Spanning Tree Loop Guard


For this lab you need REAL hardware. You can’t use switches in GNS3!

You need at least Catalyst 2950 switches for this lab.

The network agency corporation has hired you as a spanning tree specialist. One of their customers has issues with a switched network that only has fiber connections. Every now and then there’s a problem with the fiber and as a result layer 2 loops occur. It will take two months for the fiber company to check all cables/connectors so you want a temporary solution…


  • Configure SW1 so it is the root bridge for VLAN 1.
  • Configure your spanning-tree topology so the fa0/16 interface on SW3 becomes an alternate port.
  • Configure the fa0/16 interface on SW2 so it does not send or receive any BPDUs. This will cause a loop.
  • Configure all switches so this loop will be detected and SW3 will shut its fa0/16 interface.

It took me 1000s of hours reading books and doing labs, making mistakes over and over again until I mastered all the switch protocols for CCNP.

Would you like to be a master of switching too? In a short time without having to read 900 page books or google the answers to your questions and browsing through forums?

I collected all my knowledge and created a single ebook for you that has everything you need to know to become a master of switching.

You will learn all the secrets about spanning-tree, BPDUs, loop guard and more.

Does this sound interesting to you? Take a look here and let me show you how to Master CCNP SWITCH


Basic IOS for the switches should be sufficient. No special features needed.


Spanning Tree Loop Guard

Video Solution:

Configuration Files

You need to register to download the GNS3 topology file. (Registration is free!)

Once you are logged in you will find the configuration files right here.

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Do you want your CCNA or CCNP Certificate?

The How to Master series helps you to understand complex topics like spanning-tree, VLANs, trunks, OSPF, EIGRP, BGP and more.

Written by René Molenaar - CCIE #41726

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About the Author: Rene Molenaar

René - CCIE #41726 is the creator of where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on


  1. hello dear , thanks for u r hardworking , such it is really helpful tools for people
    how can i download this lab toplogy which is working with gns3

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