Fault verification (Loopback messages)

A unicast Loopback Message is used for fault verification. To verify the connectivity between MEP and its peer MEP or a MIP, the Loopback Message is initiated by a MEP with a destination MAC address set to the MAC address of either a Maintenance association Intermediate Point (MIP) or the peer MEP. The receiving MIP or MEP responds to the Loopback Message with a Loopback Reply.

A Loopback message helps a MEP identify the precise fault location along a given MA. A Loopback message is issued by a MEP to a given MIP along an MA. The appropriate MIP in front of the fault will respond with a Loopback reply. The MIP behind the fault will not respond. For Loopback to work, the MEP must know the MAC address of the MIP to ping.