350-401 · Question #94
350-401 Question #94: Real Exam Question with Answer & Explanation
The correct answer is A: Enter spanning-tree port-priority 32 on SW1.. Spanning Tree Port Priority Explanation Option A is correct because *spanning-tree port-priority affects the upstream switch's decision, not the local switch. When SW2 wants its fiber port (G0/1) to be preferred, it must influence SW1's port priority on the corresponding Link2 in
Question
Refer to the exhibit. Link1 is a copper connection and Link2 is a fiber connection. The fiber port must be the primary port for all forwarding. The output of the show spanning-tree command on SW2 shows that the fiber port is blocked by spanning tree. An engineer enters the spanning-tree port-priority 32 command on G0/1 on SW2, but the port remains blocked. Which command should be entered on the ports that are connected to Link2 to resolve the issue?
Options
- AEnter spanning-tree port-priority 32 on SW1.
- BEnter spanning-tree port-priority 224 on SW1.
- CEnter spanning-tree port-priority 4 on SW2.
- DEnter spanning-tree port-priority 64 on SW2.
Explanation
Spanning Tree Port Priority Explanation
Option A is correct because spanning-tree port-priority affects the upstream switch's decision, not the local switch. When SW2 wants its fiber port (G0/1) to be preferred, it must influence SW1's port priority on the corresponding Link2 interface - SW1 is the one making the forwarding decision for that segment, so lowering the port priority on SW1's fiber-connected port makes SW1 prefer forwarding traffic through Link2, which unblocks SW2's fiber port.
Why the distractors are wrong:
- Option B enters a higher priority value (224) on SW1, which would make the fiber port less preferred, worsening the problem rather than fixing it.
- Option C suggests a port-priority of 4 on SW2, but the valid range for port priority is 0–240 in increments of 16, making 4 an invalid value.
- Option D enters priority 64 on SW2, but as established, the command must be applied on SW1 - changing the local port's priority does not resolve the upstream decision.
💡 Memory Tip: Think of port priority as a "vote cast by the neighbor." To influence which port gets chosen on your switch, the neighbor (upstream switch) must advertise a lower priority - so always apply port priority on the other end of the link you want preferred.
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