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Cisco Networking Academy Connecting Networks Companion Guide: Hierarchical Network Design

Chapter Description

This chapter introduces network design concepts, principles, models, and architectures. It covers the benefits that are obtained by using a systematic design approach.

Cisco Enterprise Architecture (1.2)

The Cisco Enterprise Architecture is a modular approach to network design. This section identifies enterprise architecture modules that are commonly found in medium-to-large organizations.

Modular Design (1.2.1.1)

While the hierarchical network design works well within the campus infrastructure, networks have expanded beyond these borders. As shown in Figure 1-9, networks have become more sophisticated and complex. The central campus site now requires connections to branch sites and support for teleworking employees working from home offices or other remote locations. Large organizations may also require dedicated connections to offsite data centers.

Figure 1-9

Figure 1-9 Expanding Beyond the Campus Infrastructure

As the complexity of the network increased to meet these demands, it became necessary to adjust the network design to one that uses a more modular approach.

A modular network design separates the network into various functional network modules, each targeting a specific place or purpose in the network. The modules represent areas that have different physical or logical connectivity. They designate where different functions occur in the network. Using a modular approach has several benefits, including

  • Failures that occur within a module can be isolated from the remainder of the network, providing for simpler problem detection and higher overall system availability.
  • Network changes, upgrades, or the introduction of new services can be made in a controlled and staged fashion, allowing greater flexibility in the maintenance and operation of the campus network.
  • When a specific module no longer has sufficient capacity or is missing a new function or service, it can be updated or replaced by another module that has the same structural role in the overall hierarchical design.
  • Security can be implemented on a modular basis allowing for more granular security control.

The use of modules in network design enables flexibility and facilitates implementation and troubleshooting.

Modules in the Enterprise Architecture (1.2.1.2)

A modular approach to network design further divides the three-layer hierarchical design by pulling out specific blocks or modular areas. These basic modules are connected together via the core of the network.

Basic network modules include

  • Access-distribution: Also called the distribution block, this is the most familiar element and fundamental component of a campus design (see Figure 1-10).

    Figure 1-10

    Figure 1-10 Access-Distribution Module

  • Services: This is a generic block used to identify services such as centralized Lightweight Access Point Protocol (LWAPP) wireless controllers, unified communications services, policy gateways, and more (see Figure 1-11).

    Figure 1-11

    Figure 1-11 Services Module

  • Data center: Originally called the server farm. This block is responsible for managing and maintaining many data systems that are vital to modern business operations. Employees, partners, and customers rely on data and resources in the data center to effectively create, collaborate, and interact (see Figure 1-12).

    Figure 1-12

    Figure 1-12 Data Center Module

  • Enterprise edge: Consists of the Internet edge and the WAN edge. These blocks offer connectivity to voice, video, and data services outside the enterprise (see Figure 1-13).

    Figure 1-13

    Figure 1-13 Enterprise Edge Module

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