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The draft definition message is currently used in management VPLS which is using RSTP for
recovering from failures in Layer 2 topologies. The mechanism described in this document
represent an alternative solution.
The advantage of this approach (as compared to RSTP based methods) is that only MAC-affected
addresses are flushed and not the full forwarding database. While this method does not provide a
mechanism to secure alternative loop-free topology, the convergence time is dependent on the
speed of the given CE device will open alternative link (L2-B switch in Figure 73) as well as on
the speed PE routers will flush their FDB.
In addition, this mechanism is effective only if PE and CE are directly connected (no hub or
bridge) as it reacts to physical failure of the link.
MC-Ring and VPLS
The use of multi-chassis ring control in a combination with the plain VPLS SAP is supported FDB
in individual ring nodes in case of the link (or ring node) failure cannot be cleared.
This combination is not easily blocked in the CLI. If configured, the combination may be
functional but the switchover times will be proportional to MAC aging in individual ring nodes
and/or to relearning rate due to downstream traffic.
Redundant plain VPLS access in ring configurations, therefore, exclude corresponding SAPs from
the multi-chassis ring operation. Configurations such as mVPLS can be applied.
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