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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The TU_LOP_VC12 is an alarm indicating the loss of pointer in the TU of the VC-12 lower order path. If a board has detected that the TU-PTR value is an invalid pointer or NDF reversion in eight consecutive frames, the TU_LOP_VC12 alarm is reported.


Alarm Severity Alarm Type


Communication alarm


When you view an alarm on the network management system, select the alarm. In the Alarm Details field display the related parameters of the alarm. The alarm parameters are in the following format: Alarm Parameters (hex): parameter1 parameter2...parameterN. For details about each parameter, refer to the following table.

Name Meaning

Parameter 1

Indicates the optical interface number. The value is always 0x01.

Parameter 2, parameter 3

Indicates the VC-12 path number that generates the alarm.

Impact on the System

When the TU_LOP_VC12 alarm occurs, the TU pointer in the signals received by the board on the cross-connection side is lost. As a result, the services in the path are unavailable. If the SNCP protection is configured for the board in the lower order path, the TU_LOP_VC12 will trigger the switching of the SNCP protection.

When the TU_LOP_VC12 alarm occurs, the system returns the LP_RDI alarm to the opposite station.

Possible Causes

The possible causes of the TU_LOP_VC12 alarm are as follows:

  • The higher order alarms occur.
  • The relevant path at the opposite station is faulty.
  • The services are incorrectly configured.
  • Cross-connect unit fault.


  1. View alarms on the NMS to check whether the R_LOS alarm is reported on the upstream NE. If the R_LOS alarm is reported on the upstream NE, handle the alarm by following instructions in R_LOS. If the R_LOS alarm is not reported on the upstream NE, go to 2.
  2. Check whether the T_ALOS, E1_LOS, or UP_E1_AIS alarm is reported on the peer NE. If these alarms exist, handle these alarms by following instructions in T_ALOS, E1_LOS, and UP_E1_AIS. If these alarms do not exist, go to 3.
  3. Check whether services are correctly configured. If the configuration is incorrect, modify it and issue the correct configuration. If the configuration is correct, go to 4.
  4. Cold reset the faulty board. If the TU_LOP_VC12 alarm persists, go to 5. If the alarm is cleared, no further action is required.

    Cold resetting or replacing a board will interrupt services. The operation is risky.

  5. Replace the faulty cross-connect board. If the TU_LOP_VC12 alarm persists, contact Huawei technical support engineers to handle the alarm.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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