Chapter 11
| Interface Commands
– 368 –
Command Usage
◆
Cable diagnostics are performed using Digital Signal Processing (DSP)
test method when the port link-up speed is 1 Gbps. DSP analyses the
cable by sending a pulsed signal into the cable, and then examining the
reflection of that pulse. If the port link-up speed is not 1 Gbps, then Time
Domain Reflectometry (TDR) test method is used. TDR also detects a
cable fault by sending a signal through the cable and reading the signal
that is reflected back. However, note that TDR can only determine if a link
is valid or faulty.
◆
This cable test is only accurate for Ethernet cables 7 - 100 meters long.
◆
The test takes approximately 5 seconds. Use the
command to display the results of the test, including common cable
failures, as well as the status and approximate length of each cable pair.
◆
Ports are linked down while running cable diagnostics.
◆
To ensure more accurate measurement of the length to a fault, first disable
power-saving mode (using the
command) on the link
partner before running cable diagnostics.
Example
Console#test cable-diagnostics interface ethernet 1/24
Console#
show
cable-diagnostics
This command shows the results of a cable diagnostics test.
Syntax
show cable-diagnostics dsp interface
[
interface
]
interface
ethernet
unit
/
port
unit
- Unit identifier. (Range: 1)
port
- Port number. (Range: 1-22/48)
Command Mode
Privileged Exec
Command Usage
◆
The results include common cable failures, as well as the status and
approximate distance to a fault, or the approximate cable length if no fault
is found.
◆
For link-down ports, the reported distance to a fault is accurate to /
- 2 meters. For link-up ports, the accuracy is +/- 10 meters.
