NSE4_FGT_AD-7.6 Fortinet NSE 4 - FortiOS 7.6 Administrator Questions and Answers

Phase 1 being up confirms the two FortiGate devices can authenticate and build the IKE SA. Phase 2 failing indicates the IPsec (Quick Mode) SA negotiation is failing due to mismatched Phase 2 parameters.

From the exhibit, the Phase 2 mismatches that would prevent SA establishment are:

1) Phase 2 selectors must mirror each other (Proxy IDs)

HQ-NGFW Phase 2 selector shows:

Local: 10.0.11.0/24

Remote: 172.20.1.0/24

BR1-FGT Phase 2 selector shows:

Local: 172.20.1.0/24

Remote: 10.11.0.0/24 ⟵ does not match HQ’s local subnet (10.0.11.0/24)

In FortiOS, Phase 2 comes up only when the peers’ selectors (proxy IDs) match as opposite pairs (local on one side = remote on the other).

✅ Fix: A. On BR1-FGT, set Remote Address to 10.0.11.0/255.255.255.0.

2) Phase 2 proposal must match (encryption/authentication)

HQ-NGFW shows encryption AES128 (with SHA1)

BR1-FGT shows encryption AES256 (with SHA1)

For Phase 2 to establish, both peers must have at least one common proposal (same encryption and authentication settings). With one side set to AES128 and the other to AES256, there is no match.

✅ Fix: D. On HQ-NGFW, set Encryption to AES256.

Why the other options are not correct

B. Enable Diffie-Hellman Group 2: The exhibit’s mismatch is not resolved by adding DH group 2, and DH group must match when PFS is enabled. This option does not align the peers based on what’s shown.

C. Set Seconds to 43200: Phase 2 lifetime mismatches typically do not prevent Phase 2 from coming up (the negotiated lifetime can be adjusted by the peers). The hard blockers here are the selectors and proposal mismatch.

From the routing table in the exhibit, there is already a static route for 172.20.1.0/24 pointing out port3 with:

Distance = 9

Priority = 2

Type = Static

In FortiOS, route selection prefers (in order) the route with the lowest administrative distance to a destination. Therefore, to make traffic to 172.20.1.0/24 go through port2 only, the administrator must ensure the port2 static route is more preferred than the existing port3 route.

Why C is correct

C. The existing static route through port3 must have the distance set to 11.

If the existing port3 route distance is increased to 11, then a new port2 route with distance 9 will be preferred (9 < 11). This makes the port3 route a backup route instead of the active one.

Why D is correct

D. The new static route must have the distance set to 9

Setting the new port2 route distance to 9 (and increasing the port3 route to 11 as in option C) ensures FortiGate selects the port2 route as the best route for 172.20.1.0/24.

Why A and B are not correct

A (priority 3): By itself it does not guarantee selection over the existing route, and FortiOS route choice is driven primarily by distance.

B (metric 1): Metric is not the primary selector for static route preference compared to administrative distance in this scenario.

So the two criteria that achieve the objective are:

Make the existing port3 route less preferred by increasing its distance (C)

Ensure the new port2 route uses the preferred distance (D)

From the exhibits, there are three relevant firewall policies from LAN (port4) to WAN (port2), each using a different IP pool for source NAT:

TCP traffic

Service: ALL_TCP

Destination: BR1-FGT

IP Pool: SNAT-Pool → 100.65.0.49

PING traffic

Service: PING

Destination: all

IP Pool: SNAT-Remote1 → 100.65.0.99

IGMP traffic

Service: IGMP

Destination: all

IP Pool: SNAT-Remote → 100.65.0.149

The user on HQ-PC-1 (10.0.11.50) is pinging BR1-FGT (100.65.1.111). In FortiOS, policy matching is based on (among other fields) source, destination, and service, and the first matching policy in top-down order is applied.

Because the traffic is ICMP echo (ping), it matches the policy named PING traffic (service PING, destination all). That policy explicitly uses Use Dynamic IP Pool with SNAT-Remote1, which is configured with external IP 100.65.0.99.

Therefore, the source NAT IP used for this ping is 100.65.0.99.

According to the FortiOS 7.6 Administration Guide and Fortinet hardware acceleration (NTurbo) documentation, the correct answer is A.

What NTurbo Is (FortiOS 7.6 – Verified)

NTurbo is a hardware-based acceleration feature available on specific FortiGate models. It is designed to improve antivirus and IPS performance when operating in flow-based inspection mode.

