Using Tdr - Cisco Catalyst 2975 Software Configuration Manual

Chapter 38 Troubleshooting

Using TDR

These sections contain this information:
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Understanding TDR
You can use the Time Domain Reflector (TDR) feature to diagnose and resolve cabling problems. When
running TDR, a local device sends a signal through a cable and compares the reflected signal to the initial
signal.
TDR is supported only on 10/100/1000 copper Ethernet ports. It is not supported on SFP module ports.
TDR can detect these cabling problems:
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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:
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Running TDR and Displaying the Results
When you run TDR on an interface, you can run it on the stack master or a stack member.
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.
Using Debug Commands
These sections explains how you use debug commands to diagnose and resolve internetworking
problems:
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OL-19720-02
Understanding TDR, page 38-19
Running TDR and Displaying the Results, page 38-19
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.
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
Enabling Debugging on a Specific Feature, page 38-20
Enabling All-System Diagnostics, page 38-20
Redirecting Debug and Error Message Output, page 38-21
Catalyst 2975 Switch Software Configuration Guide
Using TDR
38-19