NSE7 Enterprise Firewall and VDOMs Practice Question
An administrator configures inter-VDOM routing between VDOM-A and VDOM-B using a VDOM link. The default route in VDOM-A points to a next-hop router, and VDOM-B has a static route to a subnet behind VDOM-A. Users in VDOM-B cannot reach that subnet. The administrator runs 'diagnose ip route list' in both VDOMs and sees the routes are present. What is the most likely cause?
⚠ Common exam trap
Test-takers frequently assume that because routes are present and the VDOM link is up, traffic should flow automatically, forgetting that FortiGate enforces firewall policies even for inter-VDOM traffic.
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
✓
Firewall policies are missing on the VDOMs to permit traffic between the VDOM link and the destination interfaces
Even though the routes are present in both VDOMs, inter-VDOM routing via a VDOM link requires explicit firewall policies on each VDOM to permit traffic between the VDOM link interface and the destination interface. Without these policies, the FortiGate drops the traffic at the firewall layer, even though the routing table is correct. This is a common misconfiguration because VDOM links behave like physical interfaces and are subject to firewall policy enforcement.
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 VDOM link MTU is too small for the traffic
Why it's wrong here
MTU size affects packet fragmentation and large transfers, not whether routes resolve; the routes already appear in both VDOMs. A missing return route or asymmetric routing is the likely cause. MTU issues would be the suspect when large packets fail while small pings succeed.
- ✗
The VDOM link interfaces are administratively down
Why it's wrong here
Administratively down interfaces would remove the connected routes from 'diagnose ip route list', yet the administrator sees routes present in both VDOMs, so the link is passing traffic at layer 3. This option is tempting because a disabled VDOM link genuinely breaks inter-VDOM routing, but that failure would be visible in the routing table.
- ✓
Firewall policies are missing on the VDOMs to permit traffic between the VDOM link and the destination interfaces
Why this is correct
Routes exist in both VDOMs, so forwarding is resolved; the VDOM link interfaces and destination interfaces still require firewall policies to permit the traffic. Inter-VDOM routing is not implicitly allowed, so absent policies silently drop packets between VDOM-A and VDOM-B.
- ✗
The VDOMs are in different administrative domains (ADOMs) on FortiManager
Why it's wrong here
ADOM membership is a FortiManager management-plane grouping for policy packages and device assignment; it has no bearing on runtime packet forwarding between VDOMs on the same FortiGate. Tempting because ADOMs do isolate devices administratively, but routing between VDOMs is unaffected by which ADOM manages them.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.