CFM Alarms

Alarm Types

If CFM detects a fault in an E2E link, it triggers an alarm and sends the alarm to the network management system (NMS). A network administrator uses the information to troubleshoot. Table 1 describes alarms supported by CFM.

**Table 1** Alarms supported by CFM
Alarm Name	Description
hwDot1agCfmUnexpectedMEGLevel	A MEP receives a CCM frame with an incorrect MEG level.
hwDot1agCfmUnexpectedMEGLevelCleared	During an interval equal to 3.5 times the CCM transmission period, a MEP does not receive CCM frames with an incorrect MEG level.
hwDot1agCfmMismerge	A MEP receives a CCM frame with a correct MEG level but an incorrect MEG ID.
hwDot1agCfmMismergeCleared	During an interval equal to 3.5 times the CCM transmission period, a MEP does not receive CCM frames with an incorrect MEG ID.
hwDot1agCfmUnexpectedMEP	A MEP receives a CCM frame with a correct MEG level and MEG ID but an unexpected MEP ID.
hwDot1agCfmUnexpectedMEPCleared	During an interval equal to 3.5 times the CCM transmission period, a MEP does not receive CCM frames with an unexpected MEP ID.
hwDot1agCfmUnexpectedPeriod	A MEP receives a CCM frame with a correct MEG level, MEG ID, and MEP ID but a Period field value different than its own CCM transmission period.
hwDot1agCfmUnexpectedPeriodCleared	During an interval equal to 3.5 times CCM transmission period, a MEP does not receive CCM frames with an incorrect Period field value.
hwDot1agCfmUnexpectedMAC	A MEP receives a CCM carrying a source MAC address different from the locally specified RMEP's MAC address.
hwDot1agCfmUnexpectedMACCleared	The alarm about RMEP MAC inconsistency is cleared.
hwDot1agCfmLOC	During an interval equal to 3.5 times the CCM transmission period, a MEP does not receive CCM frames from a peer MEP.
hwDot1agCfmLOCCleared	During an interval equal to 3.5 times the CCM transmission period, a MEP receives n CCM frames from a peer MEP.
hwDot1agCfmExceptionalMACStatus	The interface connecting the RMEP to the MEP does not work properly based on Status type-length-value (TLV) information carried in a CCM sent by an RMEP.
hwDot1agCfmExceptionalMACStatusCleared	The interface connecting the RMEP to the MEP is restored based on Status TLV information carried in a CCM sent by an RMEP.
hwDot1agCfmRDI	A MEP receives a CCM frame with the RDI field set.
hwDot1agCfmRDICleared	A MEP receives a CCM frame with the RDI field cleared.

Alarm Anti-jitter

Multiple alarms and clear alarms may be generated on an unstable network enabled with CC. These alarms consume system resources and deteriorate system performance. An RMEP activation time can be set to prevent false alarms, and an alarm anti-jitter time can be set to limit the number of alarms generated.

**Table 2** Alarm anti-jitter
Function Setting	Description
RMEP activation time	Prevents false alarms. A local MEP with the ability to receive CCMs can accept CCMs only after the RMEP activation time elapses.
Alarm anti-jitter time	If a MEP detects a connectivity fault: It sends an alarm to the NMS after the anti-jitter time elapses. It does not send an alarm if the fault is rectified before the anti-jitter time elapses.
Alarm clearing anti-jitter time	If a MEP detects a link fault and sends an alarm: It sends a clear alarm if the fault is rectified within a specified alarm clearing anti-jitter time. It does not send a clear alarm if the fault is not rectified within a specified alarm clearing anti-jitter time.

Alarm Suppression

If different types of faults trigger more than one alarm, CFM alarm suppression allows the alarm with the highest level to be sent to the NMS. If alarms persist after the alarm with the highest level is cleared, the alarm with the second highest level is sent to the NMS. The process repeats until all alarms are cleared.

The principles of CFM alarm suppression are as follows:

Alarms with high levels require immediate troubleshooting.
A single fault may trigger alarms with different levels. After the alarm with the highest level is cleared, alarms with lower levels may also be cleared.