When operators see a connectivity fault message from CCM in the system log, they can send a loopback message (LBM) or a link trace message (LTM).
These are also referred to as a Layer 2 ping or a traceroute message. You can send with an LBM or an LTM only from an MEP (either UP or DOWN).
You can only send a ping from a MEP, and you ping to the unique system MAC address on the switch you are testing connectivity to. The operator sends out a unicast LBM, and the first MIP or MEP on the switch with the destination MAC address matching the embedded MAC address replies with an LBR (loopback reply).
You can only send a traceroute (LTM) from a MEP. You send the traceroute to the unique system MAC address on the switch to which you are testing connectivity. The system sends out an LTM to the special multicast address. If the destination address is not present in the FDB (forwarding database), the LTM is flooded on all the ports in the MIP node. Each MIP in the path passes the frame only in the direction of the path and sends a link trace reply (LTR) message back to the originating with information that the LTM passed. The traceroute command displays every MIP along the path (see traceroute mac port).
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