Using Network Tools


There are a number of tools a network administrator might be required to use. Some of these tools (such as the tone generator and locator) can be used for troubleshooting media connections, and others (such as wire crimpers and punchdown tools) are used to create network cables and connections. In either case, for the Network+ exam, you will be expected to identify the function of various networking tools.

Wire Crimpers

Wire crimpers are tools that most network administrators will find themselves using at some point. Basically, a wire crimper is a tool that you use to attach media connectors to the ends of cables. For instance, you use one type of wire crimper to attach RJ-45 connectors on Unshielded Twisted Pair (UTP) cable, and you use a different type of wire crimper to attach Bayonet Neill Concelman (BNCs) to coaxial cabling.

In a sense, you can think of a wire crimper as a pair of special pliers. You insert the cable and connector separately into the crimper, making sure that the wires in the cable align with the appropriate connectors. Then, by squeezing the crimper's handles, you force metal connectors through the wires of the cable, making the connection between the wire and the connector.

If you do need to make your own cables instead of buying them, it is a good idea to test them before putting them on the network. It only takes a momentary lapse to make a mistake when creating a cable, and you can waste time later trying to isolate a problem in a faulty cable. If you do choose to make your own cables, you should test them with an electronic 'patch tester' before installing them on your network.

Punchdown Tools

If you have ever looked in a network closet, you have probably seen a distribution block, more commonly called a patch panel. A patch panel is a freestanding or wall-mounted unit with a number of port connections on the front. In a way, it looks like a wall-mounted hub without the light-emitting diodes (LEDs). The patch panel provides a connection point between network equipment such as hubs and switches and the ports to which PCs are connected, which are normally distributed throughout a building.

Behind each of the individual RJ-45 jacks on the patch panel are connectors to which are attached the eight wires from a piece of twisted-pair cable. These wires are commonly attached to the patch panel by using a tool called a punchdown tool. To use the punchdown tool, you place the wires from the cable into the appropriate slots in the back of the patch panel, and then use the tool push the wires firmly down into the slots. The insulation is stripped, and the wire becomes firmly embedded into the connector. Because the connector strips the insulation on the wire, it is known rather grandiosely as an insulation displacement connector (IDC).

Tone Generators (and Tone Locators)

A tone generator is a device that can save a network installer many hours of frustration. Strangely, the tone generator has a partner that goes wherever it goes but is seldom mentioned: the tone locator. You might hear the tone generator and the tone locator referred to as the fox and hound.

As you might expect, the purpose of the tone generator is to generate a signal that is transmitted on the wire you are attempting to locate. At the other end, you press the tone locator against individual wires. When it makes contact with the wire that has the signal on it, the locator emits an audible signal or tone.

The tone locator is a useful device, but it does have some drawbacks. First, it often takes two people to operateone at each end of the cable. Of course, one person could just keep running back and forth; but if the cable is run over great distances, this could be a problem. Second, using the tone generator is a time-consuming process because it must be attached to each cable independently.

Media Testers

A media tester, also called a cable tester, is used to test whether a cable is working properly. Any tool that facilitates the testing of a cable can be deemed a cable tester. One of the simplest cable-testing devices is a multimeter. By using the continuity setting, you can test for shorts in a length of coaxial cable; or, if you know the correct cable pinouts and have needlepoint probes, you can test twisted-pair cable. Various other single-purpose and multipurpose devices allow you to test cables. Some of these devices tell you if the cable is working correctly and, if it's not, give you some idea why it's not.

Because the majority of network cabling is copper based, most of the tools designed to test cabling are designed for copper-based cabling. However, when you test fiber-optic cable, you need an optical tester.

An >optical cable tester performs the same basic function as a wire media tester, but on optical media. Unlike wire cables, the most common problem with an optical cable is a break in the cable that prevents the signal from reaching the other end. Because of the extended distances that can be covered with fiber-optic cables, degradation is rarely an issue in a fiber-optic LAN environment.

Ascertaining whether a signal reaches the other end of a fiber-optic cable is a relatively easy task, but when you determine that there is a break, the problem becomes locating the break. That's when you need a tool called an optical time-domain reflectometer (OTDR). By using an OTDR, you can locate how far along in the cable the break occurs. The connection on the other end of the cable might be the source of the problem, or perhaps there is a break halfway along the cable. Either way, an OTDR can pinpoint the problem.

Unless you work extensively with fiber-optic cable, you're unlikely to have an OTDR or even a fiber-optic cable tester in your toolbox. Specialized cabling contractors will have them, though, so knowing that they exist is important.

Hardware Loopback Connectors

Hardware loopback connectors are simple devices that redirect outgoing transmissions from a system directly back into it. Hardware loopback connectors are used in conjunction with diagnostic software for diagnosing transmission problems. Loopback connectors are available for a number of ports, including RJ-45, serial, and parallel ports.

Specifically, a hardware loopback connector loops the outgoing data signal wires back into the system on the incoming data signal line. In effect, it tricks the system into thinking that the PC is sending and receiving data on the network, when in fact the data being sent is just being rerouted back in. Note that in some cases, a hardware loopback connector is referred to as an adapter or a plug.

The hardware loopback adapter checks the electrical signals sent out from the NIC.




    Network+ Exam Cram 2
    Network+ Exam Cram 2
    ISBN: 078974905X
    EAN: N/A
    Year: 2003
    Pages: 194

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