Layer 2 Redundancy
This section discusses some basics about Layer 2 redundancy design methods and Cisco solutions. Because STP and its operation and enhancements were already discussed in Chapters 3 and 4, they are not mentioned here.
A switch's SE contains two Gigabit Ethernet uplink interfaces. Cisco assumes that you'll use these interfaces to connect to a switch at either a higher or lower layer in Cisco's three-layer hierarchy: core, distribution, and access. Of course, you can connect anything you want to these interfaces. However, you do have to take care of setting up redundant connections between a higher and lower layer.
For example, let's look at the right side of Figure 7.1, where there are redundant connections between ...