The answer is that VDOMs in transparent mode are isolated Layer 2 domains, so ARP requests cannot cross VDOM boundaries. This is correct because transparent mode VDOM isolation means each VDOM operates as an independent forwarding domain with its own MAC address table and VLAN database; ARP, being a Layer 2 broadcast, is confined to the originating VDOM and never forwarded to another. On the Fortinet NSE 7 Advanced Security NSE7 exam, this question tests your understanding that transparent mode does not inherently bridge traffic between VDOMs—even on the same VLAN—and that inter-VDOM routing (Layer 3 forwarding) must be explicitly configured for any communication. A common trap is assuming that same-VLAN equals same broadcast domain across VDOMs, but the isolation is absolute at Layer 2. Memory tip: think of each VDOM as a separate physical switch—ARP broadcasts stay inside their own switch, no matter the VLAN number.
NSE7 Enterprise Firewall and VDOMs Practice Question
This NSE7 practice question tests your understanding of enterprise firewall and vdoms. 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 deploys a FortiGate in transparent mode with two VDOMs: one for the internal network and one for DMZ. The admin notices that ARP requests from internal hosts are not reaching the DMZ servers even though they are on the same VLAN. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VDOMs in transparent mode are isolated layer 2 domains; inter-VDOM routing is required for communication
In transparent mode, each VDOM acts as an independent Layer 2 forwarding domain with its own MAC address table and VLAN database. ARP requests are broadcast frames that are confined to the VDOM where they originate; they are not forwarded to other VDOMs. Therefore, even if the internal and DMZ interfaces are on the same VLAN, the ARP request from an internal host will never reach a DMZ server unless inter-VDOM routing (Layer 3 forwarding between VDOMs) is explicitly configured.
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.
✗
The FortiGate is not configured to proxy ARP
Why it's wrong here
Proxy ARP is not needed; the issue is VDOM isolation.
✓
VDOMs in transparent mode are isolated layer 2 domains; inter-VDOM routing is required for communication
Why this is correct
Correct. VDOMs separate broadcast domains.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The internal and DMZ VDOMs are in different VLANs on the same physical interface
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume transparent mode operates as a simple bridge that forwards all Layer 2 traffic between all interfaces, forgetting that VDOMs create strict Layer 2 isolation boundaries even in transparent mode.
Detailed technical explanation
How to think about this question
Under the hood, each transparent-mode VDOM maintains its own independent Layer 2 forwarding table and does not share broadcast domains. When a broadcast frame like an ARP request enters a VDOM, the FortiGate floods it only within that VDOM's interfaces. Inter-VDOM communication at Layer 2 is not possible without a Layer 3 inter-VDOM link or a VDOM link object. In real-world deployments, this design is intentional to enforce security boundaries—for example, keeping internal users and DMZ servers in separate broadcast domains even when they share a physical VLAN.
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
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.
Enterprise Firewall and VDOMs — This question tests Enterprise Firewall and VDOMs — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: VDOMs in transparent mode are isolated layer 2 domains; inter-VDOM routing is required for communication — In transparent mode, each VDOM acts as an independent Layer 2 forwarding domain with its own MAC address table and VLAN database. ARP requests are broadcast frames that are confined to the VDOM where they originate; they are not forwarded to other VDOMs. Therefore, even if the internal and DMZ interfaces are on the same VLAN, the ARP request from an internal host will never reach a DMZ server unless inter-VDOM routing (Layer 3 forwarding between VDOMs) is explicitly configured.
What should I do if I get this NSE7 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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