The answer is that the trunk link between SW1 and SW2 is down. This is correct because when a switch stops receiving superior BPDUs from the designated root bridge, it elects itself as the new root. In the output, SW2 shows its own Bridge ID matching the Root ID and states “This bridge is the root,” with no root port listed—a clear sign that no BPDUs are arriving from SW1. On the CCNA 200-301 v2 exam, this scenario tests your understanding that a root bridge election is driven entirely by BPDU propagation; a down trunk link isolates a switch, forcing it to claim root. A common trap is assuming a configuration error or priority mismatch, but the absence of a root port is the dead giveaway. Remember the mnemonic: “No BPDU, no root port—you become the root.”
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
SW2# show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000a.f3e5.1234
This bridge is the root
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000a.f3e5.1234
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Refer to the exhibit. A network engineer expects SW1 to be the root bridge for VLAN 1, but the show spanning-tree vlan 1 output on SW2 shows that SW2 is the root. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
SW2# show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000a.f3e5.1234
This bridge is the root
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000a.f3e5.1234
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
A
SW1 is configured with a priority of 32769 but has a higher MAC address than SW2.
Why wrong: Even if SW1 had a higher MAC, SW2 would still see SW1 as the root if the link were up, and SW2 would have a root port. The output shows no root port, proving SW2 is not receiving any BPDUs, not that a tiebreaker is making it root.
B
Spanning tree is disabled on SW1 for VLAN 1.
Why wrong: While disabled STP on SW1 would prevent BPDUs, the scenario states that SW1 should be the root, implying STP is active and properly configured. A physical link failure is a more likely cause than a deliberate misconfiguration in this context.
C
SW1 has a bridge priority of 4096, but BPDU guard is configured on SW2's port to SW1, causing the port to be err-disabled.
Why wrong: If BPDU guard had triggered, the port would be err-disabled and would not appear in the spanning-tree table as designated or root. However, the output simply omits any interface to SW1, which is equally consistent with a down link. No evidence in the exhibit points to BPDU guard, making a physical link problem the most straightforward cause.
D
The trunk link between SW1 and SW2 is down.
The missing root port and the fact that SW2 sees itself as root confirm that SW2 is not receiving any BPDUs from SW1. This is exactly the behavior when the inter-switch trunk is physically down, breaking the spanning-tree topology.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The trunk link between SW1 and SW2 is down.
SW2 shows itself as the root (Root ID and Bridge ID are identical, and the text 'This bridge is the root'), and there is no root port listed. In a stable spanning-tree topology, a non-root switch must have a root port to reach the root. The absence of any root port indicates that SW2 is not receiving superior BPDUs from SW1. The most likely cause is that the trunk link between SW1 and SW2 is down, preventing BPDU exchange.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
SW1 is configured with a priority of 32769 but has a higher MAC address than SW2.
Why it's wrong here
Even if SW1 had a higher MAC, SW2 would still see SW1 as the root if the link were up, and SW2 would have a root port. The output shows no root port, proving SW2 is not receiving any BPDUs, not that a tiebreaker is making it root.
✗
Spanning tree is disabled on SW1 for VLAN 1.
Why it's wrong here
While disabled STP on SW1 would prevent BPDUs, the scenario states that SW1 should be the root, implying STP is active and properly configured. A physical link failure is a more likely cause than a deliberate misconfiguration in this context.
✗
SW1 has a bridge priority of 4096, but BPDU guard is configured on SW2's port to SW1, causing the port to be err-disabled.
Why it's wrong here
If BPDU guard had triggered, the port would be err-disabled and would not appear in the spanning-tree table as designated or root. However, the output simply omits any interface to SW1, which is equally consistent with a down link. No evidence in the exhibit points to BPDU guard, making a physical link problem the most straightforward cause.
✓
The trunk link between SW1 and SW2 is down.
Why this is correct
The missing root port and the fact that SW2 sees itself as root confirm that SW2 is not receiving any BPDUs from SW1. This is exactly the behavior when the inter-switch trunk is physically down, breaking the spanning-tree topology.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The trunk link between SW1 and SW2 is down.Correct answer▾
Why this is correct
The missing root port and the fact that SW2 sees itself as root confirm that SW2 is not receiving any BPDUs from SW1. This is exactly the behavior when the inter-switch trunk is physically down, breaking the spanning-tree topology.
✗SW1 is configured with a priority of 32769 but has a higher MAC address than SW2.Wrong answer — click to see why▾
Why this is wrong here
Candidates focus on the matching priority numbers and overlook the missing root port that indicates a complete loss of BPDUs.
✗Spanning tree is disabled on SW1 for VLAN 1.Wrong answer — click to see why▾
Why this is wrong here
Candidates may assume no BPDUs means STP is off, but the intended root designation suggests STP is on and a physical disconnect is the primary suspect.
✗SW1 has a bridge priority of 4096, but BPDU guard is configured on SW2's port to SW1, causing the port to be err-disabled.Wrong answer — click to see why▾
Why this is wrong here
Candidates recall that BPDU guard can block ports, but they fail to differentiate between a missing port due to err-disable and a missing port due to a physically down link, which looks identical in this output.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
Even if SW1 had a higher MAC, SW2 would still see SW1 as the root if the link were up, and SW2 would have a root port. The output shows no root port, proving SW2 is not receiving any BPDUs, not that a tiebreaker is making it root.
Scenario analysis trap
While disabled STP on SW1 would prevent BPDUs, the scenario states that SW1 should be the root, implying STP is active and properly configured. A physical link failure is a more likely cause than a deliberate misconfiguration in this context.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Switching and Network Access — This question tests Switching and Network Access — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The trunk link between SW1 and SW2 is down. — SW2 shows itself as the root (Root ID and Bridge ID are identical, and the text 'This bridge is the root'), and there is no root port listed. In a stable spanning-tree topology, a non-root switch must have a root port to reach the root. The absence of any root port indicates that SW2 is not receiving superior BPDUs from SW1. The most likely cause is that the trunk link between SW1 and SW2 is down, preventing BPDU exchange.
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.