Dear Somnath, [Pls Rate if HELPS]

The following are the steps required to perform loopback testing: (Answers for your Question) :

Step 1 Put the remote CSU or DSU into remote loopback mode

Step 2 Using the show interfaces serial exec command, determine whether the line protocol remains up with the status line indicating "Serial x is up, line protocol is up (looped)," or if it goes down with the status line indicating "line protocol is down."

Step 3 If the line protocol remains up (looped), the problem is probably at the remote end of the serial connection (between the remote CSU/DSU and the remote router). Perform both local and remote tests at the remote end to isolate the problem source.

Step 4 If the line status changes to "line protocol is down" when remote loopback mode is activated, make certain that ones density is being properly maintained. The CSU/DSU must be configured to use the same framing and coding schemes used by the leased-line or other carrier service (for

example, ESF and B8ZS).

Step 5 If problems persist, contact your WAN

service organization

PLS RATE if HELPS

Best Regards,

Guru Prasad R