The Hierarchical Design Model
Cisco has 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 did not provide specific
guidance. Figure 1-1 is a simple drawing of how the three-layer model might
have been built out. A distribution layer-3 switch would be used for each
building on campus, tying together the access-switches on the floors. The
core switches would link the various buildings together.