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Cisco Catalyst Switch Module 3110 and 3012 for IBM BladeCenter Software Configuration Guide
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Chapter 47 Troubleshooting
Using TDR
Using TDR
These sections contain this information:
• Understanding TDR, page 47-15
• Running TDR and Displaying the Results, page 47-15
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 10-Gigabit Ethernet
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
When you run TDR, the switch reports accurate information if
• The cable for the Gigabit link is a solid-core cable.
• The open-ended cable is not terminated.
When you run TDR, the switch does not report accurate information if
• The cable for the Gigabit link is a twisted-pair cable or is in series with a solid-core cable.
• The link is a 10-Megabit or a 100-Megabit link.
• The cable is a stranded cable.
• The link partner is a Cisco IP Phone.
• The link partner is not IEEE 802.3 compliant.
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.
