OSPFv2 non-stop routing
OSPFv2 can continue operation without interruption during hitless failover when the OSPFv2 non-stop routing (NSR) feature is enabled.
During graceful restart (GR), the restarting neighbors must help build routing information during a failover. However, GR may not be supported by all devices in a network. NSR eliminates this dependency.
NSR does not require support from neighboring devices to perform hitless failover, and OSPF can continue operation without interruption.
NOTE
NSR does not support IPv6-over-IPv4 tunneling and virtual links, so traffic loss is expected while performing hitless failover.
If the active management module fails, the standby management module takes over and maintains the current OSPF routes, link-state advertisements (LSAs), and neighbor adjacencies, so that there is no loss of existing traffic to the OSPF destination.
NOTE
NSR and Graceful Restart (GR) are mutually exclusive.