The answer is Type: One-to-One and External IP Range 203.0.113.20-203.0.113.30. This configuration is correct because a one-to-one NAT IP pool on a FortiGate ensures that each internal server from the 10.0.1.100-10.0.1.110 range is permanently mapped to a unique public IP without using port address translation, satisfying the requirement for fixed, non-overloaded mapping. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this question tests your understanding of IP Pool types and their behavior under source NAT, specifically distinguishing One-to-One from Overload or Fixed Port Range. A common trap is selecting “Dynamic IP Allocation” or “Fixed Port Range,” which would either break the one-to-one requirement or introduce PAT. Remember the memory tip: “One-to-One means one internal IP gets one external IP—no port sharing, just a straight swap.”
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 configure source NAT for a group of internal servers (10.0.1.100-10.0.1.110) so that each server uses a unique public IP from the range 203.0.113.20-203.0.113.30. The requirement is that each internal IP maps to a fixed external IP (one-to-one mapping) and not port overload. Which TWO settings should be configured in the IP Pool? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
External IP Range: 203.0.113.20-203.0.113.30
Option C is correct because the External IP Range must be set to 203.0.113.20-203.0.113.30 to define the pool of public IPs that will be mapped one-to-one to the internal servers. Option D is correct because Type: One-to-One ensures each internal IP is permanently mapped to a unique external IP, without port address translation (PAT), meeting the requirement of fixed one-to-one mapping.
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.
✗
Type: Overload
Why it's wrong here
Overload uses one IP for many internal hosts.
✗
Enable 'Fixed Port Range'
Why it's wrong here
Fixed port range is for overload with port range, not one-to-one.
Read the scenario before looking for a memorised answer.
✓
Type: One-to-One
Why this is correct
One-to-One maps each internal IP to a unique external IP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Central SNAT instead of IP Pool
Why it's wrong here
Central SNAT can also do one-to-one but the question asks about IP Pool.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'One-to-One' with 'Overload' and select 'Type: Overload' thinking it still provides unique IPs, but Overload always uses PAT and cannot guarantee a fixed external IP per internal host.
Detailed technical explanation
How to think about this question
In FortiGate, One-to-One NAT (Type: One-to-One) performs static mapping without port translation, so each internal IP is directly translated to a specific external IP from the defined range. This is implemented by creating a one-to-one correspondence based on the order of IPs in the internal and external ranges; if the ranges are not equal in size, the mapping fails or excess IPs are unused. In real-world scenarios, this is commonly used for servers that must be reachable from the internet on standard ports without dynamic port allocation.
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: External IP Range: 203.0.113.20-203.0.113.30 — Option C is correct because the External IP Range must be set to 203.0.113.20-203.0.113.30 to define the pool of public IPs that will be mapped one-to-one to the internal servers. Option D is correct because Type: One-to-One ensures each internal IP is permanently mapped to a unique external IP, without port address translation (PAT), meeting the requirement of fixed one-to-one mapping.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.