You have configured BFD for OSPF on a CX switch and have noticed the BFD session stays down but the OSPF neighbor state is up. What could explain this behavior?
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Reference / correct answer:
The remote switch does not support BFD.
Most accepted answer: A. The remote switch does not support BFD.
Community votes: A=2, C=1, D=1
Selected Answer: C It is C -> A very common misconfiguration is enabling BFD only at the OSPF level (bfd all-interfaces or ip ospf bfd) while forgetting the global bfd command. In that case: OSPF continues to form and maintain its neighbor relationship normally — OSPF adjacency doesn't depend on BFD; it uses its own Hello/Dead timer mechanism independently. BFD itself never actually starts running on the switch, so no BFD session can ever come up locally — resulting in exactly the symptom described: BFD session down, but OSPF neighbor state up. upvoted 1 times
Selected Answer: A If an OSPF neighbor does not support BFD, the switch continues to try to establish a BFD session with that neighbor. It lists the session as down, but because the session was never up, the down state does not cause the switch to tear down the neighbor relationship. Alpizar, Ivannia; Almeida, Henrique; Sathe, Mugdha; Puduchery, Venu Dhanraj . HPE Aruba Networking Certified Professional - Switching : Official Certification Study Guide (HPE7-A08) (pp. 263-264). HPE Press. Kindle Edition. upvoted 1 times
Selected Answer: A I now think the Correct is 'A'. If OSPF v2 to v3 mismatch then the OSFP neighbour state would be down also. upvoted 2 times
Selected Answer: D I don't think answer is B. But correct answers could be A or D. BFD is definetely supported on OSFP broadcast links so answer cannot be B. upvoted 1 times