NTurbo works by creating a fast, optimized data path between:

FortiGate ingress interface

IPS/AV engine

FortiGate egress interface

This minimizes CPU involvement and reduces packet traversal overhead.

Why Option A Is Correct

A. For flow-based inspection, NTurbo establishes a dedicated data path to redirect traffic between the IPS engine and FortiGate ingress and egress interfaces.

This is exactly how NTurbo works, as documented:

NTurbo applies to flow-based inspection only

It accelerates IPS and antivirus scanning

It creates a dedicated fast path that bypasses unnecessary processing steps

This significantly improves throughput and lowers latency

This description matches Fortinet’s official explanation of NTurbo.

Why the Other Options Are Incorrect

B. NTurbo creates two inspection sessions

Incorrect. NTurbo does not duplicate sessions; it optimizes the packet path.

C. NTurbo offloads traffic to the content processor (proxy-based)

Incorrect. NTurbo does not apply to proxy-based inspection and does not offload to content processors.

D. NTurbo buffers the whole file and then sends it to the antivirus engine

Incorrect. Buffering entire files is a proxy-based behavior, not NTurbo.

In FortiOS 7.6, web filter profiles are inspection-mode dependent. Certain advanced web filtering features—such as daily category usage quota—are only supported when the firewall policy is operating in proxy-based inspection mode.

Why the profile is not visible

The profile restrictmedia-profile includes a daily category usage quota.

Daily quotas are a proxy-based web filtering feature.

If the firewall policy is configured with:

Inspection mode: Flow-based

Then FortiGate will not display proxy-only web filter profiles in the Web Filter drop-down list.

FortiGate automatically filters the available profiles based on feature compatibility with the policy’s inspection mode.

This behavior is explicitly documented in the FortiOS 7.6 Web Filtering and Inspection Mode Compatibility sections.

Why the other options are incorrect

A. Already referenced in another firewall policyWeb filter profiles can be reused across multiple policies. This does not hide them.

B. Firewall policy is in no-inspection mode instead of deep-inspectionSSL inspection depth affects HTTPS visibility, not whether a web filter profile appears in the drop-down list.

C. Naming convention restrictionFortiOS does not restrict profile selection based on naming conventions.

In FortiOS 7.6, when multiple dialup IPsec VPNs are configured on the same FortiGate—especially in Aggressive Mode—FortiGate must identify which Phase 1 configuration a connecting client should match.

How FortiGate selects a dialup IPsec tunnel

For dialup VPNs:

The remote peer (user or device) does not have a fixed IP address

Multiple Phase 1 interfaces may exist on the HQ FortiGate

FortiGate uses identifying information sent during IKE Phase 1 to select the correct tunnel

Aggressive Mode behavior

Aggressive mode sends ID information in clear text during Phase 1

This allows FortiGate to match incoming peers to the correct Phase 1 configuration

Why Peer ID is the correct answer

C. Peer ID

Peer ID (also called IKE ID) is used to:

Identify the remote peer

Differentiate between multiple dialup tunnels

Common Peer ID formats:

FQDN

User FQDN

Key ID

FortiGate matches the received Peer ID against the Phase 1 configuration to select the correct tunnel

This is the documented and recommended method for:

Mapping users to different department tunnels

Supporting multiple dialup IPsec VPNs in aggressive mode

Why the other options are incorrect

A. Local GatewayIdentifies the local FortiGate interface/IP, not the remote user.

B. Dead Peer DetectionUsed only for tunnel health monitoring, not tunnel selection.

D. IKE Mode ConfigUsed for assigning IP addresses and pushing settings, not for selecting the Phase 1 tunnel.

In FortiOS 7.6, HA cluster heartbeat IP addresses are automatically managed by FortiGate and play a critical role in cluster communication and synchronization.

Correct statements

A. Heartbeat IP addresses are used to distinguish between cluster members.

Correct

FortiGate assigns unique heartbeat IP addresses (link-local addresses in the 169.254.0.0/16 range) to each HA member.

These addresses are used for:

Cluster member identification

Health checks

Synchronization traffic

This allows FortiGate units to uniquely identify and communicate with each other inside the HA cluster.

C. A change in the heartbeat IP address happens when a FortiGate device joins or leaves the cluster.

Correct

Heartbeat IPs are dynamically assigned.

When:

A new FortiGate joins the cluster, or

A member leaves or fails,

FortiGate may reassign heartbeat IP addresses to maintain unique identification among members.

