Free CCNA | Analyzing STP | Day 20 Lab | CCNA 200-301 Complete Course

Introduction

In this tutorial, we will analyze Spanning Tree Protocol (STP) through a hands-on lab, as presented in Jeremy's IT Lab's "Free CCNA | Analyzing STP | Day 20 Lab." This guide will walk you through the key steps needed to calculate an STP topology and use the Command Line Interface (CLI) to analyze STP, which is essential for understanding network topology and preventing loops in a network.

Step 1: Turn off Link Lights

• Objective: Disable link lights on your devices to avoid confusion during analysis.
• How to do it:
  • Access your switch configurations.
  • Use the command to turn off link lights:

    interface [interface_id]
    no link-status
    

  • Replace [interface_id] with the specific interface you are configuring.

Step 2: Identify the Root Bridge

• Objective: Determine which switch is the root bridge in your STP topology.
• How to do it:
  • Use the following command in the CLI:

    show spanning-tree
    

  • Look for the line that states "Root ID" to identify the root bridge.
  • Note down the Bridge ID and the priority settings.

Step 3: Identify Root Ports

• Objective: Find out which ports are designated as root ports on non-root bridges.
• How to do it:
  • Again, use the command:

    show spanning-tree
    

  • Review the output for the "Root Port" information.
  • Ensure to note which port is the root port for each switch.

Step 4: Identify Designated and Non-Designated Ports

• Objective: Distinguish between designated and non-designated ports in the STP topology.
• How to do it:
  • Continue using:

    show spanning-tree
    

  • Look at the port roles listed in the output:
    • Designated ports will forward traffic.
    • Non-designated ports will block traffic.
  • Make a list of ports based on their roles.

Step 5: Confirm Using CLI

• Objective: Verify your findings with additional CLI commands.
• How to do it:
  • Use the command:

    show spanning-tree detail
    

  • This command provides deeper insights into port states, roles, and the overall STP topology.
  • Cross-reference your earlier findings to confirm accuracy.

Conclusion

In this tutorial, we covered the essential steps to analyze STP in your network environment. By turning off link lights, identifying the root bridge, root ports, and understanding designated vs. non-designated ports, you gain a solid grasp of STP functionality. For further practice, consider utilizing simulation tools like Boson NetSim or Packet Tracer to deepen your understanding of STP concepts in a controlled lab environment.