NSE4 Practice Test 14 — 15 Questions

Question 1

A FortiGate admin configures a firewall policy to allow outbound HTTP traffic and applies a web filter profile. The admin notices that some users can access a known malicious URL while others are blocked. All users are in the same source subnet (10.0.1.0/24). What is the MOST likely cause of this inconsistent behavior?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Some users have a different web filter profile applied due to a policy ordering issue where a higher-priority policy matches their traffic. When multiple firewall policies match traffic from the same source subnet, FortiGate uses the first matching policy in order (lowest policy ID). If a higher-priority policy with a different web filter profile matches some users' traffic (e.g., based on source port or application), those users will have different filtering behavior. This is a classic policy ordering issue where the intended web filter profile is not applied consistently to all users in the same subnet.

Answer

The FortiGate is using a proxy server that caches different results for different users

Answer

The web filter profile is configured to 'allow' but the FortiGuard rating is inconsistent

Answer

The firewall policy has an FQDN destination that resolves to different IPs for different users due to DNS load balancing

Question 2

An administrator receives reports that some internal users can access Facebook despite a web filtering profile that blocks the 'Social Networking' category. The policy is configured with deep inspection. Which THREE checks should the administrator perform to troubleshoot this issue?

Accepted Answer

Check if the users are using HTTPS and if the SSL inspection profile has an exemption for Facebook. The troubleshooting should focus on three main areas: (A) SSL inspection exemption – if users access Facebook via HTTPS and the SSL inspection profile exempts Facebook traffic, it bypasses the web filter; (C) SSL VPN bypass – traffic through an SSL VPN tunnel may not match the policy if the tunnel interface is not covered; (D) policy application and order – the web filtering profile must be applied to the correct policy and the policy order must be such that this policy is enforced before any conflicting policy. Option E is a valid check, but since the category is already set to 'Block' in the profile, the issue is more likely related to the other three.

Answer

Ensure that the antivirus profile is enabled on the policy

Answer

Confirm that the 'Social Networking' category is not set to 'Monitor' instead of 'Block'

Question 3

You run the command 'diagnose vpn ike log filter name vpn1' and then 'diagnose vpn ike log filter type phase1'. The log shows: 'IKEv1 exchange:f4470f07:00000000: responder: main mode: received IKE_SA_INIT (aggressive mode not allowed)'. What is the problem?

Accepted Answer

The responder is configured for main mode only, but the initiator is sending aggressive mode. The log message 'aggressive mode not allowed' indicates the responder (FortiGate) is configured to accept only main mode IKE phase1 negotiations, but the initiator sent an aggressive mode request. This mismatch causes the responder to reject the IKE_SA_INIT message, as aggressive mode is disabled by default or explicitly set to main mode only in the phase1 configuration.

Answer

The initiator is using IKEv2 while the responder uses IKEv1

Answer

The pre-shared key is wrong

Answer

The phase1 proposal is incompatible

Question 4

What is the purpose of configuring a loopback interface on a FortiGate?

Accepted Answer

To create a logical interface that remains up regardless of physical link status. A loopback interface is a logical interface that is not tied to any physical port, so it remains operational (up/up) as long as the FortiGate itself is running. This makes it ideal for management access, BGP peering, and other services that require a stable IP address independent of physical link failures.

Answer

To provide a virtual IP address for NAT

Answer

To connect to a VLAN

Answer

To aggregate multiple physical interfaces for increased bandwidth

Question 5

A network administrator notices that an IPS sensor is generating excessive false positives for a specific signature. The administrator wants to exclude traffic from a trusted internal server (IP 10.1.1.100) from inspection for that signature only, while keeping other signatures active. Which configuration change should the administrator apply?

Accepted Answer

Create an IPS filter that excludes the server's source IP address from the signature.. An IPS filter allows the administrator to define a rule that excludes traffic from a specific source IP address (10.1.1.100) from inspection for a particular signature, while leaving all other signatures active. This granular approach ensures that false positives for that signature are reduced without disabling the signature entirely or affecting other traffic.

Answer

Set the signature action to 'pass' and use an application control profile to bypass the server.

Answer

Disable the signature in the IPS sensor configuration.

Answer

Add the server's IP to the exempt list in the IPS sensor.

Question 6

A network admin configures a site-to-site IPsec VPN between two FortiGates using IKEv1 main mode. The tunnel establishes successfully, but no traffic passes. What is the MOST likely cause?