This behavior is documented in the FortiOS HA operation and troubleshooting guides.

Why the other options are incorrect

B. The heartbeat interface of the primary device is always assigned IP address 169.254.0.1.

Incorrect

There is no fixed or guaranteed heartbeat IP (such as 169.254.0.1) for the primary unit.

Heartbeat IP assignment is dynamic, not role-based.

D. Heartbeat interfaces have virtual IP addresses that are manually assigned.

Incorrect

Heartbeat IP addresses are:

Automatically assigned

Link-local

Administrators do not manually configure heartbeat IP addresses.

In FortiOS 7.6, SD-WAN steering decisions are recorded in traffic logs only when traffic matches an explicit SD-WAN rule (SD-WAN service rule). When no configured SD-WAN rule matches a session, FortiGate uses the implicit (default) SD-WAN rule/behavior to select a member (often resulting in load-balancing or default selection based on the configured SD-WAN algorithm).

In the exhibit, traffic is permitted by firewall policy ID 1, and the Destination Interface alternates between port1 and port2, but SD-WAN Rule Name remains empty. This is consistent with the sessions being forwarded by the implicit SD-WAN rule, which does not populate a named rule in the log columns.

Why the other options are not correct:

A: SD-WAN rule name logging is not a “delayed display” behavior requiring refresh; it is populated per-session when an explicit rule matches.

B: Application Control is not required for SD-WAN rule name to appear. Rule name logging depends on SD-WAN rule match, not on whether Application Control is enabled.

C: Feature visibility affects GUI display options, but the exhibit already shows the SD-WAN columns enabled; the issue is that no explicit SD-WAN rule is being hit.

Based on the exhibit and FortiOS 7.6 Active Authentication (captive portal) behavior, the most likely reason the user is not presented with a login prompt is that DNS is missing from the firewall policy.

What the exhibit shows

The firewall policy configured for active authentication includes:

Source: HQ_SUBNET and Remote-users

Destination: all

Services:

HTTP

HTTPS

ALL_ICMP

Security Profiles: Web filter and SSL inspection enabled

Authentication: Active (user group referenced)

DNS is not included as a service in the policy.

Why DNS is required for active authentication

In FortiOS 7.6, active authentication (captive portal) works as follows:

The user attempts to access a website using a URL (for example, www.example.com).

The client must first perform a DNS lookup to resolve the domain name.

FortiGate intercepts the initial HTTP/HTTPS request and redirects the user to the authentication portal.

If DNS traffic is blocked or not allowed:

The hostname cannot be resolved.

The HTTP/HTTPS request never properly occurs.

FortiGate has nothing to intercept, so the login prompt is never triggered.

This is explicitly documented in the FortiOS 7.6 Authentication and Captive Portal requirements, which state that DNS must be permitted for captive portal–based authentication to function correctly.

Why the other options are incorrect

A. No matching user account exists for this user

Incorrect.

If the user account did not exist, the login page would still appear, but authentication would fail after credentials are entered.

B. The Remote-users group must be set up correctly in the FSSO configuration

Incorrect.

This policy is using active authentication, not FSSO.

FSSO configuration is irrelevant for active authentication login prompts.

C. The Remote-users group is not added to the Destination

Incorrect.

User groups are applied in the Source field for authentication-based policies.

Destination does not accept user groups.

From the HA configuration shown for HQ-NGFW-1:

set memory-based-failover enable

set memory-failover-threshold 70

set memory-failover-monitor-period 50

set memory-failover-sample-rate 10

set memory-failover-flip-timeout 60

set override disable

set priority 200

From the performance status outputs:

HQ-NGFW-1 memory used is 90% (well above the configured threshold of 70%)

HQ-NGFW-2 memory used is about 48.7% (well below the threshold)

What happens in FortiOS 7.6 with memory-based failover

When memory-based failover is enabled, FortiGate monitors memory utilization. If the unit’s memory usage stays above the configured memory-failover-threshold for the configured memory-failover-monitor-period, the cluster triggers a failover away from the unit under memory pressure.

Threshold = 70%

HQ-NGFW-1 is at 90%, so it violates the threshold.

Monitor period = 50 seconds.

The administrator observed for 55 seconds, which is longer than 50 seconds, so the condition is met for long enough to trigger failover.

The memory-failover-flip-timeout 60 is used to prevent rapid back-and-forth role changes (flapping) after a failover decision; it does not prevent the initial failover from occurring once the threshold breach persists for the monitor period.