An apparatus and method for cable diagnostics is disclosed for deployment as part of an Ethernet communication system to conduct diagnostics. The system transmits one or more pulses which are Ethernet compatible and of finite duration. Reflections are detected and through processing and measurement of the amplitude and round-trip delay of the pulse's reflection, cable faults are located. In one embodiment, this innovation uses an IEEE 802.3 compliant transmit pulse, such as an auto-negotiation signal (AN pulse), to conduct cable diagnostics. The benefits of a standard compliant allow for use with any vendor on the far-end and the signal requires no special hardware or software to produce and, therefore, reduces system complexity and cost. To reduce incorrect measurements, the apparatus measures cable length and termination with multiple AN pulses. It then applies non-linear filters to redundant measurements in such a way that it produces accurate cable diagnostics information.