Cisco used the three-level Hierarchical Design Model for years. This older model provided a high-level idea of how a reliable network might be conceived, but it was largely conceptual because it didn’t provide specific guidance. Figure 1-1 shows the Hierarchical Design Model.
Figure 1-1. Hierarchical Design Model
Figure 1-2 is a simple drawing of how the three-layer model might have been built out. A distribution layer-3 switch is used for each building on campus, tying together the access switches on the floors. The core switches link the various buildings together.
Figure 1-2. Three-Layer ...