarding states.
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Heidorn 👍 1 Answered BThis is false, in the discarding state, although data frames are received, the MAC address table is not changed based on the oncoming frames.
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Fmoura17 👍 1 Answered BThe correct answer is B. False. Explanation: In RSTP, an interface in the Discarding state:
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