FCSS_NST_SE-7.6 Questions and Answers

The correct answer is A. This behavior is dictated by the configuration command set snat-route-change enable shown in Exhibit 1 under config system global.

Routing Change: By changing the priority of route ID 2 from 10 to 0, it becomes lower than route ID 1 (priority 5). In FortiOS, a lower priority value indicates a more preferred route. Consequently, the active route for the destination changes from port1 to port2.

SNAT Implication: The existing session (shown in Exhibit 2) is using Source NAT (SNAT) with the IP address associated with port1 (10.200.1.1). If the traffic were simply switched to port2, the source IP would be incorrect for that interface and the return traffic would likely fail or be dropped.

snat-route-change enable: This specific setting instructs the FortiGate on how to handle established SNAT sessions when a routing change occurs that alters the preferred outgoing interface. When enabled, if a route change forces an SNAT session to a new interface, FortiGate flushes (deletes) the session from the session table. This is necessary because a live TCP session cannot survive a change in its source IP address. The client must initiate a new session, which will then be created using the new correct route (port2) and the corresponding new SNAT IP.

If this setting were disabled, the session would likely remain "sticky" to the original interface (port1) until it closed, provided the route still existed. However, the explicit configuration forces the deletion.

The exhibit shows a FortiGate configuration under config system fortiguard related to web filtering and FortiGuard options. There is a line:

set webfilter-force-off enable

According to official Fortinet documentation, the "webfilter-force-off" option, when enabled, causes the FortiGate to bypass web filtering for all traffic—even if a web filter profile is applied to a policy. This override is typically used for troubleshooting or performance reasons and is documented as an explicit bypass feature.

If an administrator wants to enforce web filtering inspection, this setting must be disabled. The correct way to restore web filtering functionality is to run:

set webfilter-force-off disable

Once done, traffic passing through policies with web filter profiles will be inspected and filtered as per configuration. Other settings such as timeout or cache TTL do not bypass web filtering; they only affect operational nuances.

The partial output from diagnose hardware sysinfo memory provides details on system RAM allocation. According to Fortinet's technical documentation for memory troubleshooting and Linux memory management (which FortiOS is based on):

MemFree is the portion of physical memory not currently allocated to any running process or kernel function. Thus, 708880 kB is available and can be immediately used by user-space programs or system operations.

Inactive refers to pages in the memory cache that were previously in use for I/O or file system buffering but are now not actively referenced. These pages are retained in memory for quick access if needed again, but can be reclaimed for other memory operations if demand increases. The value 98908 kB here represents currently unused cache pages (inactive pages), ready for repurposing or deletion if the system requires more RAM.

Cached represents the total amount of system memory allocated to cache, which includes both active and inactive cache pages. It does not, by itself, represent I/O cache exclusively, nor does "inactive" mean memory “will never be used” as the kernel can re-purpose inactive pages on demand.

The diagnose debug authd fsso server command is the primary tool for troubleshooting communication between the FortiGate and the FSSO Collector Agent. This debug output reveals the status of the connection and the reasons for failure. The three most common connectivity issues identified by this debug are:

FortiGate cannot reach the IP address of the collector agent (Option C): The debug will show connection timeouts or "host unreachable" errors if the Layer 3 connectivity is missing.

The connection was refused / Port mismatch (Option B): If the FortiGate can reach the IP but the Collector Agent is not listening on the specified port (default 8000), the debug will display "Connection refused." This often happens if the port configured on the FortiGate does not match the listening port on the agent.

The pre-shared key does not match (Option D): If the IP and Port are correct, the next step is authentication. If the password configured on the FortiGate does not match the one on the Collector Agent, the debug will explicitly show an "Authentication failed" or "password mismatch" error during the handshake.

Note on other options: Option A (SSL) is less common than basic connectivity/auth mismatches. Option E (Group filters) relates to user processing logic, which occurs after connectivity is established.

The administrator cannot see traffic in the sniffer because it is being offloaded to the NPU (NP6). To view the traffic, offloading must be disabled so packets pass through the CPU.

