- A
Enable NAT on the policies to translate addresses between VLANs
Why wrong: NAT is not typically used in transparent mode for inter-VLAN traffic; it would be layer 2 forwarding.
- B
Assign an IP address to each VLAN subinterface for management
In transparent mode, each VLAN subinterface typically gets an IP for management, but for traffic forwarding, the FortiGate needs to be in the VLANs. Actually, a management IP is required for the VDOM, but not necessarily on each VLAN? In transparent mode, you set a management IP for the VDOM, but traffic forwarding between VLANs requires the FortiGate to have interfaces in both VLANs. So subinterfaces are needed, and they usually have IPs assigned for management, but forwarding itself uses layer 2. However, to perform any layer 3 inspection, the FortiGate needs IPs on the subnets. So likely needed.
- C
Create VLAN subinterfaces on the physical interface for each VLAN
VLAN subinterfaces are needed to participate in each VLAN.
- D
Create firewall policies to allow traffic between the VLANs
Firewall policies control traffic forwarding even in transparent mode.
- E
Configure static routes to route between VLANs
Why wrong: Transparent mode does not route; it bridges. So no routing needed.
Quick Answer
The answer is that creating firewall policies to allow traffic between the VLANs is one of three required configurations for transparent mode VLAN forwarding on a FortiGate. In transparent mode, the FortiGate operates as a Layer 2 bridge, so it does not route between VLANs; instead, you must create VLAN subinterfaces on the physical interface to tag and separate traffic, assign an IP address to each subinterface for management access, and then apply firewall policies to control and permit the Layer 2 forwarded frames between those VLANs. On the Fortinet NSE 4 exam, this question tests your understanding that transparent mode still enforces security policies even without routing, and a common trap is assuming that simply creating subinterfaces is enough without also configuring the policies. Remember the mnemonic “VIF-P” for VLAN subinterfaces, IP for management, and Firewall policies to allow traffic.
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. 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.
An administrator is configuring a FortiGate in transparent mode and needs to forward traffic between two VLANs. Which three configurations are required? (Choose three.)
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
Assign an IP address to each VLAN subinterface for management
In transparent mode, FortiGate acts as a Layer 2 bridge, so VLAN subinterfaces must be created on the physical interface to tag and separate traffic for each VLAN (Option C). An IP address must be assigned to each VLAN subinterface for management access (Option B), as the FortiGate does not route between VLANs at Layer 3 but still needs an IP to be reachable for administration. Firewall policies are required to control and allow traffic between VLANs (Option D), even in transparent mode, because the FortiGate applies security rules to Layer 2 forwarded frames.
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.
- ✗
Enable NAT on the policies to translate addresses between VLANs
- ✓
Assign an IP address to each VLAN subinterface for management
Why this is correct
In transparent mode, each VLAN subinterface typically gets an IP for management, but for traffic forwarding, the FortiGate needs to be in the VLANs. Actually, a management IP is required for the VDOM, but not necessarily on each VLAN? In transparent mode, you set a management IP for the VDOM, but traffic forwarding between VLANs requires the FortiGate to have interfaces in both VLANs. So subinterfaces are needed, and they usually have IPs assigned for management, but forwarding itself uses layer 2. However, to perform any layer 3 inspection, the FortiGate needs IPs on the subnets. So likely needed.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Create VLAN subinterfaces on the physical interface for each VLAN
Why this is correct
VLAN subinterfaces are needed to participate in each VLAN.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Create firewall policies to allow traffic between the VLANs
Why this is correct
Firewall policies control traffic forwarding even in transparent mode.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure static routes to route between VLANs
Why it's wrong here
Transparent mode does not route; it bridges. So no routing needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume transparent mode requires routing or NAT for inter-VLAN communication, but FortiGate in transparent mode bridges VLANs at Layer 2, relying on an external router for Layer 3 forwarding.
Detailed technical explanation
How to think about this question
In transparent mode, the FortiGate operates as a bump-in-the-wire, processing frames without modifying IP headers; VLAN subinterfaces use 802.1Q tagging to separate broadcast domains, and management IPs are assigned to these subinterfaces to allow administrative access via protocols like SSH or HTTPS. Firewall policies in transparent mode can filter based on Layer 2 headers (e.g., MAC addresses) and Layer 3/4 information, but the device never performs routing or NAT unless explicitly configured with a virtual IP or policy-based NAT. A common real-world scenario is deploying a transparent FortiGate between a switch and a router to inspect inter-VLAN traffic without redesigning the IP subnet scheme.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
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FAQ
Questions learners often ask
What does this NSE4 question test?
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Assign an IP address to each VLAN subinterface for management — In transparent mode, FortiGate acts as a Layer 2 bridge, so VLAN subinterfaces must be created on the physical interface to tag and separate traffic for each VLAN (Option C). An IP address must be assigned to each VLAN subinterface for management access (Option B), as the FortiGate does not route between VLANs at Layer 3 but still needs an IP to be reachable for administration. Firewall policies are required to control and allow traffic between VLANs (Option D), even in transparent mode, because the FortiGate applies security rules to Layer 2 forwarded frames.
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 →
Same concept, more angles
1 more ways this is tested on NSE4
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An administrator is configuring a VLAN interface on a FortiGate. The physical interface is port2 and the VLAN ID is 100. Which of the following correctly creates the VLAN interface?
easy- ✓ A.config system interface edit port2.100 set vlanid 100 set type vlan next end
- B.config system interface edit port2 set vlanid 100 next end
- C.config system interface edit port2.100 set type vlan next end
- D.config system vlan edit port2.100 set vlanid 100 next end
Why A: Option A is correct because it uses the correct CLI syntax to create a VLAN subinterface on a FortiGate. The command `config system interface` enters the interface configuration context, `edit port2.100` creates or edits the subinterface named with the physical interface and VLAN ID, `set vlanid 100` assigns the VLAN tag, and `set type vlan` explicitly defines the interface type as VLAN. This matches the required configuration for 802.1Q VLAN tagging on FortiGate.
Last reviewed: Jun 24, 2026
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