CFM Service Fault Troubleshooting Guide

Discussion created by fvalcho on Oct 7, 2016

     I've used this CFM guide for several years to aid in my troubleshooting of CCM/CFM. Can anyone add to tfhis, or comment to it's correctness? I am sure there have been changes. This was originally written while testing SDS devices (393x) back in the day.

CFM SERVICE FAULTS and Fault Creations

         XC    CCM Cross Connect Defect indicates misconfiguration of MAID or MD Level.  When a CCM has an incorrectly configured MAID or MD level, it triggers a Cross Connect Defect (XC) fault.  However, this CCM is still counted as a valid CCM, and will increment the valid received (Rx) statistics counter.

4        CC    Error CCM Defect indicates mis-configuration of MEPID or CCM-Interval.

1        RD    Remote Defect Indicator shows that the remote MEP is not receiving CCMs from some other MEP in the service.  In CFM-PBT services, an RDI fault indicates that only one of the tunnels in the pair has faulted, and that traffic is only flowing in one direction.

               (remote partner conversation not stable yet)

3        RM    Remote MEP CCM Defect indicates that the local MEP is not receiving CCMs from Remote MEP(s).

               (If no partner=RM fault); (or higher MEP blocking)

2        MS    MAC Status old Defect, indicates the remote MEP transmitted CCM for a non-forwarding interface (Not applicable for PBT CFM services).

         PS    Port Status – Indicates that one of more Remote MEPs reside in a parts that are not forwarding.

6        IN    A new service initially has the Instability (IN) service fault until a stable remote MEP is detected.  The service should not have any failures after the remote MEP is detected and determined to be stable.  This fault cannot be suppressed by the alarm priority setting, and will always be reported.

         IS    Instability, (like vlan missing port) – Indicates that the service has yet to discover a stable Remote MEP.  Faults indicated here may not have been reported through a service fault event, as that requires a fault to have a priority greater than the service alarm-priority and be present for a period of time longer than the service alarm-time. A CFM service that is completely healthy will not have any Service Fault indicators.  Some service fault conditions may be expected.  For example, if a service has a Remote MEP in a port that is disabled, then the PS fault will always be present.


Several CFM Error Creation methods:

  2. Disabling PBT remote partner port cause RM fault
  3. Disabling remote partner port cause RM fault, after CFM service established.  If port disabled BEFORE CFM service established then IS FAULTS will never clear.
  4. Disabling remote partner port cause PS fault, after CFM service established
  5. Deleted MIP’s and services on -02 produced an RM fault
  6. Putting services back on -01 resolves RM fault on -02. (DON’T NEED MIPs to resolve fault-do need MIPs to see FastPath)
  7. Disable remote partner service and local service shows RM fault.

With 2 services running, deleting one service causes XC fault until other end service deleted.

  1. XC – Up MEP on NNI port when should be UNI

or, MEP numbers crossed.

  1. RDI – some MEP in MA is not sending PDU’s