The answer is to create firewall policies on the hub that allow traffic between the spoke networks and configure Phase 2 selectors with 0.0.0.0/0.0.0.0 on the hub. In a hub-and-spoke IPsec VPN, the hub must have Phase 2 selectors covering all possible spoke subnets—typically using 0.0.0.0/0—so that the IPsec security associations can encapsulate traffic from any spoke destined for another spoke. Without this broad selector, the hub would only forward traffic for explicitly defined subnets, breaking spoke-to-spoke communication. Additionally, firewall policies on the hub must explicitly permit inter-spoke traffic; otherwise, even with correct Phase 2 settings, the hub will drop the packets. On the Fortinet NSE 4 exam, this tests your understanding that the hub acts as a router and must both encrypt and forward traffic between spokes. A common trap is forgetting the firewall policy, thinking Phase 2 alone suffices. Memory tip: “Phase 2 for the path, policy for the pass”—the selector opens the tunnel, but the firewall lets the traffic through.
NSE4 Authentication and VPN Practice Question
This NSE4 practice question tests your understanding of authentication and vpn. 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 needs to configure a hub-and-spoke IPsec VPN topology. Which TWO settings must be configured on the hub FortiGate to allow spokes to communicate with each other through the hub?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set Phase 2 selectors to 0.0.0.0/0 on the hub's side.
In hub-and-spoke, to allow spoke-to-spoke traffic via the hub, the hub must have Phase 2 selectors that cover the spoke subnets (0.0.0.0/0.0.0.0 or specific ranges) and the firewall policies must permit traffic between the spoke interfaces. Option B (Phase 2 with 0.0.0.0/0) allows any destination, and Option D (firewall policies allowing inter-spoke traffic) enables forwarding.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related NSE4 subnetting questions on CIDR, address ranges, and subnet selection.
Authentication and VPN — This question tests Authentication and VPN — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Set Phase 2 selectors to 0.0.0.0/0 on the hub's side. — In hub-and-spoke, to allow spoke-to-spoke traffic via the hub, the hub must have Phase 2 selectors that cover the spoke subnets (0.0.0.0/0.0.0.0 or specific ranges) and the firewall policies must permit traffic between the spoke interfaces. Option B (Phase 2 with 0.0.0.0/0) allows any destination, and Option D (firewall policies allowing inter-spoke traffic) enables forwarding.
What should I do if I get this NSE4 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related NSE4 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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. A FortiGate administrator has configured a hub-and-spoke IPsec VPN. The hub FortiGate has two Phase 2 selectors with spokes, but traffic between spokes is not routed via the hub. What must be configured on the hub to allow spoke-to-spoke communication?
hard
A.Set the hub as the default gateway on each spoke
B.Use policy-based VPN instead of route-based
C.Configure NAT on the hub
✓ D.Enable 'add-route' on the hub Phase 2
Why D: In hub-and-spoke, the hub needs Phase 2 selectors that cover the spoke subnets, and the spokes need static routes pointing to the hub for other spoke subnets. Additionally, enabling 'add-route' on the hub can help, but the key is proper Phase 2 configuration.
Last reviewed: Jun 21, 2026
Question Discussion
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This NSE4 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 NSE4 exam.
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