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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 42 Troubleshooting Using Debug Commands
Note Only the Cisco ME 3400-12CS and ME 3400-2CS switches have dual-purpose ports.
TDR can detect these cabling problems:
• Open, broken, or cut twisted-pair wires—The wires are not connected to the wires from the remote
device.
• Shorted twisted-pair wires—The wires are touching each other or the wires from the remote device.
For example, a shorted twisted pair can occur if one wire of the twisted pair is soldered to the other
wire.
If one of the twisted-pair wires is open, TDR can find the length at which the wire is open.
Use TDR to diagnose and resolve cabling problems in these situations:
• Replacing a switch
• Setting up a wiring closet
• Troubleshooting a connection between two devices when a link cannot be established or when it is
not operating properly

Running TDR and Displaying the Results

To run TDR, enter the test cable-diagnostics tdr interface interface-id privileged EXEC command:
To display the results, enter the show cable-diagnostics tdr interface interface-id privileged EXEC
command. For a description of the fields in the display, see the command reference for this release.
Note TDR is supported only on the copper Ethernet 10/100 ports or on dual-purpose ports configured as
10/100/100 ports by using the RJ-45 connector.
Using Debug Commands
These sections explains how you use debug commands to diagnose and resolve internetworking
problems:
• Enabling Debugging on a Specific Feature, page 42-18
• Enabling All-System Diagnostics, page 42-18
• Redirecting Debug and Error Message Output, page 42-18
Caution Because debugging output is assigned high priority in the CPU process, it can render the system
unusable. For this reason, use debug commands only to troubleshoot specific problems or during
troubleshooting sessions with Cisco technical support staff. It is best to use debug commands during
periods of lower network traffic and fewer users. Debugging during these periods decreases the
likelihood that increased debug command processing overhead will affect system use.
Note For complete syntax and usage information for specific debug commands, see the command reference
for this release.