49-19
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter49 Troubleshooting
Using TDR
To end a trace in progress, enter the escape sequence (Ctrl-^ X by default). Simultaneously press and
release the Ctrl, Shift, and 6 keys and then press the X key.
Using TDR
These sections contain this information:
Understanding TDR, page 49-19
Running TDR and Displaying the Results, page49-20

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 10/100/100 copper Ethernet ports. It is not supported on 10/100 ports,
10-Gigabit module ports, or on SFP module 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
Table49-2 Traceroute Output Display Characters
Character Description
* The probe timed out.
? Unknown packet type.
A Administratively unreachable. Usually, this output means that an access list is
blocking traffic.
H Host unreachable.
N Network unreachable.
P Protocol unreachable.
Q Source quench.
U Port unreachable.