Information Technology Reference
In-Depth Information
With the complexities of network design, the CCDA needs to understand network models
used to simplify the design process. The hierarchical network model was one of the first
Cisco models that divided the network into core, distribution, and access layers.
The Cisco Enterprise Architecture model provides a functional modular approach to net-
work design. In addition to a hierarchy, modules are used to organize server farms, net-
work management, campus networks, WANs, and the Internet.
Hierarchical models enable you to design internetworks that use specialization of func-
tion combined with a hierarchical organization. Such a design simplifies the tasks required
to build a network that meets current requirements and can grow to meet future require-
ments. Hierarchical models use layers to simplify the tasks for internetworking. Each layer
can focus on specific functions, allowing you to choose the right systems and features for
each layer. Hierarchical models apply to both LAN and WAN design.
Key
To p i c
Benefits of the Hierarchical Model
The benefits of using hierarchical models for your network design include the following:
Cost savings
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Ease of understanding
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Modular network growth
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Improved fault isolation
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After adopting hierarchical design models, many organizations report cost savings be-
cause they are no longer trying to do everything in one routing or switching platform. The
model's modular nature enables appropriate use of bandwidth within each layer of the hi-
erarchy, reducing the provisioning of bandwidth in advance of actual need.
Keeping each design element simple and functionally focused facilitates ease of under-
standing, which helps control training and staff costs. You can distribute network moni-
toring and management reporting systems to the different layers of modular network
architectures, which also helps control management costs.
Hierarchical design facilitates changes. In a network design, modularity lets you create de-
sign elements that you can replicate as the network grows. As each element in the network
design requires change, the cost and complexity of making the upgrade are contained to a
small subset of the overall network. In large, flat network architectures, changes tend to
impact a large number of systems. Limited mesh topologies within a layer or component,
such as the campus core or backbone connecting central sites, retain value even in the hi-
erarchical design models.
Network managers can easily understand the transition points in the network, which helps
