NSE4 Firewall Policies and NAT Practice Question
An administrator needs to translate a single internal server (192.168.1.10:8080) to a public IP (203.0.113.10:80) so that external users can access it via HTTP. Which type of VIP should be configured?
⚠ Common exam trap
Many candidates confuse Static NAT (one-to-one IP mapping) with Port Forwarding VIP, forgetting that Static NAT translates all ports and does not allow port remapping, while Port Forwarding VIP specifically handles port translation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Port Forwarding VIP
Port Forwarding VIP (also called DNAT or destination NAT) is the correct choice because it translates a single internal server's IP and port (192.168.1.10:8080) to a specific public IP and port (203.0.113.10:80), allowing external HTTP users to reach the internal server. This is a one-to-one mapping of a public IP:port to a private IP:port, which is the exact definition of port forwarding in FortiGate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Server Load Balancing VIP
Why it's wrong here
Server Load Balancing (SLB) VIP is incorrect because it is designed to distribute incoming traffic across a pool of multiple backend servers using scheduling algorithms like round-robin or least-connection. This scenario requires translating a single internal server, not balancing load among multiple servers. Using SLB would require defining a virtual server with a real-server pool, which adds unnecessary complexity and does not match the one-to-one service translation need.
- ✗
Virtual IP (VIP) with no port forwarding
Why it's wrong here
A Virtual IP (VIP) with no port forwarding is incorrect because it only translates the destination IP address, leaving the destination port unchanged. This means any service on the internal server would be reachable through the VIP, including unintended ports, without the ability to map an external port (e.g., 8080) to a different internal port (e.g., 80). For translating a single specific service on one internal server, port-level control is required, which this option lacks.
- ✗
Static NAT (one-to-one VIP)
Why it's wrong here
Static NAT (one-to-one VIP) is incorrect because it maps an entire external IP address to an entire internal IP address, translating all traffic without any port-specific manipulation. This approach consumes a full public IP per internal server and exposes all services on that server, which is less secure and less efficient than a port-forwarding rule. It also does not allow mapping different external ports to different internal ports, making it unsuitable for the stated requirement of translating a single internal server's specific service.
- ✓
Port Forwarding VIP
Why this is correct
Port Forwarding VIP is correct because it provides a destination NAT rule that maps a specific external IP address and port combination to a specific internal IP address and port combination. This allows an administrator to expose exactly one service (e.g., HTTPS on port 443) from a single internal server while hiding all other ports, and it conserves public IP addresses. In FortiOS, this is configured as a VIP with the 'port-forwarding' option enabled, which creates a one-to-one mapping of the destination port and optionally a different source port.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.