Chapter 12. Protecting against bridging loops by using the Spanning Tree Protocol
In the last chapter, you connected two switches—Switch1 and Switch2—via a single Ethernet connection. Imagine for a moment that both of these switches are in a live network and have dozens of end users connected to them. If the link between the switches goes down, devices on Switch1 won’t be able to communicate with devices on Switch2 and vice versa.
The solution is to add a redundant connection between FastEthernet0/23 on Switch1 and Switch2, as shown in figure 12.1. If the original link fails for whatever reason, the switches can communicate across the redundant link.