The loopback control PDU instructs the remote port to enter loopback mode.

Putting a port in loopback does not affect customer data flow

Both ports must rediscover the OAM capabilities of each other once the port is put back into service.

Both ports must still send Information PDUs to avoid going back to discovery mode.

When a port is in loopback mode, service mirroring will still work if it is a mirror-source or mirror-destination.

All packets, except for information PDUs, are looped back.