Nonstop active routing relies on control-plane state synchronization between the primary and backup Routing Engines so that routing protocol operation can continue across a switchover. To verify whether that synchronization is occurring and to see which protocol processes are participating, Junos provides visibility into the underlying replication framework. The command show task replication displays replication status and synchronization details for replicated tasks, which commonly include routing-related processes when NSR is enabled. This output helps confirm whether the backup Routing Engine is receiving the necessary state updates and whether replication is in sync, catching up, or experiencing issues.
This is the most direct operational validation because NSR effectiveness depends on ongoing state replication. Simply checking general switchover readiness does not prove protocol state is synchronized. Likewise, listing system services does not confirm replication or identify which routing protocols are actively supported for nonstop behavior. High availability statistics under services are oriented toward service-specific HA functions and do not provide the routing protocol replication view that NSR troubleshooting typically requires.
In data center fabrics where underlay routing stability is critical, routinely checking task replication status is a practical way to verify that NSR is actually providing the intended resilience before you perform maintenance or experience an unplanned Routing Engine event.
Verification sources from Juniper documentation
https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/nonstop-active-routing-understanding.html
https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/reference/command/show-task-replication.html
