NSE4 System and Network Administration Practice Question
A FortiGate is configured in NAT/Route mode. Which statement is correct about this mode?
⚠ Common exam trap
Many candidates confuse NAT/Route mode with Transparent mode, assuming that NAT implies bridging or that only one interface can be used, but FortiGate explicitly supports multiple routed interfaces and VLANs in this mode.
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
✓
The FortiGate routes traffic between different subnets and can perform NAT.
In NAT/Route mode, the FortiGate operates as a Layer 3 router, forwarding traffic between different subnets while also performing Network Address Translation (NAT) when configured. This is the default operational mode for most FortiGate deployments, enabling both routing and NAT capabilities on the same device.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Only one interface can be used for traffic.
Why it's wrong here
This is incorrect because NAT/Route mode is a true routing deployment in which the FortiGate can use an arbitrary number of interfaces simultaneously. You can attach multiple LAN segments, multiple WAN uplinks, and DMZ networks, and create firewall policies to forward traffic between any of those interfaces. Features such as ECMP, SD-WAN, and link failover rely on more than one active interface, so limiting to a single interface is neither a requirement nor a restriction.
- ✓
The FortiGate routes traffic between different subnets and can perform NAT.
Why this is correct
This is the correct description of NAT/Route mode, which is the default operating mode of a FortiGate. In this mode, the FortiGate acts as a Layer 3 router and makes forwarding decisions based on IP addresses and routing tables, sending packets from one subnet to another. It can also apply NAT, including source NAT for outbound Internet access and destination NAT for inbound services, as part of its firewall policies.
- ✗
VLAN interfaces are not supported in this mode.
Why it's wrong here
VLAN interfaces are absolutely supported in NAT/Route mode. You can create 802.1Q VLAN subinterfaces on a physical interface and assign each one a distinct IP address and firewall policy, allowing one port to carry multiple broadcast domains. The FortiGate routes between these VLAN subinterfaces just as it routes between physical interfaces, so VLAN support is an integral part of the mode, not an exception.
- ✗
The FortiGate acts as a Layer 2 bridge.
Why it's wrong here
This statement describes transparent mode, not NAT/Route mode. In transparent mode the FortiGate acts as an invisible Layer 2 bridge, forwarding frames based on MAC addresses and usually operating without IP addresses on its interfaces. NAT/Route mode, by contrast, operates at Layer 3, performs IP routing, and can rewrite source and destination addresses through NAT, so calling it a Layer 2 bridge is incorrect.
Visual reference
Go deeper
Related to this question
About these practice questions
This NSE4 question is part of Courseiva's 773-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
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.