Electing the Root Bridge by Lowest Priority (SW2)

200-301 By islever Editorial Last updated

Interpret basic operations of Rapid PVST+ Spanning Tree Protocol

Short answer

B SW2 has the lowest bridge priority (4096), so it wins the root election regardless of MAC.

Question

Refer to the exhibit. Which switch in this configuration will be elected as the root bridge? SW1 0С:E4:85:71:03:80 - SW2 0С:0E:1A:22:05:97 - SW3 0C:E0:A1:1A:3C:9D - SW4 0С:00:18:A1:B3:19 - Exhibit: Electing the Root Bridge by Lowest Priority (SW2)
  1. SW1
  2. SW2 Correct Answer
  3. SW3
  4. SW4

Key Takeaways

When one switch has a strictly lower priority, it is root outright — MAC is only consulted on a priority tie.

STP elects the root by lowest bridge priority first. SW2's priority is 4096, lower than the other switches' priorities, so it becomes root without needing the MAC tiebreaker.

Common mistake: Picking the switch with the lowest MAC (e.g., SW4 0C:00:18...): priority is compared before MAC, and SW2's 4096 beats every other priority here.

Expert Analysis

Why the Answer Is Correct

B (SW2) is correct. SW2's bridge priority is 4096, the lowest in the exhibit, so it is elected root before any MAC comparison is needed.

Why the Other Options Are Wrong

A (SW1), C (SW3), and D (SW4) all have higher priorities than SW2's 4096, so they cannot win the root election.

Community Comment Notes

The vote is B (100). Commenters state SW2 has the lowest bridge priority (4096) and thus the lowest bridge ID.

Official Reference

https://learningnetwork.cisco.com/s/ccna-exam-topics

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Community Votes

B
100%

100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 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 5

  1. MicroDiff 👍 4 Answered B
    SW2 have the lowest bridge priority
  2. Rushit23 👍 2
    SW2 has the lowest bridge ID due to its lowest priority value of 4096.
  3. 3040636 👍 2
    SW2 correct ANs
  4. exiledwl 👍 1
    Sw2 just off of priority
  5. alexpeargentina 👍 1 Answered B
    SW 2 !!

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