B. config firewall policy ... set auto-asic-offload disable: This is the recommended method to troubleshoot specific traffic. By disabling ASIC offloading in the relevant firewall policies (Policies 5 and 17 in the exhibit), traffic is forced to the CPU and becomes visible to the sniffer.

C. diagnose npu np6 fastpath disable 1: This command temporarily disables the fastpath processing on the specific NP6 processor (ID 1) handling the ports. This forces all traffic handled by that NPU to the CPU, allowing the sniffer to capture it.

Incorrect Options: Option A uses invalid syntax (port-list disable is not a valid command). Option D (config system npu) is not the standard method for granular troubleshooting.

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.

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Using-the-diagnose-sys-top-CLI-command/ta-p/190238

https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-How-to-troubleshoot-FSSO-agentless-polling/ta-p/214349

From the snippet we can see that FortiGate (via the fssod daemon) is directly detecting the user logon rather than relying on a separate “collector” or “DC agent.” This indicates agentless polling—FortiGate polls the DC’s event logs over TCP 445 to discover logons. So: - FSSO is using agentless polling mode to detect logon events - In agentless mode, FortiGate will periodically poll the same IP (the DC) on port 445 to see if the user is still logged on

When FortiGate performs SSL certificate inspection with default settings, it checks if the Server Name Indication (SNI) matches either the Common Name (CN) or any Subject Alternative Name (SAN) in the server certificate. If there is no match, FortiGate does not block the connection; instead, it uses the CN value from the certificate's subject field to continue web filtering and categorization.

This behavior is described in the official Fortinet 7.6.4 Administration Guide:

“Check the SNI in the hello message with the CN or SAN field in the returned server certificate: Enable: If it is mismatched, use the CN in the server certificate.” This is the default (Enable) mode, which differs from the Strict mode that would block the mismatched connection.

By default, this policy ensures service continuity and prevents disruptions due to certificate mismatches, allowing FortiGate to log and inspect based on the CN even when the requested SNI does not match. It provides a balance between connection reliability and the accuracy of filtering by certificate identity, allowing security policies to remain functional without unnecessary blocks. This approach is recommended by Fortinet to maintain usability for end-users while still supporting granular inspection.

According to Fortinet’s LDAP authentication workflow as described in the FortiOS Administration Guide and the official LDAP debug log interpretation, each authentication attempt is split into several key steps: Bind Request, Search Request, and then, if successful, a Bind as the found user DN. In the provided debug output, we see "start search_dn-base" with a filter "sAMAccountName=jsmith" and the log line "Going to SEARCH state," confirming that FortiOS is in the second step—the Search Request (Option D). Official documentation highlights this exact phrase "SEARCH state" as indicative of Step 2 within the LDAP process (“Bind → Search → Bind”).

Additionally, the last line “Found DN 1: CN=John Smith, CN=Users, DC=TAC, DC=ottawa, DC=fortinet, DC=com” verifies that the system has successfully mapped the username to the Distinguished Name (DN) and this user is “John Smith.” The authentication will now proceed using this mapped user (Option B). Fortinet’s logs record the found DN after a successful search, which is a strong confirmation that the user’s credentials can be validated against the found DN.

Options A and C are not supported directly by the debug output shown:

The server name "Lab" is referenced as part of the request, but not explicitly as the LDAP server’s configured name in this output.

Step 3 (Bind Request) would follow finding the DN, but the log here demonstrates the Search and DN found—per Fortinet, this precedes the actual Bind/validation step.

The reported symptom—users unable to access any websites despite no explicit blocks in the profile—points to systemic connectivity or configuration issues rather than specific URL filtering rules.

Option B (SSL/TLS Inspection): When Deep Inspection is enabled, the FortiGate acts as a Man-in-the-Middle (MitM) and re-signs server certificates using its own CA. If the clients (browsers) do not trust this CA (i.e., the certificate is not installed in their Trusted Root store), they will reject the connection with certificate errors, effectively preventing access to all HTTPS websites.

Option D (DNS): Web browsing relies on DNS resolution. If the configured DNS server is unreachable or failing, the FortiGate (or the client) cannot resolve FQDNs to IP addresses. Consequently, browsers will fail to load any page, resulting in a total loss of web access.

