The run diagnostics cable ports command enables cable diagnostics on copper ports using Time Domain Reflectometry (TDR) technology embedded in the PHY chips. This diagnostic tool helps identify physical issues such as cable breaks, shorts, or interference on individual twisted pairs.
Note
Running cable diagnostics may momentarily interfere with traffic on active ports.Cable diagnostics are supported only on copper ports. The command is not supported on:
| State | Meaning |
|---|---|
| Ok | No fault detected; pair is functioning normally. |
| Open | Pair is not terminated or has a physical break. May be expected if unplugged. |
| Short | Conductors are shorted together. |
| Crosstalk | Interference detected between pairs; may indicate poor shielding or cable quality. |
| Unknown | Diagnostic failed or result is inconclusive. |
Note
An Open state may be expected if the cable is not connected at the far end. If the cable is expected to be connected, this may indicate a fault.The following example runs diagnostics on port 14:
# run diagnostics cable ports 14
Do you want to continue cable diagnostics? (y/N) Yes
cablediag: 1.1.0.14
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ C A U T I O N +
+ cablediag will momentarily interfere with traffic on active ports +
+-----------------------------------------------------------------------+
+ Ports: 14 +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Collecting port cable diagnostic information may take a moment...
port 14: cable (4 pairs, length +/- 10 meters)
pair A Ok, length 0 meters
pair B Ok, length 0 meters
pair C Ok, length 4 meters
pair D Ok, length 4 meters
Example with Faults
port 3: cable (4 pairs, length +/- 10 meters) pair A Ok, length 5 meters pair B Open, length 7 meters pair C Crosstalk, length 6 meters pair D Ok, length 5 meters