This read-write object specifies the type of loopback to be established for the test: farEndLoopback loops traffic back at the remote end, facilityLoopback loops it back at a local facility point, and metallicLoopback loops it back at the physical copper pair. Each type isolates a different segment of the circuit for testing. An admin trying to determine whether a fault lies in the local wiring versus the far-end equipment would compare results between metallicLoopback and farEndLoopback tests.