1.1 The Hierarchical Network Design Model
1.1.2 Router function in the hierarchy
Because each layer (core, distribution, and access) has a clearly defined function, each layer demands a different set of features from routers, switches, and links. Routers that operate in the same layer can be configured in a consistent way because they all must perform similar tasks. In fact, the router is the primary device that maintains logical and physical hierarchy in a network, so proper and consistent configurations are imperative. Cisco offers several router product lines, each with a particular set of features tailored for one of the three layers:
  • Core layer - 12000, 7500, 7200, and 7000 series routers -
  • Distribution layer - 4500, 4000, and 3600 series routers -
  • Access layer - 2600, 2500, 1700, and 1600 series routers -

The following sections revisit each layer and examine the specific routers and other devices used there.