Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Which spanning-tree port state listens for BPDUs and participates in STP, but does not learn MAC addresses yet?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Blocking
Blocking receives BPDUs but does not actively prepare to forward the way listening does in the transition sequence.
B
Best answer
Listening
Correct. Listening occurs before learning and forwarding.
C
Distractor review
Learning
Learning populates the MAC table; that is specifically what the question excludes.
D
Distractor review
Forwarding
Forwarding both learns and forwards traffic.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is confusing the listening and learning port states in STP. Many candidates incorrectly assume that MAC address learning begins during the listening state because it actively processes BPDUs and prepares for forwarding. However, the listening state strictly processes BPDUs and does not populate the MAC address table. Misunderstanding this can lead to incorrect answers, especially since the learning state is when MAC addresses are actually learned. Remembering that listening is a preparatory phase before learning helps avoid this common mistake.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is a Layer 2 protocol designed to prevent switching loops in Ethernet networks by selectively blocking redundant paths. STP ports transition through several states—blocking, listening, learning, and forwarding—to ensure a stable and loop-free topology. The listening state is a transitional phase where the port actively processes BPDUs to participate in STP topology decisions but does not yet learn MAC addresses or forward frames. This state allows the switch to confirm that no loops exist before allowing traffic to flow. During the listening state, the switch port listens for BPDUs from other switches to determine if it should transition to the learning state or revert to blocking. The port does not populate the MAC address table in this state, which prevents premature forwarding of frames that could cause loops. Once the port confirms that it is safe to forward traffic, it moves to the learning state, where it begins to populate the MAC address table with source addresses from received frames. This staged approach ensures network stability and loop prevention. A common exam trap is confusing the listening and learning states because both occur before forwarding. Candidates often mistakenly believe that MAC address learning starts in the listening state, but it actually begins in the learning state. Practically, this distinction prevents the switch from forwarding frames before the topology is stable, avoiding temporary loops. Understanding this behavior is essential for troubleshooting STP issues and correctly answering CCNA questions about port states.
KKey Concepts to Remember
- The Spanning Tree Protocol (STP) uses port states to prevent Layer 2 loops and ensure a loop-free topology in switched networks.
- The listening port state in STP processes Bridge Protocol Data Units (BPDUs) to participate in topology decisions without learning MAC addresses.
- In the listening state, a switch port prepares to transition to the learning state by determining if it should forward frames, but it does not populate the MAC address table yet.
- The blocking port state receives BPDUs but does not forward frames or learn MAC addresses, effectively preventing loops by blocking redundant paths.
- The learning port state populates the MAC address table by learning source MAC addresses from frames but does not forward frames yet.
- The forwarding port state both learns MAC addresses and forwards frames, allowing normal traffic flow in the network.
- STP port states follow a defined sequence: blocking → listening → learning → forwarding, with each state serving a specific role in loop prevention and topology convergence.
- Understanding the difference between listening and learning states is critical to avoid confusion about when MAC address learning begins during STP convergence.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
The Spanning Tree Protocol (STP) uses port states to prevent Layer 2 loops and ensure a loop-free topology in switched networks.
What is the correct answer to this question?
The correct answer is: Listening — In the classic 802.1D sequence, the listening state processes BPDUs and prepares for forwarding decisions, but it does not populate the MAC address table yet.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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