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DGS-3120 Series Managed Switch CLI Reference Guide 
158 
 
•  When the link partner is powered down with errors, this command can detect whether 
the error is open, short, or crosstalk. In this case this command can also detect the 
distance of the error 
•  When there is no link partner with no errors and the link is up, this command can detect 
the cable length 
•  When there is no link partner with errors, this command can detect whether the error is 
open, short, or crosstalk. In this case this command can also detect the distance of the 
error 
 
When the link partner is Gigabit Ethernet ports: 
•  Where the link partner is powered on with no errors and the link is up, this command 
can detect the cable length 
•  Where the link partner is powered on with errors, this command can detect whether the 
error is open, short, or crosstalk. In this case this command can also detect the distance of 
the error 
•  Where the link partner is powered down with no errors and the link is down, this 
command cannot detect the cable length 
•  When the link partner is powered down with errors, this command can detect whether 
the error is open, short, or crosstalk. In this case this command can also detect the 
distance of the error 
•  When there is no link partner with no errors and the link is up, this command can 
detect the cable length 
•  When there is no link partner with errors, this command can detect whether the error is 
open, short, or crosstalk. In this case this command can also detect the distance of the 
error 
 
Note: This test is only for copper cable. The fiber port is not tested. For the combo ports, only the 
copper media will be tested. 
The cable diagnosis does not support on the Pair 1 and 4 if the link partner is FE port. 
If the link partner is FE port, the target port's link will be down after the test. 
 
Format 
cable_diag ports [<portlist> | all] 
 
Parameters