The answer is that asymmetric traffic and a PPPoE interface are the two factors that cause unequal distribution in SD-WAN volume load balancing. The volume algorithm relies on a weighted distribution of bytes across members, but asymmetric traffic disrupts this by creating sessions on different members than expected, skewing the balance. Additionally, a PPPoE interface introduces NAT constraints that prevent it from participating in load balancing, effectively removing it from the pool and causing uneven traffic flow. On the Fortinet NSE 7 Advanced Security NSE7 exam, this concept tests your understanding of how real-world network conditions—like asymmetric routing and interface limitations—override the algorithm’s intended behavior. A common trap is assuming volume balancing always distributes equally, but remember it is weighted, not strictly equal. Memory tip: think “AS-PPP” for Asymmetric traffic and PPPoE—two culprits that break the volume balance.
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 network administrator is troubleshooting an SD-WAN setup where traffic from a specific application is not being load-balanced as expected. The SD-WAN rule uses the 'volume' load balancing algorithm. Which TWO factors could cause traffic to not be distributed equally? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
One of the SD-WAN members is a PPPoE interface
Volume algorithm uses a weighted distribution. If one member is a PPPoE interface, it cannot be used for load balancing due to NAT issues. Also, if traffic is asymmetric, the session may not be balanced properly.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The SD-WAN rule is configured with 'mode = load-balance' but the algorithm is set to 'source-dest-ip'
Why it's wrong here
Algorithm is volume, not source-dest-ip.
✓
One of the SD-WAN members is a PPPoE interface
Why this is correct
PPPoE interfaces are not supported for load balancing in SD-WAN.
Related concept
Static NAT maps one inside address to one outside address.
✗
The performance SLA has a high packet loss threshold causing the member to be dead
Why it's wrong here
If member is dead, it won't receive traffic, but that's not about volume imbalance.
✓
The traffic is asymmetric, causing sessions to be created on different members than expected
Why this is correct
Asymmetric routing can cause imbalance.
Related concept
Static NAT maps one inside address to one outside address.
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: One of the SD-WAN members is a PPPoE interface — Volume algorithm uses a weighted distribution. If one member is a PPPoE interface, it cannot be used for load balancing due to NAT issues. Also, if traffic is asymmetric, the session may not be balanced properly.
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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