Figure 6: Nonstop Active Routing During A Switchover - Juniper EX9200 Features Manual

Chapter 7: Understanding How Nonstop Active Routing Preserves Routing Protocol Information During a Routing Engine Switchover
Copyright © 2017, Juniper Networks, Inc.

Figure 6: Nonstop Active Routing During a Switchover

The switchover process follows these steps:
When keepalives from the master Routing Engine are lost, the system switches over
1.
gracefully to the backup Routing Engine.
The Packet Forwarding Engine connects to the backup Routing Engine, which becomes
2.
the new master. Because the routing protocol process (rpd) and chassis process
(chassisd) are already running, these processes do not need to restart.
State information learned from the point of the switchover is updated in the system.
3.
Forwarding and routing are continued during the switchover, resulting in minimal
packet loss.
Peer routers (or switches) continue to interact with the routing platform as if no change
4.
had occurred. Routing adjacencies and session state relying on underlying routing
information are preserved and not reset.
CAUTION: We recommend that you do not restart the routing protocol
process (rpd) on master Routing Engine after enabling NSR, as it disrupts
the protocol adjacency/peering sessions, resulting in traffic loss.
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