Accepted Answer

There is no firewall policy allowing traffic through the VPN tunnel. The tunnel establishes successfully, meaning IKE phase 1 and phase 2 negotiations completed correctly, which rules out mismatched proposals or incorrect pre-shared keys. However, even with a functional IPsec tunnel, traffic cannot flow unless a firewall policy explicitly permits it between the source and destination zones using the VPN interface. In FortiGate, the VPN tunnel is treated as an interface, and without a policy allowing traffic from the internal network to the VPN interface (or vice versa), packets are dropped by the firewall engine.

Answer

Aggressive mode should be used instead of main mode

Answer

The pre-shared key is incorrect

Answer

The phase2 proposal does not match between peers

Question 7

A FortiGate administrator is troubleshooting a problem where users cannot access the Internet. The FortiGate has a default route pointing to the ISP gateway. The administrator runs 'execute ping 8.8.8.8' from the FortiGate CLI and it succeeds. However, internal users behind NAT are unable to reach external servers. Which is the most likely cause?

Accepted Answer

No NAT policy is configured for internal users. The administrator confirmed that the FortiGate itself can reach the Internet (ping 8.8.8.8 succeeds), so the default route and basic connectivity are working. However, internal users behind NAT cannot reach external servers, which indicates that traffic from internal users is either not being translated or is being blocked. The most likely cause is that no NAT policy (or firewall policy with NAT enabled) exists to perform source NAT for internal users, so their private IP addresses are not translated to the FortiGate's public IP, and the ISP gateway drops the packets because private addresses are not routable on the Internet.

Answer

The default route is incorrectly configured

Answer

An implicit deny policy is blocking traffic from internal to external

Answer

External access profile is set to read-only

Question 8

An administrator configures a dial-up IPsec VPN using IKEv2 with certificates. Remote users can connect, but traffic is not routed through the tunnel. The Phase 1 status shows 'up', but Phase 2 shows 'down'. What is the most likely issue?

Accepted Answer

The Phase 2 proposals do not match between the FortiGate and the client.. In IKEv2 VPNs, Phase 1 establishes the secure control channel (ISAKMP SA) and shows 'up' even if Phase 2 fails. Phase 2 creates the IPsec SA for actual data traffic; if it remains 'down', the most common cause is a mismatch in Phase 2 proposals (encryption, authentication, or PFS settings) between the FortiGate and the remote client. Since the client can connect but traffic is not routed, the tunnel is not fully established for data, pointing directly to a Phase 2 proposal mismatch.

Answer

The firewall policy for the VPN traffic is missing.

Answer

The pre-shared key for Phase 2 is incorrect.

Answer

The remote user's client does not support IKEv2.

Question 9

A FortiGate administrator wants to ensure that traffic from the 192.168.1.0/24 network to the internet is translated to a single public IP address using overload (PAT). Which NAT configuration should be used?

Accepted Answer

Central SNAT with a dynamic IP pool using overload. Central SNAT with a dynamic IP pool using overload (PAT) is the correct method to translate all traffic from the 192.168.1.0/24 network to a single public IP address. The 'overload' option enables port address translation (PAT), allowing multiple internal hosts to share one public IP by using unique source port numbers, which is exactly what the administrator needs for internet-bound traffic.

Answer

Policy-based NAT with a fixed port range

Answer

One-to-one NAT IP Pool

Answer

Virtual IP (VIP) with port forwarding

Question 10

Which inspection mode in the antivirus profile processes traffic by buffering the entire file before scanning, allowing more thorough detection but potentially increasing latency?

Accepted Answer

Proxy-based inspection. Proxy-based inspection in the antivirus profile buffers the entire file in memory before scanning, enabling thorough detection of threats like polymorphic malware or embedded exploits. This mode reassembles the full data stream, allowing the FortiGate to perform deep content analysis, but it introduces higher latency due to the buffering and reassembly process.

Answer

Deep inspection

Answer

DNS inspection

Answer

Flow-based inspection

Question 11

A company with 500 employees uses FortiGate as their internet gateway. They recently enabled SSL deep inspection using the built-in CA certificate. After deployment, many users report that they cannot access their online banking websites. The error message in the browser says 'The certificate is not trusted'. The administrator has already pushed the FortiGate CA certificate to all domain-joined computers via Group Policy. However, the problem persists for banking sites. The administrator also notices that banking sites load fine on mobile devices that do not have the CA certificate installed. What is the most likely cause and solution?

