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How to handle BUS_ERR alarm reported on cross-connect board

Publication Date:  2012-07-25 Views:  92 Downloads:  0
Issue Description
On an OptiX OSN 3500 NE of version on an unprotected chain, an SSN1SXCSA board is added. The standby cross-connect board housed in slot 10 reports the BUS_ERR and HSC_UNAVAIL alarms. 
Alarm Information
The standby SXCSA in slot 10 reports the following alarms:
1.Three BUS_ERR alarms, which contain the following parameters respectively:
   0x01 0x02 0x13 0x02 0xff
   0x02 0x02 0x13 0x02 0xff
   0x03 0x02 0x13 0x02 0xff
2.One HSC_UNAVAIL alarm with the following parameters
   0x04 0x01 0x09 0xff 0xff 
Handling Process
1. The BUS_ERR alarms indicate that the boards housed in slots 1, 2, and 3 report bus failures. The three boards are unlikely to all fail. The problem possibly lies outside the three boards.
2. Engineers doubt that the cross-connect board fails. Interchange the cross-connect boards in slots 9 and 10. The cross-connect board in slot 9 reports the preceding alarms. That is, the alarms are from the same hardware board. The problem possibly lies in the board. Replace the board with a new one. The fault, however, persists. The new board still reports the alarms.
3. Analyze the parameters of the BUS_ERR alarms. It is found that the fourth parameter is 0x02 in all the alarms. That is, the fault is detected during the handshake between the cross-connect boards. Therefore, the problem may lie in both cross-connect boards rather than in only the board that reports the alarms. Replace the cross-connect board that reports no alarms with a new one. The fault is rectified.
4. Therefore, the problem lies in the handshake mechanism of the cross-connect board which was previously considered normal. The problem drives the other cross-connect board wrong. As a result, the fault occurs. 
Root Cause
1. The cross-connect board fails.
2. The boards housed in slots 1, 2, and 3 fail.
3. The subrack fails. 
 Where there is a BUS_ERR alarm, there may be no problem. To locate such a fault, analyze the alarm parameters.