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9.2 | |
Network Testing | |
| 9.2.4 | |
Layer 1 troubleshooting using indicators |
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Indicator lights are a useful tool for
troubleshooting. Most interfaces or NICs will have indicator lights
that show whether there is a valid connection. Often this light is
called the link light. The interface may also have lights to indicate
whether traffic is being transmitted (TX) or received (RX). If the
interface has indicator lights that do not show a valid connection,
power off the device and reseat the interface card. A faulty or
incorrect cable could also cause a link light to indicate a bad
connection or no link. Check to make sure that all cables are connected to the appropriate ports. Make sure that all cross-connects are properly patched to the correct location using the appropriate cable and method. Verify that all switch or hub ports are in the correct VLAN or collision domain, and have appropriate options set for spanning tree and other considerations. Verify that the proper cable is being used. A crossover cable may be required for direct connections between two switches or hubs, or between two hosts such as PCs or routers. Verify that the cable from the source interface is properly connected and is in good condition. If there is doubt that the connection is good, reseat the cable and ensure that the connection is secure. Try replacing the cable with a known working cable. If this cable connects to a wall jack, use a cable tester to ensure that the jack is properly wired. Also check any transceiver in use to ensure that it is the correct type, is properly connected, and is properly configured. If replacing the cable does not resolve the problem, try replacing the transceiver if one is being used. Always check to make sure that the
device is powered on. Always check the basics before running
diagnostics or attempting complex troubleshooting.
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