Option E (License): If the FortiGuard Web Filtering license expires, the FortiGate can no longer query the FortiGuard Distribution Network (FDN) for ratings. By default, or if the allow-when-rating-error setting is disabled (a common security practice), the FortiGate will block all web traffic that it cannot rate, often displaying a "Web Filter Service Error" or invalid license page.

Option A is incorrect because clearing the cache only increases latency, it does not block traffic. Option C is incorrect because webfilter-force-off is typically used to disable the service (often allowing traffic to bypass checks if the service is down), rather than blocking it.

To determine why sessions are being removed, we must interpret the specific counters in the diagnose sys session stat output provided in the exhibit.

Analyze memory_tension_drop (Reason A):

Observation: The output shows memory_tension_drop=4.

This counter specifically increments when the FortiGate kernel attempts to allocate a new memory page for a session but fails due to a lack of available system memory. As a result, the session creation is aborted or an existing session is dropped to free up resources. This confirms that the kernel is struggling to allocate memory pages.

Analyze extreme_low_mem (Reason D):

Observation: The output shows extreme_low_mem=0 (which is good), but we must look at the context of memory_tension_drop.

Context: While the extreme_low_mem counter itself is 0 in this snapshot, the presence of memory_tension_drop indicates the system is under memory pressure. Furthermore, in many Fortinet exam contexts involving this specific exhibit, the focus is on the mechanism of "flushing sessions" to recover memory.

Refinement: Actually, look closer at the exhibit. It shows flush=787.

The flush counter indicates the number of times the system has actively purged (flushed) old or stale sessions from the table to recover memory or due to policy changes. A high flush count combined with memory tension drops strongly suggests the system is aggressively removing sessions to handle high memory usage. Therefore, "FortiGate is flushing sessions because of high memory usage" is the correct interpretation of the flush and memory_tension_drop counters working together.

Why other options are incorrect:

B: There is no counter in this specific output (like tcp_syn_sent drop) that indicates dropping incomplete handshakes. The clash=0 and delete=0 counters are low/zero.

C: The dev_down=16/120 field does not mean the device was down for 10 seconds. It refers to device index pointers or internal kernel interface states, not system uptime/downtime impacting session acceptance in the way described.

Based on the Fortinet FCSS - Network Security 7.6 documents and standard exam content for these specific troubleshooting scenarios, here are the verified answers.

Questions no: 74

Verified Answer: A, C

Comprehensive and Detailed Explanation with all FCSS - Network Security 7.6 documents:

This question typically refers to a session table exhibit showing Local Traffic (traffic originating from or destined to the FortiGate itself, such as management traffic, DNS queries initiated by FortiGate, or dynamic routing updates). These sessions are identified by Policy ID 0 or the absence of a forwarded interface pair (e.g., local flag).

C. FortiGate either initiated the session or the session terminates at FortiGate:

This is the definition of Local Traffic. Unlike Forward Traffic (which passes through the FortiGate from one interface to another), local traffic belongs to the FortiGate's control plane (e.g., an administrator logging in, or the FortiGate connecting to FortiGuard).

In the session table, this is characterized by policy_id=0 or the source/destination being the FortiGate's own IP.

A. FortiGate is performing a security profile inspection using the CPU:

Local traffic and traffic requiring complex handling (like the application notification app_ntf seen in similar exhibits) are processed by the CPU (Kernel) rather than being fully offloaded to the NPU (Network Processor) fast path.

The NPU cannot handle local host traffic (traffic destined to the FortiGate CPU). Therefore, the CPU must process these packets.

Why other options are incorrect:

B: Captive portal redirection involves specific authentication flags and HTTP redirection, usually seen as a forwarding decision, not a completed local session.

D: "Forwarded without inspection" describes an offloaded or fast-pathed session (NP6/NP7), which would not be local traffic and would show hardware offload flags (e.g., np6_0).

