Fortinet NSE7_FSN_AR-7.6 - Fortinet NSE 7 - Secure Networking 7.6 Architect

The correct answer is D. IKE_AUTH .

The study guide explicitly states:

“IKE_Auth exchange:

• Performs the mutual authentication of two IKE endpoints.

• Configures settings like IP/mask, DNS, and so on.

• Sets up the piggyback of a child SA. Negotiates IP flow and security settings for the IPsec SA.”

It also says:

“By default, a piggyback child (IPsec) SA is negotiated along with the IKEv2 SA during IKE_AUTH. If additional IPsec SAs are needed … they are negotiated during subsequent CREATE_CHILD_SA exchanges.”

Why the other options are wrong:

A. IKE_SA_INIT is incorrect because this exchange negotiates the security settings to protect the IKE traffic, not the first CHILD_SA.

B. INFORMATIONAL is incorrect because it is used to convey control messages between IKE endpoints.

C. CREATE_CHILD_SA is incorrect for the first CHILD_SA, because it is used to create new additional child SAs or rekey existing ones after the initial exchange.

The correct answer is C .

The exhibit shows:

562 in ESTABLISHED state

27 in CLOSE state

memory_tension_drop=0

ephemeral=0/131072

According to the study guide, for TCP sessions: “The protocol state in the session table is a two-digit number. For TCP, the first number (from left to right) is related to the server-side state and is 0 when the session is not subject to any inspection (flow or proxy)… The second digit is the client-side state.” The same page also shows that value 1 = ESTABLISHED

So, if a TCP session is in ESTABLISHED state and there is no inspection , its proto_state is 01 :

first digit 0 = no inspection

second digit 1 = ESTABLISHED

That makes C correct. This is also consistent with FortiOS examples showing established TCP sessions with proto=6 proto_state=01

Why the other options are wrong:

A is wrong because the field that indicates sessions dropped due to low free memory is memory_tension_drop, and in the exhibit it is 0 , not 113. The study guide states: “If there is a lack of free memory, the kernel deletes the oldest sessions. The command shown on this slide displays the number of sessions the kernel deleted because of this mechanism.” So 113 is the clash value, not memory-tension drops.

B is wrong because ephemeral=0/131072 does not mean 131072 ephemeral sessions were recorded. The study guide explains that FortiGate “sets a hard limit on the maximum number of ephemeral sessions that can exist at the same time in the session table.” Therefore:

0 = current ephemeral sessions

131072 = maximum allowed ephemeral sessions for that model/context

D is wrong because the study guide says the temporary retention for possible out-of-order packets happens in state value 5 (TIME_WAIT) : “When a session is closed by both the sender and receiver, FortiGate keeps that session in the session table for a few seconds, to allow for any out-of-order packets that might arrive after the FIN/ACK packet. This is the state value 5.” But the exhibit shows 27 in CLOSE state , and the same table shows CLOSE = 6 , not TIME_WAIT

So the verified answer is C .

The output of the diagnose sys session list command provides the critical evidence needed to determine the behavior during a failover:

Session Synchronization (synced):

The most important indicator in the exhibit is the synced flag located in the state= line (state=may_dirty synced none app_ntf).

In FortiOS HA (High Availability), the synced flag confirms that this specific session has been successfully synchronized from the primary device to the secondary (backup) device.

Session synchronization (Session Pickup) ensures that if the primary unit fails, the secondary unit already has the session in its table and can resume traffic processing immediately.

TCP State (proto_state=01):

The output shows proto=6 (TCP) and proto_state=01.

In the FortiGate session table, proto_state=01 for TCP indicates that the session is in the ESTABLISHED state (post-three-way handshake).

This invalidates Option B, which claims the TCP session is not fully established.

Failover Outcome:

Because the session is ESTABLISHED and SYNCED, the secondary device will seamlessly take over the session upon primary failure.

The traffic continues to flow through the new primary without requiring the user/client to restart the connection. This is the primary function of HA Session Pickup.

Why other options are incorrect:

A: While the output shows app_ntf (Application Control notification) and may_dirty, the presence of the synced flag overrides this concern regarding failover. If the session type were not supported for failover (e.g., certain proxy sessions in older versions), it would not be marked as synced. Since it is synced, it persists.

B: As noted, proto_state=01 means established, not " not fully established " .

D: While the kernel updates routing tables, the purpose of syncing the session is to preserve the state so it does not need to be re-evaluated as a new packet would, preventing traffic drops.

