SPANNING TREE PROTOCOL || MODUL CISCO CCNA PART2 || MODUL 1

Introduction

This tutorial covers the Spanning Tree Protocol (STP), an essential network protocol used to prevent loops in Ethernet networks. Understanding STP is crucial for CCNA students and network professionals, as it ensures network reliability and efficiency. This guide will walk you through the key concepts and steps to configure and troubleshoot STP in Cisco devices.

Step 1: Understanding Spanning Tree Protocol

• Spanning Tree Protocol is designed to prevent loops in a network with redundant paths.
• It operates at Layer 2 of the OSI model.
• Key terms to know:
  • Bridge: A device that connects two or more network segments.
  • Root Bridge: The central switch in a spanning tree topology.
  • Bridge Protocol Data Units (BPDU): Messages exchanged between switches to maintain the spanning tree.

Step 2: Configuring Spanning Tree Protocol

1. Access the Switch CLI:

   • Connect to your Cisco switch using a console cable or SSH.

2. Enter Global Configuration Mode:

   • Use the command:

     enable
     configure terminal
     

3. Set the Spanning Tree Mode:

   • Use the command to set the desired mode (e.g., Rapid PVST or PVST):

     spanning-tree mode rapid-pvst
     

4. Identify and Set the Root Bridge:

   • Determine which switch will be the root bridge with the command:

     spanning-tree vlan [VLAN_ID] root primary
     

   • Replace [VLAN_ID] with the appropriate VLAN number.

5. Configure Bridge Priorities:

   • Adjust the bridge priority if necessary using:

     spanning-tree vlan [VLAN_ID] priority [value]
     

   • A lower value indicates a higher priority.

Step 3: Verifying the STP Configuration

• Use the following commands to verify STP status:
  • Check the STP status for a VLAN:

    show spanning-tree vlan [VLAN_ID]
    

  • Review the STP topology:

    show spanning-tree
    

Step 4: Troubleshooting Common STP Issues

• Looping Issues:

  • If loops are detected, ensure that the correct root bridge is set and that all switches are configured properly.

• Blocked Ports:

  • Use the command:

    show spanning-tree interface [interface_id]
    

  • This will help identify if any ports are in a blocking state and why.

• BPDU Issues:

  • Check for BPDU filtering or guard settings that might be preventing BPDU transmission:

    show running-config
    

Conclusion

In summary, the Spanning Tree Protocol is vital for maintaining loop-free networks. By understanding how to configure and troubleshoot STP, you can enhance your network's stability and performance. For further learning, consider exploring advanced STP concepts such as Multiple Spanning Tree Protocol (MSTP) or Rapid Spanning Tree Protocol (RSTP).