When a MEP detects a fault and fault propagation is enabled for the MEP, CFM communicates the fault to the SMGR. The SMGR marks the SAP and SDP-binding as oper-down. Note that oper-down is used here in VPLS instead of ‟oper-up but faulty” in the pipe services. CFM traffic can be transmitted to or received from the SAP and SDP-binding to ensure when the fault is cleared, the SAP goes back to normal operational state.
Note that as stated in CFM connectivity fault conditions, a fault is raised whenever a remote MEP is down (not all remote MEPs have to be down). When it is not desirable to trigger fault handling actions in some cases when a down MEP has multiple remote MEPs, operators can disable fault propagation for the MEP.
If the MEP is a down MEP, SMGR performs the fault handling actions for the affected services. Local actions done by the SMGR include (but are not limited to):
Flushing MAC addresses learned on the faulty SAP and SDP-binding.
Triggering transmission of MAC flush messages.
Notifying MSTP/RSTP about topology change. If the VPLS instance is a management VPLS (mVPLS), all VPLS instances that are managed by the m VPLS inherits the MSTP/RSTP state change and react accordingly to it.
If the service instance is a B-VPLS, and fault-propagation-bmac address(es) is/are configured for the SAP and SDP-binding, SMGR performs a lookup using the B-MAC address(es) to find out which pipe services need to be notified, then propagates a fault to these services. There can be up to four remote B-MAC addresses associated with an SAP and SDP-binding for the same B-VPLS.