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Nonstop Active Routing BFD Support

Nonstop active routing supports the bidirectional forwarding detection (BFD) protocol, which uses the topology discovered by routing protocols to monitor neighbors. The BFD protocol is a simple hello mechanism that detects failures in a network. Because BFD is streamlined to be efficient at fast liveliness detection, when it is used in conjunction with routing protocols, routing recovery times are improved. With nonstop active routing enabled, BFD session states are not restarted when a Routing Engine switchover occurs.

Note: BFD session states are saved only for clients using aggregate or static routes or for BGP, IS-IS, or OSPF/OSPFv3.

When a BFD session is distributed to the Packet Forwarding Engine, BFD packets continue to be sent during a Routing Engine switchover. If non-distributed BFD sessions are to be kept alive during a switchover, you must ensure that the session failure detection time is greater than the Routing Engine switchover time. The following BFD sessions are not distributed to the Packet Forwarding Engine: multi-hop sessions, tunnel-encapsulated sessions, and sessions over aggregated Ethernet and Integrated Routing and Bridging (IRB) interfaces.

Note: For BFD sessions to remain up during a Routing Engine switchover event when nonstop active routing is configured, the value for the minimum-interval configuration statement (a BFD liveness detection parameter) must be at least 2500 msec for Routing Engine-based sessions and at least 10 msec for distributed BFD sessions.

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