Table Of Contents

Troubleshooting

Understanding POST Results

Diagnosing Problems

Troubleshooting

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The LEDs on the front panel provide troubleshooting information about the switch. They show failures in the power-on self-test (POST), port-connectivity problems, and overall switch performance. For a full description of the switch LEDs, see the "LEDs" section on page 1-4.

You can also get statistics from the browser interface, from the command-line interface (CLI), or from a Simple Network Management Protocol (SNMP) workstation. Refer to the software configuration guide, the switch command reference guide on Cisco.com, or the documentation that came with your SNMP application for details.

This chapter describes these topics for troubleshooting problems:

•Understanding POST Results

•Diagnosing Problems

Understanding POST Results

As the switch powers on, it begins the POST, a series of tests that runs automatically to ensure that the switch functions properly. When the POST completes successfully, the System Status/ID LED is off, and the Console LED is solid green or amber. If the switch fails POST because of a misconfiguration or error, the System Status/ID LED blinks green, and the Console LED is off.

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Note POST failures are usually fatal. Call Cisco Systems if your switch does not pass POST.

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Diagnosing Problems

The LEDs on the front panel provide troubleshooting information about the switch. They show POST failures, port-connectivity problems, and overall switch performance. For a full description of the switch LEDs, see the "LEDs" section on page 1-4.

You can also get statistics from the browser interface, from the CLI, or from an SNMP workstation. Refer to the software configuration guide, the switch command reference guide on Cisco.com, or the documentation that came with your SNMP application for details.

You can access the Technical Support Website (http://www.cisco.com/tac) for a list of known hardware problems and extensive troubleshooting documentation including:

•Field notices

•Security advisories

•Troubleshooting resources

•Factory defaults

•Password recovery

•Recovery from corrupted or missing software

•Switch port problems

•Network interface cards

•Troubleshooting tools

Common switch problems fall into these categories:

•Poor performance

•No connectivity

•Corrupted software

Table 3-1 describes how to detect and resolve these problems.

Table 3-1 Common Problems and Their Solutions 

Symptom	Possible Cause	Resolution
Poor performance or excessive errors	Duplex autonegotiation mismatch.	Refer to the switch software configuration guide for information on identifying autonegotiation mismatches.
	Cabling distance exceeded •Port statistics show excessive frame check sequence (FCS), late-collision, or alignment errors.   •For 10/100/1000BASE-T connections: –The distance between the port and the attached device exceeds 328 feet (100 meters). –If the switch is attached to a repeater, the total distance between the two end stations exceeds the cabling guidelines. •For SFP port connections: –The distance between the SFP port and the attached device exceeds the SFP cabling guidelines.	•Refer to the switch software configuration guide for information on displaying port statistics. •Reduce the cable length to within the recommended distances. •Refer to your repeater documentation for cabling guidelines. •Refer to your SFP documentation for cabling guidelines.
	Bad adapter in attached device •Excessive errors found in port statistics. •STP checking for possible loops.	•Run adapter card diagnostic utility. •Wait 30 seconds for the port LED to turn green.
No connectivity	Incorrect or bad cable These are results of no link at both ends: •A crossover cable was used when a straight-through was required, or the reverse. •The cable is wired incorrectly. •A crossover or straight-through cable is wired incorrectly. •STP checking for possible loops.	•For the correct pinouts and the proper application of crossover or straight-through cables, see the "Two Twisted-Pair Cable Pinouts" section on page B-4. •Replace with a tested good cable. •For 1000BASE-T connections, be sure to use a twisted four-pair, Category 5 cable. •Wait 30 seconds for the port LED to turn green.
Unreadable characters on the management console	Incorrect baud rate.	Reset the emulation software to 9600 baud.
Amber system LED	Fatal POST error detected.	Contact Cisco Systems.
The switch port is placed in error-disabled state after SFP module is inserted	Bad or non-Cisco-approved SFP module.	Remove the SFP module from the switch, and replace it with a Cisco-approved module. Use the errdisable recovery cause gbic-invalid global configuration command to verify the port status, and enter a time interval to recover from the error-disable state. Refer to the switch command reference guide for information on the errdisable recovery command.
Switch does not recognize the SFP module	The SFP module might be installed upside down. The SFP module does not snap into the slot.	Verify that the SFP module is not installed upside down. Remove the SFP module. Inspect for physical damage to the connector, the module, and the module slot. Replace the SFP module with a known good SFP module.
The switch port is placed in error-disabled state after SFP is inserted	Bad or non-Cisco-approved SFP.	Remove the SFP module from the switch, and replace it with a Cisco-approved module. Use the errdisable recovery cause gbic-invalid global configuration command to verify the port status, and enter a time interval to recover from the error-disable state. Refer to the switch command reference guide for information on the errdisable recovery command.