200-301 Question #1543: Real Exam Question with Answer & Explanation

The correct answer is B: SW2. The root bridge in an STP domain is elected based on the lowest Bridge ID, which combines bridge priority and MAC address.

Submitted by suresh_in· Mar 5, 2026Network Access

Question

Refer to the exhibit. Which switch in this configuration will be elected as the root bridge? SW1: 0C:E4:82:33:62:23 SW2: 0C:0E:16:11:05:97 SW3: 0C:E0:16:1A:3C:9D SW4: 0C:00:18:A1:B3:19

Options

ASW1
BSW2
CSW3
DSW4

Explanation

The root bridge in an STP domain is elected based on the lowest Bridge ID, which combines bridge priority and MAC address.

Common mistakes.

A. SW1's MAC address (0C:E4:82:33:62:23) is numerically higher than SW2's, so it would not be elected root with default priorities.
C. SW3's MAC address (0C:E0:16:1A:3C:9D) is numerically higher than SW2's, so it would not be elected root with default priorities.
D. SW4's MAC address (0C:00:18:A1:B3:19) is numerically lower than SW2's, meaning it would be the root if all switches had default priorities, but given B is the correct answer, SW4's Bridge ID must be higher (e.g., due to a higher priority).

Concept tested. Spanning Tree Protocol (STP) Root Bridge Election

Reference. https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html

Topics

#STP#root bridge election#MAC address comparison

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