Cisco Systems 3750E manual Using TDR, Understanding TDR, 45-20

Chapter 45 Troubleshooting

Using TDR

Table 45-2	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.

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 45-20

•Running TDR and Displaying the Results, page 45-21

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 and 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

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
45-20	OL-9775-02