1.4 Building-Block Approach
1.4.6 Advantages of the building-block approach

As you have seen so far, the implementation of a building-block approach and hierarchical model has many advantages, including redundancy, scalability, loop-free topologies, fast convergence, and load balancing. The examples in Figures - illustrate these advantages.

In the sample network, we have two buildings that have an access switch on each floor and redundant connections to a distribution-layer switch. Each distribution-layer switch has redundant connections into the core of the network.

In Figure , notice the flow of traffic from switch M to switch P. Suppose there is a port failure in the access switch. Notice in Figure how the switch immediately chooses an alternate path. In Figure , suppose the link between the distribution switch and the core switch fails. As you can see, the switches will choose an alternate path through the core. In the following chapters you will learn how to configure these behaviors on the switch.