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 hardware platforms are compared? (Choose two.)
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A. B. C. D. E.BC.
NSF (Nonstop Forwarding) and BFD (Bidirectional Forwarding Detection) are two important features that can be used together to provide network redundancy. The NSF feature ensures that there is no network downtime during a supervisor engine or routing engine failover, and BFD provides fast detection of link failures. In this question, we are asked to determine how NSF and BFD work together when different hardware platforms are compared.
Answer option A is correct. During a supervisor engine or routing engine failover, the NSF feature ensures that the BFD at the peer router will not trigger a link down, regardless of the used hardware platform. This means that even if the supervisor engine or routing engine fails, the BFD will continue to function normally, and the peer router will not detect a link failure. This is possible because the NSF feature maintains the forwarding state of the router during the failover process.
Answer option B is incorrect. While it is true that some hardware platforms do not support BFD and NSF together, this does not mean that the BFD at the peer router will trigger a link down during a supervisor engine or routing engine failover. It simply means that the BFD feature cannot be used in conjunction with the NSF feature on those platforms.
Answer option C is correct. To ensure that BFD at the peer router will not trigger a link down during NSF, the BFD packets must be processed fast enough. During a supervisor engine or routing engine failover, the BFD packets must also be processed independently of the supervisor engine or routing engine. This can be achieved by processing BFD packets at the line cards, rather than at the supervisor engine or routing engine.
Answer option D is incorrect. While it is true that BFD packets can be processed at the line cards, this does not mean that a supervisor engine or routing engine failover will not affect the BFD peer router. If BFD packets are not processed fast enough, the peer router may detect a link failure, even if the forwarding state of the router is maintained during the failover process.
Answer option E is incorrect. BFD packets are not always processed at the supervisor engine or routing engine. Depending on the hardware platform, BFD packets may be processed at the line cards. Additionally, a supervisor engine or routing engine failover will not always trigger a link down at the peer router, as this depends on whether the BFD packets are processed fast enough and independently of the supervisor engine or routing engine.
In summary, the correct answers are options A and C. The NSF feature ensures that the BFD at the peer router will not trigger a link down during a supervisor engine or routing engine failover, regardless of the used hardware platform. To achieve this, the BFD packets must be processed fast enough and independently of the supervisor engine or routing engine.