NSR for IGMP

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 IGMP in connection with Protocol Independent Multicast (PIM). The primary Routing Engine uses IGMP to determine its PIM multicast state, and this IGMP-derived information is replicated on the backup Routing Engine. IGMP on the new primary Routing Engine (after failover) relearns the state information quickly through the IGMP operation. In the interim, the new primary Routing Engine retains the IGMP-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 IGMP configuration is required.