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Diagnosing Problems
Switch LEDs
Look at the port LEDs information when troubleshooting the switch. See the
for a description of the LED colors and their meanings.
Switch Connections
Bad or Damaged Cable
Always examine the cable for marginal damage or failure. A cable might be just good enough to connect
at the physical layer, but it could corrupt packets as a result of subtle damage to the wiring or connectors.
You can identify this problem because the port has many packet errors or it constantly flaps (loses and
regains link).
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Ethernet and Fiber-Optic Cables
Make sure that you have the correct cable:
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Link Status
Verify that both sides have a link. A broken wire or a shutdown port can cause one side to show a link
even though the other side does not have a link.
A port LED that is on does not guarantee that the cable is functional. It might have encountered physical
stress, causing it to function at a marginal level. If the port LED does not turn on:
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Cisco IE 4000 Switch Hardware Installation Guide
4-2
Exchange the copper or fiber-optic cable with a known good cable.
Look for broken or missing pins on cable connectors.
Rule out any bad patch panel connections or media convertors between the source and the
destination. If possible, bypass the patch panel, or eliminate media convertors
(fiber-optic-to-copper).
Try the cable in another port to see if the problem follows the cable.
For Ethernet, use Category 3 copper cable for 10 Mb/s UTP connections. Use either Category 5,
Category 5e, or Category 6 UTP for 10/100, 10/100/1000 Mb/s, and PoE connections.
Verify that you have the correct fiber-optic cable for the distance and port type. Make sure that the
connected device ports match and use the same type encoding, optical frequency, and fiber type.
Determine if a copper crossover cable was used when a straight-through was required or the reverse.
Enable auto-MDIX on the switch, or replace the cable.
Connect the cable from the switch to a known good device.
Make sure that both ends of the cable are connected to the correct ports.
Verify that both devices have power.
Verify that you are using the correct cable type. See
information.
Look for loose connections. Sometimes a cable appears to be seated but is not. Disconnect the cable,
and then reconnect it.
Chapter 4
"LEDs" section on page 1-9
Appendix C, "Cables and Adapters"
Troubleshooting
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