CCNA Switching and Network Access Practice Question
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 P2pRefer 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?
⚠ Common exam trap
Cisco often tests the misconception that a lower priority always guarantees root bridge status, but the trap here is that a failed link prevents BPDU exchange, causing the switch with the higher bridge ID to become root by default.
Answer choices
Why each option matters
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.
If the trunk link between SW1 and SW2 is down, SW2 will not receive BPDUs from SW1. Without BPDUs, SW2 assumes it is the root bridge for VLAN 1 (since every switch defaults to root for its own VLANs). This explains why SW2's show spanning-tree output shows itself as root, even if SW1 has a lower bridge priority.
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.
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?”
Visual reference
Go deeper
Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
VLAN
A VLAN logically segments a physical network into isolated broadcast domains without requiring separate physical switches.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
About these practice questions
This 200-301 question is part of Courseiva's 1,389-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.