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Cisco Systems, Inc.
www.cisco.com
Troubleshooting
This chapter provides these topics for troubleshooting problems:
Diagnosing Problems, page 45
How to Recover Passwords, page 48
Finding the Switch Serial Number, page 48
Diagnosing Problems
The switch LEDs provide troubleshooting information about the switch. They show boot errors, port-connectivity
problems, and overall switch performance. You can also get statistics from Device Manager, the CLI, or an SNMP
workstation.
Switch Boot Fast
Note:
Contact your Cisco TAC representative if your switch does not successfully boot.
Note:
You can disable boot fast and run POST by using the Cisco IOS CLI.
Switch LEDs
Look at the port LEDs information when troubleshooting the switch. See
LEDs, page 5
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).
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 converters between the source and the destination. If possible,
bypass the patch panel, or eliminate media converters (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: