NSE7 Advanced Networking and SD-WAN Practice Question
A FortiGate is configured with ECMP load balancing for multiple equal-cost routes. The administrator wants to ensure that all packets belonging to the same session go out the same interface. Which ECMP load balancing method should be used?
⚠ Common exam trap
Test-takers frequently confuse 'source-dest-IP-based' with 'source-IP-based' or assume that any ECMP method inherently preserves session affinity, but only the source-dest-IP-based (or per-flow) method guarantees that all packets of a session use the same interface.
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
✓
Source-dest-IP-based
Source-dest-IP-based ECMP (often called per-flow load balancing) uses a hash of both source and destination IP addresses to consistently map all packets of a session to the same next-hop interface. This ensures session integrity because the hash remains constant for the entire flow, preventing out-of-order delivery or packet drops that would occur if packets from the same session took different paths.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Weighted
Why it's wrong here
Weighted load balancing does not guarantee session affinity.
- ✓
Source-dest-IP-based
Why this is correct
Source-dest-IP hashing ensures that all packets in a session (same src/dst) go through the same interface, maintaining session integrity.
- ✗
Source-IP-based
Why it's wrong here
Source-IP only uses source IP, which can cause session asymmetry if destination changes.
- ✗
Spillover
Why it's wrong here
Spillover is not an ECMP method; it's an SD-WAN algorithm.
Go deeper
Related to this question
About these practice questions
Courseiva writes every NSE7 question from scratch — 940 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.