cmLoopType is a read-write enumeration selecting which kind of loopback test to run, such as looping at the DSL module port, the CPE Ethernet interface, or various WAN local/remote line points. An administrator picks the specific loop type that isolates the segment of the circuit under suspicion, for example a WAN remote-line loop to test the far end of a leased line. For example, to isolate whether a fault is on the local card or beyond it, an operator would first run scm-WAN-LocalLine(8) before trying scm-WAN-RemoteLine(9) to narrow down the fault location.