NSE7 Advanced Networking and SD-WAN Practice Question
An administrator configures BFD on a FortiGate to improve convergence time for OSPF. What is the primary purpose of BFD in this context?
⚠ Common exam trap
Candidates often confuse BFD's fast detection with OSPF's own hello mechanism, thinking BFD replaces or modifies OSPF timers, when in fact BFD works in parallel and triggers OSPF state changes only after a failure is detected.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
To detect link failures faster than OSPF hello timers
BFD (Bidirectional Forwarding Detection) provides sub-second link failure detection, typically in the range of 50-300 milliseconds, which is significantly faster than OSPF's default hello/dead intervals (e.g., 10/40 seconds for broadcast networks). By integrating BFD with OSPF, the FortiGate can trigger OSPF neighbor state changes and route convergence almost immediately upon a link failure, without waiting for OSPF's own hello timer expiration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
To reduce the number of OSPF neighbors
Why it's wrong here
BFD does not affect neighbor count.
- ✗
To encrypt OSPF packets
Why it's wrong here
BFD does not encrypt; it is a detection protocol.
- ✓
To detect link failures faster than OSPF hello timers
Why this is correct
BFD provides rapid failure detection, often sub-second, improving convergence.
- ✗
To load balance OSPF traffic across multiple links
Why it's wrong here
BFD is for detection, not load balancing.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE7 practice question is part of Courseiva's free Fortinet certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NSE7 exam.