Testing a Cable

Updated on 23 Jan 2024
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You can test the quality of copper cables, connectors and terminations attached to each unit. For this, the unit uses Time-Domain Reflectometry (TDR). You can quickly find opens, shorts, cable impedance mismatches, bad connectors and termination mismatches. If no problem in the cable is found, this test reports the cable length. If a problem is found, the test reports the distance at which the problem is detected.

Note: You can only test cables in use on RJ45 ports. SFPs (optical or electrical) are not supported.

To test the quality of a cable and view results

Access the page Port ▶ Cable.
A summary of all cable test results for all available copper ports is displayed. For more information on specific parameters, refer to the following table.
Click the Connector to test a cable.
Click the Perform test button to start the test.

The test should last only a few seconds and the status of each channel is updated as the tests are run.

Cable Verification (Port ▶ Cable)

Parameter	Description
Connector	The physical connector the port is using
Channel A Channel B Channel C Channel D	The results for each pair in a four-pair cable are presented in these four columns.
Status	The current status of the cable: GOOD: Normal cable SHORT: The positive and negative lines of the same pair are touching. The possible causes are: Line of the RJ-45 cable may be touching the wire closet patch panel. Line of the RJ-45 cable may be worn from constant use and positive and negative lines may be touching. OPEN: There is a cut on a pair. The possible causes are: Line of the RJ-45 cable may be left unconnected at the wiring closet patch panel. Line of the RJ-45 cable may have been cut unintentionally. The other end of the RJ-45 cable may be simply unconnected. FORCED: A persistent noise in the channel. This can be caused by a link partner running in forced 10/100 Mbps. Cable length is not available in the FORCED state. FAIL: The test failed. The link partner must lose the link in order to start the test. If the PHY receives a continuous signal during 125 ms, it reports the test result as FAIL. Impedance Mismatch Status: Whenever the effective impedance is not 100 Ohms. The possible causes are: Different quality cables are connecting through a cable extender. A cable with the wrong quality is being used.
Length	If no problem in the cable is found, this test reports the cable length. If a problem in the cable is found, this test gives the approximate distance at which the problem is detected.

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