NSR for MLD

Nonstop active routing (NSR) configurations include two Routing Engines that share information so that routing is not interrupted during Routing Engine failover. These NSR configurations include passive support with Multicast Listener Discovery (MLD) in connection with Protocol Independent Multicast (PIM). The primary Routing Engine uses MLD to determine its PIM multicast state, and this MLD-derived information is replicated on the backup Routing Engine. MLD on the new primary Routing Engine (after failover) relearns the state information quickly through the MLD operation. In the interim, the new primary Routing Engine retains the MLD-derived PIM state as received by the replication process from the old primary Routing Engine. This state information times out unless refreshed by IGMP on the new primary Routing Engine. No additional MLD configuration is required.