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Assembling and Cabling Cisco Devices

   

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Assembling and Cabling Cisco Devices

  

 

Cabling the LAN

  

 

Cabling the WAN

  

 

Setting Up Console Connections to Cisco Devices

  

 

Summary

  

 

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Interconnecting Cisco Network Devices

From: Interconnecting Cisco Network Devices
Author: Stephen McQuerry
Publisher: Cisco Press (53)
More Information

2. Assembling and Cabling Cisco Devices

Upon completion of this chapter, you will be able to perform the following tasks:

  • Identify and connect the necessary components to provide connectivity between switches and routers.

  • Determine what components are necessary to enable WAN connectivity over serial or ISDN BRI connections for a Cisco router.

  • Set up console connectivity to Cisco routers and switches to provide configuration and monitoring of these devices.

  • Determine the need for differing cable types and topologies in a network environment.

The focus of this book is on the installation and configuration of Cisco devices. Although many configuration parameters and services are common across most Cisco products, this book focuses on lower-end products such as the 1600, 2600, 4000, and 3600 series of products and the 1900 and 2820 series of switches. In this chapter, you learn how to cable your Cisco devices to provide connectivity for devices in your network and how to configure your Cisco device.

Cabling the LAN

Interconnection of network devices takes place through the structured cabling of the local-area network (LAN) and wide-area network (WAN). Figure 2-1 illustrates the interconnection of devices via the structured cabling of the network.

Figure 2-1. Network Cabling

The following sections examine these aspects of cabling the LAN:

LAN Physical Layer Implementations

The cabling aspect of the LAN exists at Layer 1 of the OSI reference model. Many topologies support LANs and many different physical media. This book focuses on Ethernet as the physical and data link connections for many of the LAN connections; thus, much of this section deals with the physical aspects of that topology. Figure 2-2 shows a subset of physical layer implementations that can be deployed to support Ethernet.

Figure 2-2. Ethernet: LAN Implementations

The term Ethernet refers to a family of LAN implementations. Physical layer implementations vary, and all support various media types, as shown in Figure 2-2. The following list documents the three principal categories:

  • Ethernet (DIX) and IEEE 802.3—LAN specifications that operate at 10 Mbps over coaxial cable, UTP, or fiber.

  • 100 Mbps Ethernet (IEEE 802.3u)—LAN specification known as Fast Ethernet that operates over UTP or fiber.

  • 1000 Mbps Ethernet—LAN specification known as Gigabit Ethernet that operates at 1000 Mbps over fiber. This technology is beyond the scope of this book.

Positioning Ethernet in the Campus

Given the variety of Ethernet speeds that can be deployed in the campus, you need to determine when, if, and where you want to upgrade to one or more of the Fast Ethernet implementations. Technology is currently in place to support the implementation of 10 Mbps or 100 Mbps Ethernet throughout the LAN, provided that you have the correct hardware and cabling infrastructure.

Where and what type of connectivity you use can be mapped back to the networking hierarchy of core, distribution, and access discussed in Chapter 1. Table 2-1 documents suggested Ethernet connectivity specifications according to the three-layer hierarchical model.

Table 2-1. Ethernet Connectivity Recommendations in a Hierarchical Network Model
 

Ethernet 10BaseT Position

Fast Ethernet Position

Access Layer

Provides connectivity between the end-user device and the access switch.

Gives high-performance PCs and workstations 100-Mbps access to the server.

Distribution Layer

Not typically used at this layer.

Provides connectivity between the access and distribution layers. Provides connectivity from the distribution layer to the core layer. Provides connectivity from the server block to the core layer.

Core Layer

Not typically used at this layer.

Provides inter-switch connectivity.

As noted in Table 2-1, 10 Mbps Ethernet is typically implemented at the access layer to connect to desktops, and faster technologies are used to interconnect network devices, such as routers and switches. However, many designers are considering the use of Gigabit Ethernet at the core, distribution, and access layers. Costs for cabling and adapters can make implementing Gigabit Ethernet at all three layers unappealing. Before making any decision, you must consider your networking needs and any future requirements you have that might potentially overwhelm a network running on slower media.

