NSE7 Enterprise Firewall and VDOMs Practice Question
An administrator is configuring a FortiGate with multiple VDOMs. The administrator wants to ensure that the VDOMs can use overlapping IP addresses on their respective interfaces. Which setting must be enabled to allow this?
⚠ Common exam trap
The trap here is thinking that overlapping subnets are allowed by default or can be enabled globally, when in fact each VDOM must have the setting enabled individually.
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
✓
Enable 'allow-subnet-overlap' in each VDOM that requires overlapping subnets.
To use overlapping IP addresses in different VDOMs, you must enable 'allow-subnet-overlap' in each VDOM that requires it. This setting allows the FortiGate to accept the same subnet on interfaces in different VDOMs. It is configured within each VDOM's system settings, not globally. This is useful in multi-tenant environments where customers may use the same private IP ranges.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Assign the interfaces to different zones within the same VDOM to allow overlapping IPs.
Why it's wrong here
Zones are used within a single VDOM to group interfaces, but they do not permit overlapping IP addresses within the same VDOM. In fact, overlapping subnets within the same VDOM are not allowed even with zones. The 'allow-subnet-overlap' setting is for different VDOMs, not for zones within a VDOM.
- ✓
Enable 'allow-subnet-overlap' in each VDOM that requires overlapping subnets.
Why this is correct
The 'allow-subnet-overlap' setting is specifically designed to permit the same subnet to be used on interfaces in different VDOMs. It must be enabled in each VDOM where overlapping addresses are needed. Without it, the FortiGate rejects the configuration because it considers the subnets conflicting.
- ✗
Configure the interfaces to use different VDOM link IP addresses to avoid overlap.
Why it's wrong here
VDOM link IP addresses are used for inter-VDOM routing and do not affect the ability to use overlapping subnets on physical interfaces. Overlapping subnets are about the same IP range on different interfaces in different VDOMs, which requires 'allow-subnet-overlap'. Using different VDOM link IPs does not address the overlap issue.
- ✗
Enable 'allow-subnet-overlap' globally in the system settings, which applies to all VDOMs.
Why it's wrong here
The 'allow-subnet-overlap' setting is not global; it is configured per VDOM. Enabling it globally is not possible. Each VDOM must have the setting enabled individually if it requires overlapping subnets. A global setting would be inefficient and is not how FortiGate implements this feature.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Fortinet exam blueprint
This NSE7 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 NSE7 exam.