Networking / Beginners

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Where the Cable Is Used

Imagine that you have been called in to track down a problem with a network. After some time, you discover that clients connect to the network via standard UTP cable run down an elevator shaft. UTP has poor resistance to electromagnetic interference (EMI), and therefore UTP and the electrical equipment associated with elevators react to each other like oil and water. The same can be said of cables that run close to fluorescent light fittings. Such problems might seem far-fetched, but you would be surprised at how many environments you will work in that have random or erratic problems that users have lived with for a long time and nothing has been done.

NOTE: In many buildings, risers are used for running cables between floors. A riser is a column that runs from the bottom of the building to the top. Risers are used for running all kinds of cables, including electrical and network cables.

Part of troubleshooting wiring problems is to identify where the cable is run to isolate whether the problem is a result of crosstalk or EMI. Be aware of problems associated with interference and the distance limitations of the cable used.

TIP: Never assume that the cable you use is good until you test it and confirm that it is good. Sometimes cables break, and bad media can cause network problems.

If you find a problem with a network's cable, you can do various things to correct it. For cables that exceed the maximum distance, you can use a repeater to regenerate the signal, try to reroute the cable over a more economical route, or even replace the type of cable with one that has greater resistance to attenuation. The method you choose often depends on the network's design and your budget.

For cable affected by EMI or other interference, consider replacing the cable with one that is more resistant to such interference or rerouting the cable away from the source of the interference. If you do reroute cable, pay attention to the maximum distance, and make sure that as you cure one problem you don't create another.

Wiring Issues

Depending on where the cable is used and the type of cable, you might encounter some specific cable-related problems. This section describes some problems you might encounter and their solutions.