The answer is Spillover. This algorithm is the correct choice because it prioritizes the link with the highest bandwidth for bulk downloads, using it until its capacity is exhausted, and then automatically fails over all traffic to the backup link when the primary link becomes unavailable. On the Fortinet NSE 7 Advanced Security NSE7 exam, this question tests your understanding of SD-WAN load balancing algorithms in a bandwidth failover scenario, where Spillover differs from Volume or Session-based methods by focusing on link capacity thresholds rather than traffic distribution. A common trap is confusing Spillover with Lowest Cost, but remember: Spillover is about bandwidth exhaustion, not cost. For a quick memory tip, think "Spillover spills traffic when the bucket is full."
NSE7 Advanced Networking and SD-WAN Practice Question
This NSE7 practice question tests your understanding of advanced networking and sd-wan. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is configured with two ISPs in an SD-WAN. The administrator wants to use the link with the highest bandwidth for bulk downloads, but if that link fails, all traffic should automatically use the backup link. Which load balancing algorithm should be used?
Why wrong: Sessions balances based on number of sessions, not bandwidth.
B
Volume
Why wrong: Volume balances based on bytes transferred, but does not provide failover.
C
Spillover
Spillover uses a configured bandwidth threshold; traffic is sent to the primary link until it reaches the threshold, then spills over to the backup. If the primary fails, all traffic goes to backup.
D
Source-destination IP
Why wrong: This algorithm hashes based on IP pairs, and does not consider bandwidth or failover in the described manner.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Spillover
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Sessions
Why it's wrong here
Sessions balances based on number of sessions, not bandwidth.
✗
Volume
Why it's wrong here
Volume balances based on bytes transferred, but does not provide failover.
✓
Spillover
Why this is correct
Spillover uses a configured bandwidth threshold; traffic is sent to the primary link until it reaches the threshold, then spills over to the backup. If the primary fails, all traffic goes to backup.
Related concept
Static NAT maps one inside address to one outside address.
✗
Source-destination IP
Why it's wrong here
This algorithm hashes based on IP pairs, and does not consider bandwidth or failover in the described manner.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE7 NAT questions on configuration and troubleshooting.
Advanced Networking and SD-WAN — This question tests Advanced Networking and SD-WAN — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Spillover
What should I do if I get this NSE7 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE7 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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