When using STP as described previously is not appropriate, the ‟Selective MAC flush” feature can be used instead.
In this scenario, the 7210 SAS that detects a port failure sends out a flush-all-from-ME LDP message to all PEs in the VPLS. The PEs receiving this LDP message removes all MAC entries originated by the sender from the indicated VPLS.
A drawback of this approach is that selective MAC flush does not signal that a backup path was found, only that the previous path is no longer available. In addition, the selective MAC Flush mechanism is effective only if the CE and PE are directly connected (no intermediate hubs or bridges) as it reacts only to a physical failure of the link. Consequently, Nokia recommends using the MAC flush with STP method described previously where possible.