Cisco Systems CGS 2520 Switch Connections, Bad or Damaged Cable, Ethernet and Fiber-Optic Cables

Chapter 4 Troubleshooting

Diagnosing Problems

Switch Connections

•Bad or Damaged Cable, page 4-2

•Ethernet and Fiber-Optic Cables, page 4-2

•Link Status, page 4-2

•10/100 and 10/100/1000 Port Connections, page 4-3

•10/100 PoE+ Port Connections, page 4-3

•SFP Module, page 4-3

•Interface Settings, page 4-4

•Ping End Device, page 4-4

•Spanning Tree Loops, page 4-4

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).

•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.

Ethernet and Fiber-Optic Cables

Make sure that you have the correct 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 or 10/100/1000 Mb/s 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. See Table 2-1for recommended Ethernet cables.

Link Status

Verify that both sides have link. A broken wire or a shutdown port can cause one side to show link even though the other side does not have 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:

•Connect the cable from the switch to a known good device.

Cisco CGS 2520 Hardware Installation Guide

4-2 OL-31444-01