Specifications

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Cisco MGX 8800/8900 Series Software Configuration Guide
Release 5.1, Part Number OL-6482-01, Rev. A0, January 25, 2005
Chapter 9 Switch Operating Procedures
Configuring a Line Loopback
• Far-end payload loopback- Loopback is similar to FarEnd loopback, except that the payload portion
of the data is re-transmitted. Framing is done by the Far end again.
• Remote line loopback - Loopback returns the remote data back to the far end. The received data
stream is looped back into the transmit path, overriding the data stream created internally by the
framer.
• Local loopback - Loopback allows the transmitted data to be looped back into the receiving path. It
can be used to test the internal hardware of the card.
Once your physical line is connected, you can perform a loopback test using the following procedure.
Step 1 Connect a single line to the appropriate transfer and receive ports on the backcard you want to test.
Step 2 Establish a configuration session with the active PXM1E, AXSM, or MPSM card using a user name with
SERVICE_GP privileges or higher.
Step 3 Enter the dsplns command to display the configuration for all lines on the current card.
Step 4 Enter the addlnloop <-line type> <bay.line> <-lpb loopback type> command.
addlnloop -ds3 2.1 -lpb 2
Step 5 Enter the dspln -<line type> <line_num> command to verify the that the appropriate line is in the
specified loopback state.
dspln -ds3 4.1
Note Before you can change the loopback type for an existing loopback, you must first delete the
loopback by executing dellnloop, or you can just enter the addlnloop command with the -lpb 1
(No loopback) option.
Configuring a Line Loopback on a Service Module
Once your physical line is connected, you can perform a loopback test using the following procedure.
Step 1 Connect a single line to the appropriate transfer and receive ports on the backcard you want to test.
Step 2 Establish a configuration session with the active PXM1E, AXSM, or MPSM using a user name with
SERVICE_GP privileges or higher.
Step 3 Enter the dsplns command to display the configuration for all lines on the current card.
Step 4 Enter the addlnloop <-line type> <bay.line> <-lpb loopback type> command.
addlnloop -ds3 2.1 -lpb 2
Step 5 Enter the dspln -<line type> <line_num> command to verify the that the appropriate line is in the
specified loopback state.
dspln -ds3 4.1
Before you can change the loopback type for an existing loopback, you must first delete the loopback by
executing dellnloop, or you can just enter the addlnloop command with the -lpb 1 (No loopback) option.