The Fortinet NSE 6 - Network Security 7.6 Support Engineer (FCSS_NST_SE-7.6)

The correct answers are A and D .

The debug output shows:

Sent RADIUS req to server ' RadiusServer ' : IP=172.25.188.164 ... user= " student " using CHAP

Result for radius svr ' RadiusServer ' 172.25.188.164(0) is 0

Sending result 0 for req 2

The study guide explains that in RADIUS real-time debug, FortiGate shows the IP address of the RADIUS server it is querying. In the example, it says FortiGate “creates an access request to the RADIUS server at IP address 10.0.13.130” and shows the line Sent radius req to server ... IP=10.0.13.130

So in your exhibit, the queried server is clearly 172.25.188.164 , which makes A correct.

The study guide also states:

“The message fnbamd_comm_send_result-Sending result 0 indicates that the authentication was successful and that FortiGate received the Access-Accept message.”

Since your exhibit also ends with Sending result 0 , that makes D correct.

Why the other options are wrong:

B is wrong because result 0 means authentication successful , not failed

C is wrong because the debug explicitly shows using CHAP , and the study guide lists supported RADIUS schemes as CHAP, PAP, MS-CHAP, and MS-CHAPv2

E is wrong because the study guide says two-factor authentication would involve an Access-Challenge response: “If two-factor authentication is enabled on the server, the response is an Access-Challenge message” Your exhibit shows successful result 0 / Access-Accept , not a challenge.

So the verified answers are: A, D .

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 D .

The exhibit shows:

session_count=591

clash=162

memory_tension_drop=0

TCP sessions:

166 in NONE state

1 in ESTABLISHED state

3 in SYN_SENT state

2 in TIME_WAIT state

The study guide explains the TCP protocol states and states explicitly:

“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.”

In diagnose sys session stat, the exhibit shows 2 in TIME_WAIT state . Since TIME_WAIT = state value 5 , those are the sessions being kept briefly for possible out-of-order packets. That makes D correct.

Why the other options are wrong:

A is wrong because session_count=591 is the total number of sessions, while the TCP sessions shown add up to only 172 (166 + 1 + 3 + 2). So not all sessions in the table are TCP sessions.

B is wrong because the study guide says the number of sessions deleted because of low free memory is shown by memory_tension_drop , and in the exhibit it is 0 , not 162.

C is wrong because the study guide defines ephemeral/open TCP sessions as those not fully established , but the exhibit does not say all 166 in NONE state are specifically “waiting to complete the three-way handshake.” The clearest directly supported statement from the displayed states is the 2 TIME_WAIT sessions retained for out-of-order packets.

So the verified answer is: D .

Parallel Path Processing (PPP) in FortiOS refers to the system’s ability to evaluate and select among multiple processing paths—often involving dedicated network processors, content processors, or CPU-based workflows—to optimally process packets. The official documentation highlights that the PPP engine dynamically selects which hardware or software path to use for each session based on session characteristics, policy configuration, and traffic type. This dynamic selection results in optimal throughput and resource utilization.

The document specifies that PPP assesses several processing paths in parallel, using decision logic to determine whether a session should be offloaded to specialist hardware (like NP6, CP9, etc.) or stay in the CPU path, ensuring that each packet is handled by the most efficient available method under current load and policy. Hardware and software configurations both influence this outcome, but it is the PPP engine ' s decision-making that defines the optimal path per session.

To determine the type of policy route, we must interpret the specific flags and fields visible in the diagnose firewall proute list (or similar kernel table) output provided in the exhibit

Identify Key Indicators:

The most critical field in the output is vwl_service=1(test123).

It also lists vwl_mbr_seq=1 5.

Decode the Terminology:

vwl: This stands for Virtual WAN Link. In FortiOS, " Virtual WAN Link " is the legacy internal name for the SD-WAN feature. Even in newer firmware versions (7.x), the kernel and CLI debugs often still refer to SD-WAN objects as vwl.

vwl_service: This specifically refers to an SD-WAN Rule (also known as an SD-WAN Service). The name (test123) is the name given to that specific SD-WAN rule by the administrator.

Evaluate the Options:

A & D (Regular Policy Route): Standard policy routes (configured under config router policy) do not carry the vwl_service tag. They are typically identified by simple gateway or interface instructions without the SD-WAN service abstraction.

