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Example Network

Example Network

This chapter uses an example network to illustrate hardware configuration problems and configuration troubleshooting. The example network describes the most common connections you need to troubleshoot and enables you to apply your own enterprise network configuration to the examples.

Network Hierarchy

In a well-formed hierarchical network, there are three easily defined layers, traditionally referred to as the access, distribution, and core layers.

In an enterprise network, each layer provides different functions. Because these layers are not always recognized by their traditional names, the names have been modified to access or workgroup, distribution or policy, and core or backbone.

The access or workgroup layer connects users. Other functions of this layer are shared bandwidth, switched bandwidth, MAC-layer filtering, and micro segmentation. LAN switches, such as the Catalyst 5000 and Catalyst 5500 switches, exist most commonly in this layer of the network.

The distribution or policy layer performs the complex, CPU-intensive calculations such as filtering, access lists, inter-VLAN routing, Group Multicast Protocol (GMP), broadcast and multicast domain definition, and address or area aggregation. This layer might also contain the local servers. Routers, ATM switch routers, and sometimes LAN switches reside in the distribution layer.

The core or backbone layer is the backbone of the network. It is high-speed and concerned with quick traffic switching. It does not get involved in expensive packet manipulation. In the following example network, ATM connections function together as the core backbone, and Fast Ethernet and Gigabit Ethernet connections function together as the redundant backbone core. The central servers might also be attached to the high-speed backbone in the core. ATM switch routers, high-speed routers, and sometimes LAN switches can be found in the core.

Example Network

This section uses a fictitious network to describe actual problems in troubleshooting ATM switched networks.

Figure 3-1 provides a high level overview of the campus and remote networks.


Figure 3-1: Example Network Overview


The example network in Figure 3-1 has the following components:

Physical Connections

The example network contains the following physical connections:

Virtual Connections

The example network in Figure 3-2 has the following virtual connections:

Figure 3-2 shows the equipment overview of the example network, including the connection types of the network.


Figure 3-2: Equipment Overview of the Example Network


The engineering building in Figure 3-3 shows the following connections:


Figure 3-3: Engineering Building Connections

The typical Floor 1 wiring closet in Figure 3-4 shows the following connection examples:

Note Each Fast Ethernet distribution switch connection has a redundant link (See Figure 3-4.)

Figure 3-4: Typical Floor 1 Wiring Closet


The typical core switch router configuration in Figure 3-5 shows the following connections:


Figure 3-5: Typical Core Switch Router Configuration


The typical distribution switch router configuration in Figure 3-6 shows the following connections:


Figure 3-6: Typical Distribution Switch Router Configuration to Floor 1


The administration building configuration in Figure 3-7 shows the following connections:


Figure 3-7: Administration Building Connections



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Posted: Mon Dec 20 18:12:23 PST 1999
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