The correct answers are A, D, and E . This is a feasible path RPF check scenario. In FortiGate’s default RPF behavior, FortiGate checks whether the routing table contains a valid return route to the source IP address through the same interface on which the packet arrived . The study guide’s RPF feasible path example states that FortiGate “checks the routing table for a route that matches the source address and incoming interface of the first original packet.” It then gives the exact result: User A passes because “there is a default route through wan1,” so packets received on wan1 pass the RPF check regardless of source address. User B fails because FortiGate does not have a route to 95.56.234.24 through wan2 . User C fails because FortiGate does not have a route to 10.0.4.63 through port1 . Therefore, option B is wrong because FortiGate is not allowing asymmetric return routing here. Option C is wrong because the default route points out wan1 , not port1 , so it cannot validate User C’s packet arriving on port1.

Intermittent behavior (working sometimes, failing others) points to resource or connectivity fluctuations rather than static misconfigurations.

B. Check that FortiGate is not entering conserve mode:

Reason: When FortiGate enters Conserve Mode (due to high memory usage), it changes its inspection behavior to save resources. Depending on the av-failopen setting, it may either bypass inspection (allowing blocked sites) or drop traffic (blocking valid sites) temporarily until memory recovers. This flapping between states causes intermittent filtering issues.

D. Check that the communication between FortiGate and FortiGuard is stable:

Reason: The Web Filter engine relies on real-time queries to the FortiGuard Distribution Network (FDN) to categorize URLs that are not in the local cache. If the internet connection or the specific path to FortiGuard is unstable (packet loss, latency), queries will time out. This results in " Rating Errors, " which can block or allow traffic unpredictably based on the " Allow websites when a rating error occurs " setting.

Why other options are incorrect:

A: A mismatch in inspection mode (e.g., Profile set to Proxy, Policy set to Flow) is a static configuration error. It would typically result in the profile not being selectable or consistently failing/not applying, rather than working intermittently.

C: If the wrong port is mapped (e.g., HTTP on 8080 is not mapped), the inspection engine will consistently ignore traffic on that port. It would not be intermittent.

The correct answer is A .

The study guide explains the IKEv2 exchange order very clearly:

“The initial exchanges are: IKE_SA_INIT and IKE_AUTH.”

“Create_Child_SA exchange: Creates a new child SA or rekeys an existing child SA.”

It also states:

“After successful IKE_SA_INIT and IKE_AUTH exchanges, the CHILD_SA exchange takes place. In this exchange, the peers negotiate the CHILD_SA and the traffic selectors — traffic selector responder (TSr) and traffic selector initiator (TSi).”

That is why A is correct: if the tunnel was initially brought up successfully , then the initial exchanges already succeeded. A later problem during CREATE_CHILD_SA , especially with traffic selectors/phase 2 selectors , can cause the tunnel to fail during rekey or child-SA renegotiation.

Why the other options are wrong:

B is wrong because proposal mismatch for the IKE SA is handled during IKE_SA_INIT , not after the tunnel is already up. The study guide says IKE_SA_INIT negotiates the security settings to protect the IKE traffic

C is wrong because a pre-shared key mismatch is part of authentication and would prevent successful initial establishment during IKE_AUTH . The study guide shows that after IKE_AUTH, “authentication succeeded” and “established IKE SA” when it works

D is wrong because a Diffie-Hellman mismatch belongs to IKE_SA_INIT , which happens before the tunnel comes up. The study guide also states: “By IKEv2 design, no Diffie-Hellman public key is exchanged during an IKE_AUTH exchange.”

So the verified answer is: A .

The correct answers are A and C .

The exhibit shows that preserve-session-route is enabled on port1:

config system interface

edit " port1 "

set preserve-session-route enable

next

end

The study guide explains the effect of this setting exactly:

“enable: FortiGate marks existing session routing information as persistent, and applies only the modified routes to new sessions”

It also states:

“The current route must still be present in the FIB. Otherwise, FortiGate flags the session as dirty and reevaluates it”

And the same page further clarifies:

“If you enable this setting, sessions passing through that interface continue to pass without being affected by the routing changes. The routing changes apply only to new sessions. If the route is removed from the FIB, then FortiGate must flag the session as dirty, flush its gateway information, and reevaluate the session.”

This proves:

A is correct because with preserve-session-route enable, existing sessions are normally preserved and routing changes apply only to new sessions.

C is correct because the session remains unchanged unless the current route is removed from the FIB/routing table, in which case FortiGate dirties and reevaluates the session.

Why the other options are wrong:

B is wrong because when the active route is removed, FortiGate does not simply mark the session dirty and stop there. The study guide says it “flags the session as dirty and reevaluates it” , which means route lookup happens again.

D is wrong because the session does change if the active route is removed. FortiGate flushes gateway information and reevaluates the session.

So the verified answers are: A, C .