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This chapter provides these topics for troubleshooting problems:
The LEDs on the front panel provide troubleshooting information about the switch. They show power-on self-test (POST) failures, port-connectivity problems, and overall switch performance. You can also get statistics from the browser interface, the command-line interface (CLI), the Cisco Intelligence
Engine 2100 (IE2100) Series Configuration Registrar, or a Simple Network Management Protocol (SNMP) workstation. See the switch software configuration guide, the switch command reference, or the documentation that came with your IE2100 or SNMP application for details.
As the switch powers on, it begins the POST, a series of tests that runs automatically to ensure that the switch functions properly. It might take several minutes for the switch to complete POST.
POST starts with LED tests that cycles once through the System, Alarm, Setup, Pwr A, and Pwr B LEDs. While POST proceeds, the System LED blinks green, and all the other LEDs remain off. If POST completes successfully, the System LED changes to solid green, and the other LEDs display their normal operating status. If the switch fails POST, the System LED turns red.
Note POST failures are usually fatal. Contact your Cisco technical support representative if your switch does not pass POST.
If you have a terminal connected to the console port, you can also view POST status and test results on the terminal. If the terminal displays garbled characters, you might need to reset the terminal-emulation software to 9600 bits per second. For more information about viewing results on a terminal, see the “Verify POST Results” section.
Warning If you connect or disconnect the console cable with power applied to the switch or any device on the network, an electrical arc can occur. This could cause an explosion in hazardous location installations. Be sure that power is removed or the area is nonhazardous before proceeding.
To verify switch operation, perform POST on the switch in a nonhazardous location before installation. Statement 1065
If you have physical access to the switch, look at the port LEDs for information about the switch. See the “LEDs” section for a description of the LED colors and their meanings.
Review this section when troubleshooting switch connection problems.
Always make sure that the cable does not have marginal damage or failure. A cable might be connect at the physical layer, but it could corrupt packets as a result of subtle damage to the wiring or connectors. If the port has many packet errors or the port constantly flaps (loses and regains link):
Make sure that you have the correct cable type for the connection:
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 cable for the distance and the port type. Make sure that the connected device ports both match and use the same type encoding, optical frequency, and fiber type. For more information about cabling, see the “Cable and Adapter Specifications” section.
Determine if a crossover cable was used when a straight-through was required or the reverse. Enable auto-MDIX on the switch, or replace the cable. See the “Cable and Adapter Specifications” section for recommended Ethernet cables.
Verify that both sides have link. A single broken wire or one shutdown port can cause one side to show link, but the other side does not have link.
A link LED does not guarantee that the cable is fully functional. The cable might have encountered physical stress that causes it to function at a marginal level. If the link light for the port does not come on:
Use only Cisco SFP modules on the switch. Each Cisco module has an internal serial EEPROM that is encoded with security information. This encoding provides a way for Cisco to identify and validate that the module meets the requirements for the switch. Check these items:
A cause of port connectivity failure can be a disabled port. Verify that the port or interface is not disabled or powered down for some reason. If a port or interface is manually shut down on one side of the link or the other side, the link does not come up until you re-enable the port. Use the show interfaces privileged EXEC command to verify the port or interface error-disabled, disabled, or shutdown status on both sides of the connection. If needed, re-enable the port or the interface.
Test the end device by pinging from the directly connected switch first, and then work your way back port by port, interface by interface, trunk by trunk, until you find the source of the connectivity issue. Make sure that each switch can see the end device MAC address in its content-addressable memory (CAM) table.
Spanning Tree Protocol (STP) loops can cause serious performance issues that look like port or interface problems. In this situation, the switch bandwidth is used over and over again by the same frames, leaving little room for legitimate traffic.
Loops can be caused by a unidirectional link. A unidirectional link occurs whenever the traffic sent by the switch is received by its neighbor, but the traffic from the neighbor is not received by the switch. A broken fiber-optic cable, other cabling, or a port issue could cause this one-way communication.
You can enable UniDirectional Link Detection (UDLD) on the switch to help identify difficult-to-find unidirectional link problems. UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD detects unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and due to misconnected interfaces on fiber-optic links. For information about enabling UDLD on the switch, see the “Understanding UDLD” section in the “Configuring UDLD” chapter of the software configuration guide for this release.
Review this section when troubleshooting switch performance problems.
If the port statistics show a large amount of alignment errors, frame check sequence (FCS), or late-collisions errors, this might indicate a speed or duplex mismatch.
A common issue with speed and duplex is when the duplex settings are mismatched between two switches, between a switch and a router, or between the switch and a workstation or server. This can happen when manually setting the speed and duplex or from autonegotiation issues between the two devices. A mismatch occurs under these circumstances:
To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex and speed:
Problems sometimes occur between the switch and third-party network interface cards (NICs). By default, the switch ports and interfaces are set to autonegotiate. It is common for devices like laptops or other devices to be set to autonegotiate as well, yet sometimes autonegotation issues occur.
To troubleshoot autonegotiation problems, try manually setting both sides of the connection. If this does not solve the problem, there could be a problem with the firmware or software on your NIC. You can resolve this by upgrading the NIC driver to the latest version available from the manufacture.
If the port statistics show excessive FCS, late-collision, or alignment errors, verify that the cable distance from the switch to the connected device meets the recommended guidelines. See the “Cable and Connectors” section for cabling guidelines.
Follow these steps to return your switch to the factory default settings. These are reasons why you might want to reset the switch:
To reset the password on the switch:
2. Power on the switch, and at the same time, press and hold down the Express Setup button until all the system LEDs turn red.
3. Release the Express Setup button, and the switch continues to boot.
After the switch restarts, continue to run Express Setup.
The switch now behaves like an unconfigured switch. You can configure the switch by using Express Setup as described in the getting started guide that is included with the switch. You can also configure the switch by using the CLI setup procedure described in Appendix D, “Configuring the Switch with the CLI-Based Setup Program.”
Password recovery is a feature that a system administrator can enable or disable. If password recovery is disabled, the only way to recover from a lost or forgotten password is to clear the switch configuration entirely. For this procedure, see the “How to Clear the Switch IP Address and Configuration” section.
The switch software configuration guide provides details about enabling and disabling the password recovery feature and the procedure for recovering passwords.
If you contact Cisco Technical Assistance, you need to know the serial number of your switch. See Figure 3-1 and Figure 3-2 to find the serial number on your switch or module. See Figure 3-3 to find the serial number on your power converter. You can also use the show version privileged EXEC command to get the switch serial number.
Figure 3-1 Serial Number Location for the Cisco IE-3000-4TC and the Cisco IE-3000-8TC Switch
Figure 3-2 Serial Number Location for the Cisco IEM-3000-8TM and the Cisco IEM-3000-8FM Module
Figure 3-3 Serial Number Location for the Cisco PWR-IE3000-AC Power Converter