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The LEDs on the front panel provide troubleshooting information about the switch. They show failures in the POST, port-connectivity problems, and overall switch performance. For a full description of the switch LEDs, see the "System LED" section.
You can also get statistics from the browser interface, from the CLI, or from an SNMP workstation. See the Cisco IOS Desktop Switching Software Configuration Guide, the Cisco IOS Desktop Switching Command Reference (online only), or the documentation that came with your SNMP application for details.
This chapter describes the following topics for troubleshooting problems:
Table 3-1 lists the eight POST tests and their associated LEDs.
POST tests run automatically each time the switch is powered up. When the switch begins POST, the port status LEDs turn amber for 2 seconds, and then they turn green. The System LED flashes green, and the RPS LED turns off. As each test runs, the port status LEDs, starting with number 1, turn off. The port status LEDs for ports 2 to 8 each turn off in turn as the system completes a test.
When POST completes successfully, the port status LEDs return to the status mode display, indicating that the switch is operational. If a test fails, the port status LED associated with the test turns amber, and the system LED turns amber.
| Switch LED | Component Tested |
LED 1 | DRAM |
LED 2 | Flash memory |
LED 3 | Switch CPU |
LED 4 | System board |
LED 5 | CPU interface ASIC |
LED 6 | Switch core ASIC |
LED 7 | Ethernet controller ASIC |
LED 8 | Ethernet interfaces |
Common switch problems fall into the following categories:
Table 3-2 describes how to detect and resolve these problems.
| Symptom | Possible Cause | Resolution |
|---|---|---|
Poor performance or excessive errors.
| Autonegotiation mismatch.
Cabling distance exceeded. Port statistics show excessive frame check sequence (FCS), late-collision, or alignment errors. For 100BaseTX connections: | See the Cisco IOS Desktop Switching Software Configuration Guide for information on identifying autonegotiation mismatches. |
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| Reduce the cable length to within the recommended distances. |
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| See your 100BaseT repeater documentation for cabling guidelines. |
| For 10BaseT connections: The distance between the port and the attached device exceeds 100 meters. | Reduce the cable length to within the recommended distances. |
| Incorrect GigaStack cable connection. | Ensure that there is not a loopback in the stack configuration. |
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| Bad adapter in attached device. Excessive errors found in port statistics. |
Run adapter card diagnostic utility. |
| STP checking for possible loops. | Wait 30 seconds for LED to turn green. |
No connectivity. | Incorrect or bad cable. |
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| The following are indicated by no link at both ends: |
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| A crossover cable was used when a straight-through was required, or vice-versa. | For the correct pinouts and the proper application of crossover vs. straight-through cables, see the "Crossover and Straight-Through Cable Pinouts" section. |
| The cable is wired incorrectly. | Replace with a tested good cable. |
| STP checking for possible loops. | Wait 30 seconds for LED to turn green. |
System LED is amber, and all port LEDs are off. | Corrupted software. | Attach a monitor to the serial port to display the switch boot loader. For more information, see the Cisco IOS Desktop Switching Software Configuration Guide. |
Unreadable characters on the management console. | Incorrect baud rate. | Reset the emulation software to 9600 baud. |
Posted: Thu Apr 13 18:14:40 PDT 2000
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