A method for determining whether a physical layer device under test is defective may include establishing a closed communication path between a verified physical layer device and the physical layer device under test via an optical interface of the verified physical layer device and an optical interface of the physical layer device under test. Alternately, the electrical interface may also be used for testing. A packet generator may transmit test packets over the established closed communication path and at least a portion of the test packets from the physical layer device under test may be received by the verified physical layer device. Subsequently, the verified physical layer device may compare at least a portion of the received test packets with at least a portion of the generated test packets in order to determine whether the physical layer device is defective or operational.