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v Verify that the device and the connected device are both powered on and
operating correctly.
v Verify that you have used the correct cable type for the connection:
– For twisted-pair connections to an end node, use straight-through cabling.
– For fiber optic connections, verify that the transmit port on the device is
connected to the receive port on the connected device, and that the receive
port on the device is connected to the transmit port on the connected device.
v Use the CLI to verify that the port has not been disabled through a
configuration change. If you have configured an IP address on the device, you
also can use the Web management interface or IronView Network Manager.
v If the other procedures don't resolve the problem, try using a different port or a
different cable.
Using Virtual Cable Testing to diagnose a cable
These devices support Virtual Cable Test (VCT) technology. VCT technology
enables you to diagnose a conductor (wire or cable) by sending a pulsed signal
into the conductor, then examining the reflection of that pulse. This method of
cable analysis is referred to as Time Domain Reflectometry (TDR). By examining
the reflection, the device can detect and report cable statistics such as local and
remote link pair, cable length, and link status.
Configuration notes
v This feature is supported on copper ports only. It is not supported on fiber ports.
v The port to which the cable is connected must be enabled when you issue the
command to diagnose the cable. If the port is disabled, the command is rejected.
v If the port is operating at 100 Mbps half-duplex, the TDR test on one pair will
fail.
v If the remote pair is set to forced 100 Mbps, any change in MDI or MDIX may
cause the device to interpret the Multilevel Threshold-3 (MLT-3) as a reflected
pulse, in which case, the device will report a faulty condition. In this case, it is
recommended that you run the TDR test a few times for accurate results.
Command syntax
To diagnose a cable using TDR, enter a command such as the following at the
Privileged EXEC level of the CLI.
FCX648SHPOE Switch# phy cable-diag tdr 1/1/1
This command diagnoses the cable attached to port 1/1/1.
Syntax: phy cable-diag tdr <port-num>
Viewing the results of the cable analysis
To display the results of the cable analysis, enter a command similar to the
following at the Privileged EXEC level of the CLI.
FCX648SHPOE Switch# show cable-diag tdr 1/1/1
Syntax: show cable-diag tdr <port-num>
Table 21 defines the fields shown in cable statistics.
Table 21. Cable statistics
This Line...
Port
Speed
Displays...
The port that was tested.
The current line speed of the port.
Chapter 3. Checking network devices and testing connectivity
41
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Troubleshooting