B (ISDB Route): While SD-WAN rules can use the Internet Service Database (ISDB) as a destination, the structure of the route entry shown here—specifically defined by a vwl_service ID—classifies it fundamentally as an SD-WAN rule, regardless of the destination object.

C (An SD-WAN rule): The presence of vwl_service and vwl_mbr_seq (SD-WAN member sequence) definitively identifies this entry as a rule generated by the SD-WAN subsystem.

Conclusion: The output shows a route controlled by the SD-WAN engine (vwl), confirming it is an SD-WAN rule.

The exhibit shows:

memory conserve mode: on

memory used: 2706 MB 89% of total RAM

memory used threshold red: 2675 MB 88% of total RAM

memory used + freeable threshold extreme: 2887 MB 95% of total RAM

The study guide states that the default thresholds are:

Extreme = 95%

Red = 88%

Green = 82%

So this FortiGate is in conserve mode because memory usage is 89% , which is above the red threshold (88%) , but it has not yet reached the extreme threshold (95%) .

The study guide then explains exactly what happens during conserve mode:

“For traffic that requires proxy-based inspection (and if memory usage has not exceeded the extreme threshold):

config system global

set av-failopen [off | pass | one-shot]

pass (default): All new sessions pass without inspection”

It also says:

“The av-failopen setting also applies to flow-based antivirus inspection.”

And the same page adds:

“If memory usage exceeds the extreme threshold, all new sessions that require inspection (flow-based or proxy-based) are blocked.”

Therefore, with default settings and with memory usage below the extreme threshold , FortiGate is allowing new sessions that require inspection, but bypassing inspection . That matches C .

Why the other options are wrong:

A is wrong because the default behavior is not to block proxy-based inspected sessions; the default is pass , meaning they pass without inspection

B is wrong because if memory rises another 6% , it reaches 95% , which is the extreme threshold . At that point, the study guide says all new sessions that require inspection are blocked

D is wrong because FortiGate blocks all new inspected sessions only when memory usage exceeds the extreme threshold , and the exhibit shows it is currently at 89% , not 95%

The key point is that the two VPNs are dynamic dialup IPsec tunnels on the same interface and both are using IKEv1 main mode . In this design, FortiGate cannot reliably distinguish which dialup phase1 to match before phase 1 completes.

The uploaded Network Security Support Engineer 7.6 Study Guide shows that XAuth happens only after phase 1 is already established:

“The IKE real-time debug shows, after phase 1, the exchange of extended authentication (XAuth) packets… You can also see the CFG_REPLY, showing the XAuth user and group name.”

That means the user group is learned too late to be used for selecting the correct phase1 definition. So the fix must be applied to the phase1 matching method itself , not to XAuth.

The FortiOS administration guide gives the exact rule for this scenario:

“When the remote VPN peer has a dynamic IP address and is authenticated by a pre-shared key you must select Aggressive mode if there is more than one dialup phase 1 configuration for the interface IP address.”

The debug flow message iprope_in_check() check failed, drop specifically indicates a failure in the Local-In Policy check. The " iprope " (IP ROouting Policy Enforcement) engine handles policy lookups. The _in_check suffix confirms that the decision is regarding traffic destined to the FortiGate itself (Local-In traffic), rather than traffic passing through it.

D. The packet was dropped because the requested service is not enabled on FortiGate:

This is the most common cause. When a packet arrives destined for the FortiGate ' s interface IP (e.g., an HTTPS or SSH request), the kernel checks if that specific service is enabled in the interface settings (set allowaccess). If the service is not enabled (e.g., trying to Ping an interface where PING access is disabled), the iprope_in_check function fails and drops the packet immediately.

C. The packet was dropped because the trusted host list is misconfigured:

Even if the service (e.g., HTTPS) is enabled on the interface, the FortiGate checks the Administrator settings. If Trusted Hosts are configured, the source IP of the incoming packet is compared against the allowed list. If the IP is not on the list, the Local-In policy check (iprope_in_check) fails, and the packet is dropped to secure the management plane.

Why other options are incorrect:

A: If traffic is dropped by a standard Firewall Policy (traffic passing through the device from one interface to another), the debug message will typically state denied by policy x or no matching policy. It would generally be a forward check (iprope_fwd_check or similar), not an _in_check.

B: If there is no route to the source, the error is a Reverse Path Forwarding (RPF) failure. The debug flow logs this explicitly as reverse path check fail, drop.