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NSE4 · Question #519

A FortiGate unit has multiple VDOMs in NAT/route mode with multiple VLAN interfaces in each VDOM. Which of the following statements is correct regarding the IP addresses assigned to each VLAN interfac

The correct answer is C. Different VLANs can share the same IP address as long as they are in different VDOMs.. When using multiple VDOMs, VLAN interfaces in different VDOMs can share the same IP addresses because VDOMs provide complete logical separation of networking resources.

Submitted by ahmad_uae· Apr 18, 2026FortiGate Deployment and System Configuration

Question

A FortiGate unit has multiple VDOMs in NAT/route mode with multiple VLAN interfaces in each VDOM. Which of the following statements is correct regarding the IP addresses assigned to each VLAN interface?

Options

  • ADifferent VLANs can share the same IP address as long as they have different VLAN IDs.
  • BDifferent VLANs can share the same IP address as long as they are in different physical
  • CDifferent VLANs can share the same IP address as long as they are in different VDOMs.
  • DDifferent VLANs can never share the same IP addresses.

How the community answered

(31 responses)
  • A
    3% (1)
  • C
    94% (29)
  • D
    3% (1)

Why each option

When using multiple VDOMs, VLAN interfaces in different VDOMs can share the same IP addresses because VDOMs provide complete logical separation of networking resources.

ADifferent VLANs can share the same IP address as long as they have different VLAN IDs.

Within the same VDOM, even if VLANs have different IDs, each interface (physical or VLAN) must have a unique IP address within its routing instance to avoid IP conflicts.

BDifferent VLANs can share the same IP address as long as they are in different physical

Physical interfaces are irrelevant here; the isolation is at the VDOM level, not tied to physical separation of interfaces, which isn't the primary mechanism for allowing overlapping IPs.

CDifferent VLANs can share the same IP address as long as they are in different VDOMs.Correct

VDOMs create completely isolated virtual FortiGate instances, meaning that IP address spaces, routing tables, and network interfaces within one VDOM are independent of those in another, allowing for overlapping IP addresses.

DDifferent VLANs can never share the same IP addresses.

This statement is incorrect because VDOMs are specifically designed to allow for overlapping IP address spaces by creating isolated network environments.

Concept tested: FortiGate VDOM network isolation (overlapping IP addresses)

Source: https://docs.fortinet.com/document/fortigate/7.4.0/administration-guide/209971/vdom-modes

Topics

#VDOMs#VLAN Interfaces#IP Addressing#Interface Configuration

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