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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The LFA alarm indicates that basic frames fail to be delimited in the local IMA link.


Alarm Severity Alarm Type


Communication alarm



Impact on the System

  • The E1 link that reports the alarm is unavailable and fewer links in the IMA group are available. If the service bandwidth configured for the IMA group is higher than that provided by the available E1 links in the IMA group, a congestion event occurs at the IMA port. Consequently, user cells are lost.
  • Services are interrupted if the VCTRUNK link binds only one member.

Possible Causes

Possible causes of the LFA alarm are as follows:

  • Abnormal service traffic from the cross-connection side makes the E1 deframing module on the IMA board fail to delimit the frames. Consequently, an alarm indicating loss of cell delimitation is reported. For example, the cross-connections are not configured, or some alarms, such as the TU_LOP or TU_AIS, occur.
  • VC-12 cross-connection configurations are incorrect.
  • The E1 mapping chip on an ATM board is faulty.
  • A board is faulty.


  1. On the U2000, check whether an alarm indicating no cross-connections, TU_LOP, or TU_AIS alarm is reported. If yes, clear the alarm. Check whether the LFA alarm is cleared.
  2. If the LFA alarm persists, check whether VC-12 cross-connections are correctly configured on the U2000. If not, rectify the VC-12 cross-connections and check whether the LFA alarm is cleared.
  3. If the LFA alarm persists, the E1 mapping chip on the alarmed board may be faulty. Reset (cold) the board and check whether the LFA alarm is cleared.

    If the services on the alarmed board are not configured with protection, the services are interrupted after the board cold reset.

  4. If the LFA alarm persists, replace the board that generates the LFA alarm.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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