Refer to The Exhibit. Which Switch Will be the Root Bridge After The Election Process is Complete?

The switch that will become the root bridge after the election process is the one with the lowest Bridge ID (BID), which consists of a configurable priority value (default 32768) and the switch's MAC address. If all switches have default settings, the one with the lowest MAC address wins. Administrators can influence the election by manually setting a lower priority value.

Tech Professionals

03 April 2025

Cisco

Refer to The Exhibit. Which Switch Will be the Root Bridge After The Election Process is Complete?

Introduction

In Cisco networking, the Spanning Tree Protocol (STP) plays a crucial role in preventing loops in a switched network while ensuring redundancy. One of the fundamental concepts in STP is the election of a Root Bridge, which acts as the reference point for all other switches in the network.

This article will explore how the Root Bridge election process works, analyze a given exhibit (scenario-based), determine which switch becomes the Root Bridge, and explain the key factors influencing this decision. Additionally, we will discuss the significance of this topic for the CCNA 2 v7 Checkpoint Exam and the Cisco 200-301 Certification. Finally, we will highlight how Study4Pass can help aspiring network engineers master these concepts effectively.

Understanding the Root Bridge Election Process

1. What is the Root Bridge?

The Root Bridge is the central switch in a Spanning Tree Protocol (STP) topology. All other switches (non-root bridges) calculate the shortest path to the Root Bridge to avoid loops while maintaining network connectivity.

2. How is the Root Bridge Elected?

The election process is based on the following criteria in order:

Lowest Bridge ID (BID) – The BID consists of:

Bridge Priority (default: 32768, configurable in multiples of 4096)
MAC Address (tiebreaker if priorities are equal)

Lowest Path Cost to the Root Bridge – If multiple switches have the same BID, the path cost (based on link speed) is considered.

Lowest Sender BID – If path costs are equal, the neighboring switch with the lowest BID is preferred.

Lowest Port ID – If all else is equal, the port with the lowest ID is chosen.

3. Default STP Behavior

If no switch is manually configured with a priority, the switch with the lowest MAC address becomes the Root Bridge.
Network administrators often manually set a preferred Root Bridge by lowering its priority (e.g., 4096).

Analyzing the Exhibit: Which Switch Becomes the Root Bridge?

(Note: Since we don’t have an actual exhibit, we will assume a common CCNA exam scenario.)

Sample Scenario:

Consider the following three switches in a network:

Switch	Priority	MAC Address
Switch A	32768	00:1A:2B:3C:4D:11
Switch B	28672	00:1A:2B:3C:4D:22
Switch C	32768	00:1A:2B:3C:4D:33

Election Process:

Compare Priorities:

Switch B has the lowest priority (28672), so it wins the election.
If priorities were equal (e.g., all 32768), the switch with the lowest MAC address (Switch A) would win.

Conclusion:

Switch B will be the Root Bridge because it has the lowest Bridge ID (priority + MAC).

Why is This Important for the CCNA 2 v7 and Cisco 200-301 Exam?

Understanding STP and Root Bridge election is critical for:
Preventing network loops while maintaining redundancy.

Optimizing traffic paths in a switched network.

Troubleshooting STP-related issues (e.g., suboptimal Root Bridge selection).

Common Exam Questions:

"Which switch becomes the Root Bridge if all have default priorities?"

Answer: The one with the lowest MAC address.

"How do you force a switch to become the Root Bridge?"

Answer: Lower its priority (spanning-tree vlan 1 priority 4096).

"What happens if the Root Bridge fails?"

Answer: A new election occurs, and the next best switch takes over.

How Study4Pass Help You Master STP and CCNA Concepts?

Study4Pass is a leading platform for IT certification preparation, offering:

Detailed CCNA 2 v7 Lab Solutions – Step-by-step explanations for STP configurations.
Real Exam Simulations – Practice questions mimicking Cisco’s style.
Interactive STP Demos – Visual learning aids for Root Bridge elections.
Expert Guidance – Tips from certified professionals to avoid common mistakes.

By leveraging Study4Pass, students gain confidence in tackling STP-related questions in the Cisco 200-301 exam and real-world networking scenarios.

Final Words

The Root Bridge election in STP is determined by the lowest Bridge ID (priority + MAC address). In our example, Switch B became the Root Bridge due to its lower priority. Mastering this concept is essential for the CCNA 2 v7 Checkpoint Exam and Cisco 200-301 Certification.

For in-depth tutorials, exam strategies, and hands-on labs, Study4Pass provides the best resources to ensure your success in networking certifications.