In general, Fast Ethernet technology can be used in a campus network in several different ways:

  • Fast Ethernet is used as the link between the access and distribution layer devices, supporting the aggregate traffic from each Ethernet segment on the access link.

  • Many client/server networks suffer from too many clients trying to access the same server, creating a bottleneck where the server attaches to the LAN. To enhance client/server performance across the campus network, enterprise servers are connected by Fast Ethernet links to ensure the avoidance of bottlenecks at the server. Fast Ethernet, in combination with switched Ethernet, creates an effective solution for avoiding slow networks.

  • Fast Ethernet links can also be used to provide the connection between the distribution layer and the core. Because the campus network model supports dual links between each distribution layer router and core switch, the combined traffic from multiple access switches can be load-balanced across these links.

Comparing Ethernet Media Requirements

In addition to considering network needs, before selecting an Ethernet implementation, you must consider the media and connector requirements for each implementation.

The cables and connector specifications used to support Ethernet are derived from the Electronic Industries Association and the newer Telecommunications Industry Association (EIA/TIA) standards body. The categories of cabling defined for Ethernet are derived from the EIA/TIA-568 (SP-2840) Commercial Building Telecommunications Wiring Standards. The EIA/TIA specifies a RJ-45 connector for unshielded twisted-pair (UTP) cable. The letters “RJ” stand for registered jack, and the number 45 refers to a specific wiring sequence.

Table 2-2 compares the cable and connector specifications for the most popular Ethernet implementations. The important difference to note is the media used for 10 Mbps Ethernet and 100 Mbps Ethernet. In today's networks, where you will see a mix of 10 Mbps and 100 Mbps needs, you must be aware of the need to change over to UTP category 5 to support Fast Ethernet.

Table 2-2. Ethernet Cabling and Connector Specifications
 

10Base5

10BaseT

100BaseTX

100BaseFX

Media

50-ohm coax (thick)

EIA/TIA Category 3, 4, 5 UTP, 2 pair

EIA/TIA Category 5 UTP, 2 pair

62.5/125 micron multimode fiber

Maximum Segment Length

500 meters

100 meters

100 meters

400 meters

Topology

Bus

Star

Star

Point-to-point

Connector

AUI

ISO 8877 (RJ-45)

ISO 8877 (RJ-45)

Duplex media interface connector (MIC) ST

As the acronym UTP implies, this cable consists of paired wires twisted together and wrapped in an unshielded outer jacket. These wires are unshielded because UTP derives all of its protection from the cancellation effect of the twisted pairs. The mutual cancellation effect of the wire twists minimizes the absorption of radiation of electrical energy from the surrounding environment. This helps reduce the problems in transmitting the signal, such as crosstalk (interference measured on a wire that is located near the wire sending the signal) and the effects of nearby electrical fields (noise).

Differentiating Between Connections

Figure 2-3 illustrates the different connection types used by each physical layer implementation. Of the three examples shown, the RJ-45 connector and jack are the most common.

Figure 2-3. Connector Types for Ethernet Cabling

UTP Implementation

If you look at an RJ-45 transparent end connector, you can see eight colored wires. These wires are twisted into four pairs within the outer jacket. Four of the wires are tip conductors (T1 through T4), and the other four are the ring conductors (R1 through R4). Tip and ring are terms that originated in the early days of the telephone. Today, these terms refer to the positive wire (tip) and the negative wire (ring) in the pair. The wires in the first port in a cable or connector are designated as T1 and R1, the second pair is T2 and R2, and so on. Table 2-3 and Table 2-4 detail two common UTP wiring standards.

