Question 1hardmultiple choice
Read the full NAT/PAT explanation →Question 897 of 1,000
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A FortiGate has two WAN interfaces (wan1, wan2) configured with ECMP routes to the same destination. The administrator notices that traffic for a single session is being load-balanced across both links, causing performance issues. What should be configured to ensure sessions stick to one link?
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
✓
Change ECMP load balancing method to 'source-ip-based' or 'source-dst-ip-based'.
Option B is correct because changing the ECMP load balancing method to 'source-ip-based' or 'source-dst-ip-based' ensures that all packets belonging to the same session (identified by source IP or source-destination IP pair) are hashed to the same egress interface. This prevents a single session from being split across multiple WAN links, which can cause out-of-order packets and performance degradation. FortiGate’s ECMP hash algorithm uses the configured method to compute a hash value that deterministically selects the outgoing interface for each flow.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ECMP load balancing methods with SD-WAN stickiness features, assuming SD-WAN is required for session persistence, when in fact ECMP’s hash algorithm can be tuned directly to achieve per-session stickiness.
Detailed technical explanation
How to think about this question
Under the hood, FortiGate’s ECMP uses a hash function over the selected tuple (e.g., source IP, destination IP, or both) to compute a value that maps to one of the ECMP next hops. The default method is often 'source-dst-ip-based' in newer firmware, but if set to 'round-robin' or 'packet-based', a single session’s packets can be distributed across multiple links. In real-world scenarios, this causes TCP reordering and retransmissions, severely impacting throughput; changing to a flow-aware hash method resolves this without disabling ECMP.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Questions learners often ask
What does this NSE4 question test?
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change ECMP load balancing method to 'source-ip-based' or 'source-dst-ip-based'. — Option B is correct because changing the ECMP load balancing method to 'source-ip-based' or 'source-dst-ip-based' ensures that all packets belonging to the same session (identified by source IP or source-destination IP pair) are hashed to the same egress interface. This prevents a single session from being split across multiple WAN links, which can cause out-of-order packets and performance degradation. FortiGate’s ECMP hash algorithm uses the configured method to compute a hash value that deterministically selects the outgoing interface for each flow.
What should I do if I get this NSE4 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This NSE4 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 NSE4 exam.
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