350-501 Networking Practice Question
A service provider is running OSPF in their core network. After a link failure, routing convergence is taking longer than expected. The engineer suspects the issue is related to the SPF calculation. Which OSPF feature can reduce the SPF calculation time?
⚠ Common exam trap
Cisco often tests the distinction between fast failure detection (BFD) and fast SPF calculation (iSPF), leading candidates to mistakenly choose BFD when the question specifically asks about reducing SPF calculation time.
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
✓
Incremental SPF (iSPF)
Incremental SPF (iSPF) reduces SPF calculation time by recalculating only the affected portion of the Shortest Path Tree (SPT) after a topology change, rather than recomputing the entire tree. This is especially beneficial in large OSPF networks where full SPF runs are CPU-intensive and slow convergence.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
OSPF database overload protection
Why it's wrong here
Protects against excessive LSAs, does not reduce SPF time.
- ✗
Bidirectional Forwarding Detection (BFD)
Why it's wrong here
Provides fast failure detection, but does not affect SPF calc.
- ✓
Incremental SPF (iSPF)
Why this is correct
Reduces SPF computation by recalculating only changed parts.
- ✗
LSA pacing timers (pacing-interval)
Why it's wrong here
Controls LSA generation rate, not SPF calculation.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 practice question is part of Courseiva's free Cisco 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 350-501 exam.