The answer is to disable 'Allow Offload' in the firewall policy advanced options or to set the policy inspection mode to Proxy-Based. NPU offloading bypasses the CPU, allowing SIP traffic to skip deep packet inspection entirely, which is why IPS profiles fail to analyze VoIP packets. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding of how hardware acceleration can interfere with application-layer security, and the common trap is assuming that disabling offloading globally is required when a per-policy toggle exists. To remember this, think of the mnemonic “POP” — Proxy-Based or Offload disabled in the Policy — as the two reliable ways to force SIP traffic through software-based IPS inspection.
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
An administrator notices that VoIP traffic (SIP) is not being inspected by the IPS profile applied to the firewall policy. The administrator suspects the traffic is being accelerated by NPU offloading. Which TWO actions can prevent NPU offloading for SIP traffic to ensure IPS inspection? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the policy inspection mode to 'Proxy-Based'
Disabling NPU offloading per policy can be done by configuring the policy to use 'Proxy-Based' inspection or by disabling 'capwap' and 'offload' options in the firewall policy advanced settings. Also, enabling SSL inspection forces software processing.
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.
✓
Change the policy inspection mode to 'Proxy-Based'
Why this is correct
Proxy-based inspection cannot be offloaded.
Related concept
Static NAT maps one inside address to one outside address.
✓
Disable 'Allow Offload' in the policy advanced options
Why this is correct
Disabling offload forces traffic to CPU for inspection.
Related concept
Static NAT maps one inside address to one outside address.
✗
Enable 'Set SNAT' on the policy
Why it's wrong here
SNAT doesn't affect offloading.
✗
Enable 'Deep Inspection' on the policy
Why it's wrong here
Deep inspection for SSL may force software but not for SIP.
✗
Create a separate VIP for SIP
Why it's wrong here
VIP doesn't affect offloading.
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 NSE4 NAT questions on configuration and troubleshooting.
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Change the policy inspection mode to 'Proxy-Based' — Disabling NPU offloading per policy can be done by configuring the policy to use 'Proxy-Based' inspection or by disabling 'capwap' and 'offload' options in the firewall policy advanced settings. Also, enabling SSL inspection forces software processing.
What should I do if I get this NSE4 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 NSE4 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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