Assuming that there is a transition of the existing DF to non-DF status, the PE that owns the MH site experiencing this transition generates a MAC flush-all-from-me (negative MAC flush) toward the related core PEs. Upon reception, the remote PEs flush all the MACs learned from the MH PE.
MAC flush-all-from-me indication message is sent using the following core mechanisms:
For LDP VPLS running between core PEs, existing LDP MAC flush is used.
For pseudowire signaled with BGP VPLS, MAC flush is provided implicitly using the L2-Info Extended community to indicate a transition of the active MH site; for example, the attached objects going down or more generically, the entire site going from Designated Forwarder (DF) to non-DF.
Double flushing does not happen as it is expected that between any pair of PEs, there exists only one type of pseudowires – either BGP or LDP pseudowire, but not both.