The Time-Domain Reflectometer (TDR) feature helps characterize and locate cable faults in the twisted wire pairs. TDR involves showing a reflection at any impedance change within the cable when a low voltage pulse is sent into the cable. TDR measures the time between release and return of the low voltage pulse from any reflections. The distance to the reflection can be calculated by measuring the time and the transmission velocity of the pulse.

TDR or Cable Diagnostics is a port feature supported on some switches running ArubaOS-CX software. TDR is used to detect cable faults on 1GbT, 2.5G-SmartRate, 5G-SmartRate, and 10G-SmartRate (only applicable for 6400 switch) ports.

How TDR works on ArubaOS-CX platforms

The implementation of TDR in ArubaOS-CX platforms is dependent on the physical layer chips (PHYs) that are part of the front-end network ports hardware. ArubaOS-CX switches activate TDR on the PHY when a user enters the diag cable-diagnostic command. The switch waits for the report about TDR measurements from the PHY. The switch then reads the results and reports the values to the user.