Description of the problem

Huawei OSN3500 devices are configured with four EGS4 single boards to interface with the digital communication CEs and carry 3G services. boards 5 and 6 are configured with BPS protection; boards 13 and 14 are configured with BPS protection, and boards 5 and 13 are used as the primary. On a certain day, the customer feedbacks that the main control board of the site reports HARD_BAD alarm, the alarm parameter is 0x0e 0xff 0xff 0xff 0xff 0xff 0xff 0xff, the alarm lasts for 2-3 hours and disappears automatically, and at the same time, there is a BPS status event reported. Business is not affected.

The site is using N4EGS4 single board multi-board ID configured for N3EGS4 single board usage. Host version is 5.21.18.50; EGS4 single board version is 1.14.

Alarm Information

Alarm name: HARD_BAD

Alarm parameter: 0x0e 0xff 0xff 0xff 0xff 0xff

Processing

1. On-site inspection of the pigtail connected to the CE revealed that the pigtail was faulty. After replacing the pigtail, the ETH-LOS alarm disappeared and the single-board link light was on. Continuous observation and then did not find HARD_BAD alarm reported.

2, the problem needs to be N4EGS4 single board software upgrade to 1.15 and above to completely solve the problem.

Root Cause

1, from the alarm parameters should be 14 board position EGS4 single board failure, but if it is a single board failure how will automatically disappear? On-site attempts to plug and unplug the single board, replace the single board after the failure remains. Rule out the single board failure factor.

2, because 13, 14 slots on the single board is a later expansion on the single board, so the expansion is suspected of motherboard pinback. Unplug the single board and carefully observed did not find the phenomenon of pinback.

3, on-site processing process found that the current network using the four EGS4 board only 14 slots in the single board reported ETH-LOS alarm, and the single board link light is not lit, so it is suspected that the single board with the port status abnormalities related to the port abnormalities can lead to the main control reported HARD_BAD alarms?

After the final localization:

Huawei SSN4EGS4 detects the port linkdown, it will periodically set the 8K line to the 2K state value, but every time before setting the 2K state, the software incorrectly set the low level (low level indicates a single-board failure), and maintained for 50ms, in this 50ms, the host happens to detect the hadbad state, it will report the hadbad alarm. In addition, as the 8K line state changes, the crossover board will report a BPS inverted state event as a result.

Therefore this alarm is a false alarm.

Recommendations and summary

After the discovery of the problem, more comparative analysis, to find out the faulty single board and the normal single board does not work, for difficult problems can be to the second line of experts and R & D for help.

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