Table of Contents

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.

This chapter contains the following sections:

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 6000 family of 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, switch routers, and occasionally 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. Switch routers, high-speed routers, and occasionally LAN switches can be found in the core.

Example Networks

This section includes the following example networks:

Example ATM Network

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

Figure 4-1 provides a high level overview of the campus and remote networks.

The example network in Figure 4-1 has the following components:

Physical Connections

The example network contains the following physical connections:

Virtual Connections

The example network in Figure 4-2 has the following virtual connections:

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

The engineering building in Figure 4-3 shows the following connections:

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

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

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The typical core switch router configuration in Figure 4-5 shows the following connections:

The typical distribution switch router configuration in Figure 4-6 shows the following connections:

The administration building configuration in Figure 4-7 shows the following connections:

Example Mixed ATM and Layer 3 Network

This section uses the fictitious network described in the "Example ATM Network" section to illustrate actual problems in troubleshooting a mixed ATM and Layer 3 switched network.

While the example network overview is the same as shown in Figure 4-1, there are additional redundant Layer 3 Gigabit Ethernet connections between buildings, LAN switches, and some high-usage servers. These redundant Gigabit Ethernet and Gigabit EtherChannel provide the high-capacity trunks needed to connect these gigabit switches if the primary ATM connections should fail.

Physical Connections

The example network contains the following physical connections:

Virtual Connections

The example network in Figure 4-8 has the following virtual connections:

Figure 4-8 shows the equipment overview of the example network, including the connection types of the network.

The engineering building in Figure 4-9 shows the following connections:

The typical Floor 1 wiring closet in Figure 4-10 shows the following connection examples:

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Note    Each Gigabit Ethernet distribution switch connection has a redundant link. See Figure 4-10.

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The typical core switch router configuration in Figure 4-11 shows the following connections:

The typical distribution switch router configuration in Figure 4-12 shows the following connections:

The administration building configuration in Figure 4-13 shows the following connections: