A company plans to include Nonstop Forwarding and Bidirectional Forwarding Detection as a part of their network redundancy plan. In which two ways do NSF and BFD work together when different…

NSF does not universally guarantee BFD session continuity during failover - whether BFD survives a supervisor restart depends entirely on the hardware platform and where BFD processing is performed.

On certain hardware platforms, BFD and NSF cannot operate together during a supervisor or routing engine failover because BFD is processed at the supervisor level - when it restarts, BFD sessions drop and the peer router will withdraw routes, disrupting forwarding.

To prevent the BFD peer from triggering a link-down during NSF, BFD packets must continue to be sent without interruption - on platforms where BFD is offloaded to line cards, this is possible, but on platforms where it is not, special configuration or feature limitations apply.

BFD is not always processed at the line cards - on many platforms it is handled by the supervisor or routing engine, so stating it is always at the line cards is factually incorrect.

BFD is not always processed at the supervisor or routing engine - on platforms that support hardware-offloaded BFD, it runs on line cards and survives supervisor failover, making this absolute statement incorrect.