Troubleshooting guide

Troubleshooting SONET
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6. Check for a Path Remote Error Indication (P-REI) failure by viewing the Active
Defect field in the show controllers pos command output. A P-REI failure is
generated by the SONET device and sent out its transmit port when a failure is
detected on its receive port. A P-REI indicates a LOP failure condition, and
indicates high bit error rates coming from the transmitting (upstream) device.
Refer to the section Handling Data Loss on SONET Link for more information.
LOP Resolution
Follow these steps to resolve an LOP condition once you have isolated the cause or
problem area:
1. Check the fiber cabling for damage or improper use. For example, SONET cables
may be turned beyond their bending radius.
2. Ensure that both SONET terminal devices are operating at the same data rate. For
example, ensure that the SONET terminal devices are operating at either an OC3
or OC12 data rate.
3. Check for signal degradation.
4. Check fiber optic connectors for damage, and make sure they are clean.
Failed POS Module
A red fail LED indicates a POS module failure.
Perform one or more of the following tasks to try to re-enable the POS module:
1. Ensure that the POS module is firmly seated in the chassis.
2. Reinsert the POS module.
3. Replace the POS module.
4. Insert the POS module in another slot.
Fail LED Blinks and Lights Repeatedly
Follow these steps to resolve the POS module failure: