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The HOSTS file uses a # (pound sign) to indicate a comment line, as does NetWare’s NCF files.

Don’t Overlook Physical Conditions

As we discussed in Chapter 6, you want to make sure that from a network design standpoint, the physical environment for a server is optimized for placement, temperature, and humidity. When troubleshooting an obscure network problem, don’t forget to check the physical conditions under which the network device is operating. Check for problems such as the following:

■    Excessive heat

■    Excessive humidity (condensation)

■    Low humidity (leads to ESD problems)

■    EMI/RFI problems

■    ESD problems

   Power problems

■    Unplugged cables

Don’t Overlook Cable Problems

Cables, generally speaking, work fine once they are installed properly. Rarely is the cabling system the problem, unless someone has made some change to it. If you suspect that the cabling system is the problem, try replacing the patch cables at the workstation and hub first. These are easiest to get to (and replace). If that solves the problem, you know the problem was related to the patch cable. It was either faulty or the wrong type.

If the patch cable isn’t the problem, use a cable tester (not a tone generator and locator) to find the source of the problem. Wires that are moved can be prone to breaking or shorting. A short can happen when the wire conductor comes in contact with another conductive surface, changing the path of the electrical signal. The signal will go someplace else instead of to the intended recipient. You can use cable testers to test for many types of problems, including:

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