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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The LOOP_ALM is a loopback alarm. This alarm occurs when service loopback is set.


Alarm Severity Alarm Type


Equipment 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 loopback mode.

  • 0x00: Optical/electrical port inloop.
  • 0x01: Optical/electrical port outloop.
  • 0x02: Path inloop.
  • 0x03: Path outloop.
  • 0x04: Loopback on the user side.
  • 0x05: Loopback on the combination wave side.
  • 0x06: SPI inloop.
  • 0x07: SPI outloop.
  • 0x08: ATM layer inloop.
  • 0x09: ATM layer outloop.
  • 0x0A: PHY layer inloop.
  • 0x0B: PHY layer outloop.
  • 0x0C: MAC layer inloop.
  • 0x0D: MAC layer outloop.
  • 0x0E: VC-4 timeslot inloop.
  • 0x0F: VC-4 timeslot outloop.
  • 0x10: VC-3 timeslot inloop.
  • 0x11: VC-3 timeslot outloop.
  • 0x12: VC-12 timeslot inloop.
  • 0x13: VC-12 timeslot outloop.
  • 0x14: IF outloop.
  • 0x15: IF inloop.
  • 0x16: RF inloop.
  • 0xff: Any of the preceding loopback modes.

Impact on the System

The alarm indicates that an optical port loopback or path loopback is configured on a line board or a tributary board. If the setting is not canceled, services may be interrupted.

Possible Causes

Possible causes of the LOOP_ALM alarm are as follows:

  • Inloops or outloops are configured on a board.
  • A board is faulty.


  1. Set the loopback status of the alarmed port to no loop. Check whether the alarm is cleared.

    If... Then...

    The alarm persists

    Go to the next step.

    The alarm is cleared

    No further action is required.

  2. Replace the alarmed board.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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