background image
The Cisco Hierarchical Model
21
we should perform certain functions. You would ask your boss, not your
subordinate, for a raise because of their positions in the business hierarchy.
The hierarchy requires that you ask someone at a higher level than yours.
Likewise, you can use tools like access lists at certain levels in hierarchical
networks and you must avoid them at others.
Let's face it, large networks can be extremely complicated, with multiple
protocols, detailed configurations, and diverse technologies. Hierarchy helps
us to summarize a complex collection of details into an understandable
model. Then, as specific configurations are needed, the model dictates the
appropriate manner for them to be applied.
Three-Layer Hierarchical Model
The Cisco hierarchical model is used to help you design a scalable, reliable,
cost-effective hierarchical internetwork. Cisco defines three layers of hierar-
chy, as shown in Figure 1.6, each with specific functionality.
F I G U R E 1 . 6
The Cisco hierarchical model
The three layers are as follows:
Core
Distribution
Access
Core
layer
Distribution
layer
Access
layer
Copyright ©2000 SYBEX , Inc., Alameda, CA
www.sybex.com