In a switched networked environment, which currently dominates enterprise business, we need to provide a quick converging, and loop free layer 2 network. This involves understanding Spanning Tree Protocol, which is a simple solution to prevent layer 2 loops, yet can create complex topologies, and potentially a slow converging network, which can cause issues for our users. We will look at how Spanning Tree Protocol operates, and then examine how it converges on a real network. Then we dive into looking at how we can modify the Spanning Tree Protocol topology, and improve performance. Additionally in this series, we will perform an IOS upgrade on a router and a switch, and even cover how to fix an upgrade gone really bad. Also, you will learn how to change the password on a router or switch, when you do not know the password.