Quick Answer
The answer is to check the routing table for routes pointing to the remote networks and verify that firewall policies permit the traffic. This is correct because an IPsec VPN tunnel being established only confirms that the IKE and IPsec security associations are up, but it does not automatically route or allow data to pass; traffic must have a valid route in the routing table directing it to the tunnel interface, and a firewall policy must explicitly match the source, destination, and service to forward that traffic through the tunnel. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your understanding that a Phase 2 tunnel status is independent of traffic flow, a common trap where candidates assume a green tunnel means connectivity is working. A key memory tip is “Tunnel up does not mean traffic through”—always check routes and policies first when troubleshooting an IPsec VPN with no traffic.
This NSE4 practice question tests your understanding of authentication and vpn. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A site-to-site IPsec VPN is configured with IKEv2. The tunnel establishes but traffic does not pass. Which two troubleshooting steps should the administrator perform first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Check the Phase 2 selectors.
Why wrong: Phase 2 is up.
Verify that the Phase 1 proposal matches.
Why wrong: Phase 1 is already up.
Check the firewall policies allowing traffic through the tunnel.
Policies must permit traffic between zones.
Check the routing table for routes pointing to the remote networks.
Proper routes are needed for traffic to use tunnel.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Check the firewall policies allowing traffic through the tunnel.
Option C is correct because even if the IPsec tunnel is established, traffic will not pass unless firewall policies explicitly permit it. In FortiGate, a Phase 2 tunnel being up does not imply that traffic is allowed; you must have a policy that matches the source/destination and enables the action to forward traffic through the tunnel interface.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Check the Phase 2 selectors.
Why it's wrong here
Phase 2 is up.
Verify that the Phase 1 proposal matches.
Why it's wrong here
Phase 1 is already up.
Check the firewall policies allowing traffic through the tunnel.
Why this is correct
Policies must permit traffic between zones.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Check the routing table for routes pointing to the remote networks.
Why this is correct
Proper routes are needed for traffic to use tunnel.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates assume a 'tunnel up' status guarantees traffic flow, but FortiGate separates tunnel negotiation from firewall policy enforcement, so both a policy and a route are required for traffic to pass.
Detailed technical explanation
In FortiGate, IPsec tunnel establishment (Phase 1 and Phase 2) only creates the security associations (SAs). Traffic forwarding requires a firewall policy that references the tunnel interface and has the correct source/destination addresses and action set to ACCEPT. Additionally, a static route pointing to the remote network via the tunnel interface is necessary for the FortiGate to know where to send the traffic.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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Authentication and VPN — study guide chapter
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FAQ
Authentication and VPN — This question tests Authentication and VPN — Read the scenario before looking for a memorised answer..
The correct answer is: Check the firewall policies allowing traffic through the tunnel. — Option C is correct because even if the IPsec tunnel is established, traffic will not pass unless firewall policies explicitly permit it. In FortiGate, a Phase 2 tunnel being up does not imply that traffic is allowed; you must have a policy that matches the source/destination and enables the action to forward traffic through the tunnel interface.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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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