Table 2-3. UTP EIA/TIA 568A Wiring Standard

Pin 1

Pair 2

White/Green

Tx + (Tip)

Pin 2

Pair 2

Green

Tx - (Ring)

Pin 3

Pair 3

White/Orange

Rx + (Tip)

Pin 4

Pair 1

Blue

Not used in 10BaseT or 100BaseT

Pin 5

Pair 1

White/Blue

Not used in 10BaseT or 100BaseT

Pin 6

Pair 3

Orange

Rx - (Ring)

Pin 7

Pair 4

White/Brown

Not used in 10BaseT or 100BaseT

Pin 8

Pair 4

Brown

Not used in 10BaseT or 100BaseT


Table 2-4. UTP EIA/TIA 568B Wiring Standard

Pin 1

Pair 2

White/Orange

Tx + (Tip)

Pin 2

Pair 2

Orange

Tx - (Ring)

Pin 3

Pair 3

White/Green

Rx + (Tip)

Pin 4

Pair 1

Blue

Not used in 10BaseT or 100BaseT

Pin 5

Pair 1

White/Blue

Not used in 10BaseT or 100BaseT

Pin 6

Pair 3

Green

Rx - (Ring)

Pin 7

Pair 4

White/Brown

Not used in 10BaseT or 100BaseT

Pin 8

Pair 4

Brown

Not used in 10BaseT or 100BaseT

An RJ-45 connector is the male component crimped on the end of the cable. As you look at the male connector from the front with the clip on the top, the pin locations are numbered 1 on the left down to 8 on the right, as shown in Figure 2-4.

Figure 2-4. RJ-45 Connector

The jack is the female component in a network device, wall or cubicle partition outlet, or patch panel. As you look at the device port, the corresponding female plug locations are 1 on the left and 8 on the right.

In order for electricity to run between the connector and the jack, the order of the wires must follow the EIA/TIA 568A and 568B standards, listed in Table 2-3 and Table 2-4. In addition to identifying the correct EIA/TIA category of cable to use for connecting a device, you will need to determine whether to use either a straight-through cable or a crossover cable.

Straight-Through Cable

A straight-through cable maintains the pin connection all the way through the cable. Thus, the wire connected to pin 1 is the same on both ends of the cable.

Figure 2-5 illustrates that the RJ-45 connectors on both ends show all of the wires in the same order. If you hold the two RJ-45 ends of a cable side by side in the same orientation, you'll see the colored wires (or strips or pins) at each connector end. If the order of the colored wires is the same at both ends, the cable is straight-through.

Figure 2-5. Straight-Through Cable Connections

Use a straight-through cable to connect devices such as PCs or routers to devices such as hubs or switches. Figure 2-6 shows the connection guidelines when using straight-through cable.

Figure 2-6. Determining When to Use Straight-Through Cable

Crossover Cable

A crossover cable crosses the critical pairs in order to properly align, transmit, and receive signals on devices with like connectors.

Figure 2-7 shows that the RJ-45 connectors on both ends have some of the wires on one side of the cable crossed to a different pin on the other side of the cable. Specifically for Ethernet, pin 1 on one side should be connected to pin 3 at the other end. Also, pin 2 on one end should be connected to pin 6 on the other end.

Figure 2-7. Crossover Cable Connections

A crossover cable is used for connecting similar devices—for example, switch to switch, switch to hub, hub to hub, router to router, or PC to PC. Figure 2-8 shows some guidelines for using crossover cables.

Figure 2-8. Determining When to Use Crossover Cable

Cabling the Campus

In order to cable the campus location, you must determine which physical media will be used and what type of connectors and cables you need to interface with your network devices.

Figure 2-9 illustrates how a variety of cable types may be required in a given network. The type of cabling required will be based on the type of Ethernet you choose to implement. In general, you must determine the physical media used—10 Mbps or 100 Mbps. This indicates what category of cable is required. Finally, locate the interface and determine if you need a crossover or straight-through cable.

Figure 2-9. Networks Might Require a Variety of Cable Types

TIP

Category 5 wiring is an ideal medium for cabling a building or campus, because it supports data rates of 10 Mbps as well as 100 Mbps. Should the need arise to migrate from one to the other, it would not be necessary to rewire the facility.

   

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