The answer is to create a Central SNAT rule with a Dynamic IP Pool using overload. This configuration is correct because overload, also known as Port Address Translation (PAT), allows the FortiGate to map all internal users from the 10.0.0.0/8 subnet to the single public IP 203.0.113.10 by dynamically assigning unique source ports to each session, enabling many-to-one NAT without exhausting IP addresses. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding of Central NAT versus policy-based NAT, with the key trap being that a static IP pool would fail because it requires a one-to-one mapping of private to public IPs, which is impossible with a single address. Remember the memory tip: "Overload = One IP, Many Ports" to instantly recall that overload is the only way to share a single public IP among thousands of internal hosts.
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. 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 administrator needs to ensure that all internal users (10.0.0.0/8) accessing the internet use a single public IP address 203.0.113.10 for source NAT. Which NAT configuration should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a Central SNAT rule with a Dynamic IP Pool using overload
Option A is correct because Central SNAT with a Dynamic IP Pool using overload (Port Address Translation) allows all internal users in 10.0.0.0/8 to share a single public IP (203.0.113.10) by dynamically mapping multiple private source IPs and ports to unique source ports on the public IP. This is the standard method for many-to-one NAT, ensuring all outbound internet traffic appears from the same public address.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create a Central SNAT rule with a Dynamic IP Pool using overload
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse enabling NAT on the interface policy (Option B) with using a specific IP pool, not realizing that interface NAT uses the interface's own IP and cannot force a different public address without an explicit IP pool.
Trap categories for this question
Scenario analysis trap
Fixed port range is used for specific scenarios like SIP; not for sharing one IP among many users.
Detailed technical explanation
How to think about this question
Central SNAT rules in FortiGate are processed before firewall policies and support IP pools with overload (PAT) to translate many private IPs to a single public IP by modifying the source port. The overload method uses the full 16-bit port range (excluding reserved ports) to multiplex up to ~65,000 concurrent sessions per public IP, which is essential for large internal networks. In contrast, interface NAT without an IP pool would use the egress interface's primary IP, which may not match the required 203.0.113.10.
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a Central SNAT rule with a Dynamic IP Pool using overload — Option A is correct because Central SNAT with a Dynamic IP Pool using overload (Port Address Translation) allows all internal users in 10.0.0.0/8 to share a single public IP (203.0.113.10) by dynamically mapping multiple private source IPs and ports to unique source ports on the public IP. This is the standard method for many-to-one NAT, ensuring all outbound internet traffic appears from the same public address.
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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Question Discussion
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