CCNA Cisco Certified Network Associate Study Guide - FTP Server

The Cisco Three-Layer Hierarchical Model 33
for instance, hierarchy dictates that you ask your boss, not your subordinate.
That is the person whose role it is to grant (or deny) your request.
Hierarchy has many of the same benefits in network design that it does in
other areas of life. When used properly, it makes networks more predictable.
It helps us define at which levels of hierarchy we should perform certain
functions. Likewise, you can use tools such as access lists at certain levels in
hierarchical networks and 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 summarize a complex collection of details into an understandable model.
Then, as specific configurations are needed, the model dictates the appropriate
manner to apply them.
The Cisco hierarchical model can help you design, implement, and maintain
a scalable, reliable, cost-effective hierarchical internetwork. Cisco defines
three layers of hierarchy, as shown in Figure 1.14, each with specific functions.
FIGURE 1.14 The Cisco hierarchical model
Core
layer
Distribution
layer
Access
layer
The following are the three layers:
� The Core layer
� The Distribution layer
� The Access layer