Accepted Answer

Banking websites use certificate pinning. Exempt them from deep inspection using an SSL inspection exemption list.. Banking websites often use HTTP Public Key Pinning (HPKP) or certificate pinning, where the browser expects a specific certificate or public key from the server. When FortiGate performs SSL deep inspection, it re-signs the server's certificate with its own CA, breaking the pinning validation. This causes the 'certificate not trusted' error even when the FortiGate CA is trusted, because the browser detects that the presented certificate does not match the pinned certificate. The correct solution is to exempt banking sites from deep inspection using an SSL inspection exemption list, allowing the original server certificate to pass through.

Answer

Disable SSL inspection entirely to avoid certificate issues.

Answer

The CA certificate is not properly installed on all computers. Re-deploy via Group Policy.

Answer

Use certificate inspection instead of deep inspection for all traffic.

Question 12

A FortiGate is operating in transparent mode. The admin needs to allow HTTP traffic from users to a web server. Which type of firewall policy is required?

Accepted Answer

A layer 2 firewall policy. In transparent mode, the FortiGate operates as a Layer 2 bridge, forwarding traffic without routing. To allow HTTP traffic from users to a web server, a Layer 2 firewall policy is required because it filters traffic based on MAC addresses and Layer 2 headers, not IP addresses or routing decisions. This policy type is the only one that works in transparent mode, as it does not involve NAT or routing.

Answer

A policy-based NAT rule

Answer

A firewall policy using zone-based security

Answer

A VIP policy to map the web server's public IP

Question 13

You notice that the FortiGate HA cluster is not failing over when the primary unit loses power. The HA configuration shows 'set ha-priority 250' on the primary and 'set ha-priority 200' on the secondary. What is the most likely cause?

Accepted Answer

The HA heartbeat interface is not configured correctly or is down. The most likely cause is that the HA heartbeat interface is not configured correctly or is down (Option D). FortiGate HA relies on heartbeat packets exchanged over dedicated or VLAN interfaces to monitor peer status. If the heartbeat interface fails, the secondary unit cannot detect the primary's loss of power, so no failover occurs regardless of priority settings. The HA priority values (250 vs. 200) are valid and would normally cause the primary to be elected as the active unit, but a broken heartbeat link prevents failover detection.

Answer

The secondary unit has a lower priority, so it never takes over

Answer

The password for HA synchronization is incorrect

Answer

The session pickup feature is disabled

Question 14

An administrator has configured the policy shown in the exhibit. Traffic to the web server at 10.0.1.10 over HTTPS is allowed, but users complain that they cannot access the web server's login page. The IPS sensor 'High_Security_Sensor' has a signature that blocks SQL injection attempts. The application list 'Block_Social_Media' blocks Facebook and Twitter. What is the most likely cause of the issue?

Accepted Answer

The application control profile is blocking the web application.. The policy explicitly allows HTTPS traffic to 10.0.1.10, but the application control profile 'Block_Social_Media' is applied. This profile blocks Facebook and Twitter, which are web-based applications. If the web server's login page is served over HTTPS and is incorrectly classified by the FortiGate as a social media application (e.g., due to shared CDN or similar traffic patterns), the application control profile will block it, preventing user access despite the firewall policy allowing the service.

Answer

The IPS sensor is blocking the login page due to a false positive.

Answer

The firewall policy action is set to 'deny' but the exhibit shows 'accept'.

Answer

The HTTPS service is not correctly defined and blocking the traffic.

Question 15

An admin is configuring a policy-based NAT rule (central NAT) to translate internal users' source IPs to the external IP of the FortiGate interface. However, users complain that some applications fail. The admin notices that the NAT rule is using 'dynamic IP pool' with overload. What is the MOST likely cause of the application failures?

Accepted Answer

The applications are sensitive to NAT and require a fixed port range. Applications sensitive to NAT, such as SIP, H.323, or FTP, often require a fixed port range or an explicit NAT rule that preserves the original source port. When a dynamic IP pool with overload (PAT) is used, the FortiGate may change the source port, breaking protocols that embed IP addresses or port information in the payload. This is the most likely cause of application failures in this scenario.

Answer

The IP pool is exhausted and no more translations are available

Answer

The route to the destination is missing

Answer

The firewall policy does not have NAT enabled