NSE7 Advanced Networking and SD-WAN Practice Question
Which of the following is the primary purpose of BFD (Bidirectional Forwarding Detection) on a FortiGate?
⚠ Common exam trap
Many exam-takers confuse BFD with routing protocol keepalives or assume it performs routing table synchronization, when in fact BFD is purely a fast failure detection mechanism that operates independently of the routing protocol.
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 provide fast detection of link failures
BFD (Bidirectional Forwarding Detection) is a lightweight protocol designed to provide sub-second failure detection between two forwarding engines, such as FortiGate peers. Unlike routing protocol hellos (e.g., OSPF Hello at 10-second intervals), BFD can detect link or neighbor failures in as little as 50–100 ms, enabling faster convergence. This makes it the primary mechanism for rapid link failure detection in high-availability and SD-WAN deployments.
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 synchronize routing tables between peers
Why it's wrong here
Synchronization is done by the routing protocol itself.
- ✗
To load balance traffic across multiple paths
Why it's wrong here
Load balancing is done by routing policies or ECMP, not BFD.
- ✓
To provide fast detection of link failures
Why this is correct
BFD detects failures in sub-second intervals, much faster than routing protocol timers.
- ✗
To encrypt routing updates between peers
Why it's wrong here
Encryption is done by protocols like IPsec, not BFD.
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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.