Troubleshooting Cpos Interfaces; Interface Physical Status Is Up, Link Protocol Status Is Down, And Loopback Is Detected - HP HSR6800 Configuration Manual

Verifying the configuration
Use the display interface serial 2/0/1/0:0 command to check connectivity and use the ping command
to check network reachability.

Troubleshooting CPOS interfaces

Interface physical status is UP, link protocol status is down, and
loopback is detected
Symptom
Connect the CPOS interface of a device to that of another vendor through SDH, bundle E1 channels on
the interface to form a serial interface and enable PPP encapsulation for it.
Use the display interface serial command to check information on interface status. It shows that the
physical state of the interface is UP, but the link protocol is DOWN; and loopback, though not configured,
is detected on some interfaces.
Solution
The fault is very likely caused if the multiplex unit configurations on the SDH transmission device
mismatch the E1 channel numbers on the CPOS interface on your device. This can result in timeslot
inconsistency at the two ends of transmission and also PPP negotiation failures and LCP anomalies.
Besides, if an idle timeslot on a loopback serial interface on the transmission device is used in
transmission, the information that loopback is detected is displayed. Use the debugging ppp lcp error
command to check loopback information.
Follow these steps to solve the problem:
1. Use the display controller cpos e1 command to view the multiplexing paths of the E1 channels or
calculate the multiplexing path as described in
numbers."
2. Check the configurations on the transmission devices against the calculating result in the last step
to make sure the same E1 multiplexing path is configured.
"Calculating E1/T1/E3/T3 channel sequence
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