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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The MAC_EXT_EXC alarm indicates that the number of bit errors at the MAC layer crosses the threshold.


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 threshold crossing type.

  • 0x01: ETHDROP threshold crossing
  • 0x02: ETHEXCCOL threshold crossing
  • 0x03: RXBBAD threshold crossing

Impact on the System

Service performance deteriorates.

Possible Causes

  • Cause 1: ETHDROP threshold crossing. The number of packet loss events crosses the upper threshold.
  • Cause 2: ETHEXCCOL threshold crossing. The number of frames unsuccessfully transmitted after successive collisions crosses the upper threshold.
  • Cause 3: RXBBAD threshold crossing. The number of received bad packets crosses the upper threshold.


  1. Check whether the working modes of the ports at the transmit and receive ends are the same.
    1. On the NMS, query the working modes of the ports at both ends.
      If... Then...
      The ports at both ends work in different modes or in half-duplex mode Set the working modes of the two ports to both full-duplex or auto-negotiation by referring to Setting the General Attributes of Ethernet Interfaces.
      The ports at both ends work in the same mode and are not working in half-duplex mode Go to the next step.
  2. Handle the packet transmission errors at the opposite end. Check whether the fiber or the optical module are normal.
    If... Then...
    faulty, Replace the fiber or the optical module.
    not faulty, Go to the next step.
  3. Check whether PLA configurations are correct. Check whether the local end reports ETH_LOS alarm caused by external line breakage or excessive attenuation.
    If... Then...
    exists, Refer to the corresponding section in this document to clear alarm.
    not exists, Go to the next step.
  4. If the board are faulty, Replace the board.
  5. Check whether alarm is cleared. If the alarm persists, contact Huawei technical support engineers to handle the alarm.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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