loop back testing can be done to check a leased line for faults.
A local loop would be either a software or hard loop on the NTU/Modem/Martis node in your premises.
Useful for checking your local cable and router interface.
A remote loop is the same except it is done on the NTU/Modem/Martis node at the remote end.
This verifies a path though the network into the remote site as far as the NTU/Modem/Martis node.
Looping can be done both ends if necessary to uncover any problems
to indicate if they are on the local / remote site or within the network.
I know why loopback used I want to know local loop back in leased line .
Is it Between CSU and Router or Between CSU and Telco ?
Is Remote loop back means CSU in one to CSU in other end ?
I just want to confirm ..
Local would be between the router and on site CSU/NTU.
Remote is via the telco network.
Depending on which part of the world your in the CSU/NTU is the demarc point of the Telco.