The priorities of the clock sources are set incorrectly, so the external clock source is unavailable after a fiber cut. After the priorities of the clock sources are re-set, the fault is rectified.
Symptom
The EOW board on NE A is connected to two clock sources from third-party equipment, the network clock tracing is normal, as shown in Figure 1. After a fiber cut occurs on the ring network, the external clock source becomes unvailable. In addition, NE D reports the LTI alarm, and a large amount of bit errors occur.
Cause Analysis
In normal cases, the working path of the clock tracing is external clock source->NE A->NE B->NE C->NE D->NE F; the protection path is external clock source->NE A->NE F->NE D->NE C->NE B. After a fiber cut occurs on the ring network, the clock source of NE D is lost. After the clock configuration of the network is checked, it is found that System Clock Source Priority Table on NE D is not configured.
Procedure
- Query the clock subnet configuration by using the NMS.
- In the NE Explorer of NE D, choose .
- Choose the Clock Quality tab, and Choose the Clock Source Quality. Click Query. The return shows that the system receives the G.811 primary reference clock (PRC) from the 11-SL64 board.
- Choose to obtain the clock tracing relationship of NE D. The west clock source (on NE C) next to NE D is unavailable, so NE C should trace its east clock source.
- In the NE Explorer of NE D, choose . Then, select Priority Table for Phase-Locked Sources of 2nd External Clock Output, and click Create to add 8-SL64 and 11-SL64 as clock sources.
- In the Clock View, refresh the clock tracing relationship. Then, the alarm clears.
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