When the "auxiliary session" setting is enabled (typically via config system npu or implicitly for ECMP on NP6/NP7 processors), the FortiGate alters how it manages sessions to support hardware offloading for traffic that might switch interfaces (like ECMP or SD-WAN).

B. FortiGate accelerates all ECMP traffic to the NP6 processor:

The primary purpose of enabling auxiliary sessions is to ensure that ECMP traffic can be fully offloaded (accelerated) by the NPU. Without auxiliary sessions, if the kernel or routing engine switches a flow to a different outgoing interface (due to load balancing), the NPU might not recognize the flow for that new interface and would send the packet back to the CPU (slow path). Auxiliary sessions prevent this by pre-populating the NPU with the necessary information for all valid paths.

D. FortiGate creates two sessions in case of a routing change:

Technically, the FortiGate creates the primary session (for the currently selected path) and an auxiliary session (for the alternative path). In a standard two-path ECMP scenario, this results in "two sessions" existing in the session table for the same flow. This ensures that if a routing change occurs (e.g., the flow shifts to the second path), the traffic continues to be processed by the NPU without interruption or re-evaluation by the CPU.

When the FortiGate enters Conserve Mode due to high memory pressure (specifically reaching the Extreme Threshold at 95% memory usage, or the Red Threshold for proxy traffic), the system prioritizes stability and preventing a system crash (kernel panic).

D. FortiGate begins dropping all new sessions to protect resources:

In Extreme Conserve Mode (95%), the FortiGate kernel acts to preserve the remaining memory for system-critical tasks (like admin access and basic packet forwarding of existing sessions). To achieve this, it drops all new session initiation requests regardless of the inspection type.

In Red Conserve Mode (88%), it specifically drops new sessions that require proxy-based inspection (as these consume the most memory), while often still allowing flow-based traffic.

Among the provided choices, "dropping new sessions" is the only standard protective mechanism FortiOS employs to stop memory usage from climbing further.

Why other options are incorrect:

A: FortiGate does not automatically reboot in conserve mode; it attempts to recover by restricting traffic. (Reboot is a last-resort crash, not a configured action).

B: Inspection modes (Proxy vs. Flow) are defined in firewall policies and cannot be dynamically switched by the system during runtime.

C: The system does not arbitrarily stop "non-essential processes" like logging or AV. Logging is critical for audit trails. While av-failopen can be configured to bypass scanning, the system typically defaults to "Fail-Close" (dropping traffic) rather than stopping the engines themselves.

To display debug output on FortiGate devices, you must always run both the application-specific debug command and the global debug enable command. The command diagnose debug application ike -1 sets up the detail level for the IKE daemon debug, but it does not display any debug output on its own. As described in the FortiOS CLI debugging manuals, the command diagnose debug enable activates debug output on the console, making all previously set debugs visible. This is especially important for VPN troubleshooting—without the enable command, no output appears even if there is VPN traffic.

The correct diagnostic sequence is:

diagnose debug application ike -1

diagnose debug enable

This procedure is found in every FortiOS CLI debug tutorial and troubleshooting workflow.

According to the official Fortinet documentation (Technical Tip: Useful FSSO Commands), heartbeat messages play a crucial role in communication between the FSSO Collector Agent and FortiGate. These messages are regularly sent from the Collector Agent to verify its status, maintain session awareness, and confirm connectivity between the authentication infrastructure and FortiGate appliances.

Option B is confirmed by Fortinet, as the collector agent logs on Windows or its management console will specifically note heartbeat events, connection status, and any issues maintaining contact with FortiGate units.

Option C is validated by both official CLI documentation and the technical tip linked. On FortiGate, heartbeat messages from the collector agent are visible using real-time debug tools such as diagnose debug application authd or FSSO-specific commands. These enable administrators to monitor live logon states, session status, and connection health directly from the FortiGate CLI. The debug stream shows heartbeats received and their effect on active logons, associating health monitoring with active sessions.

Heartbeat operation is fully automated once FSSO is set up—there is no requirement for manual enablement or configuration, aligning with Fortinet’s philosophy of seamless integration and centralized management across the Security Fabric. This ensures that both FortiGate and the collector agent can quickly and reliably detect any miscommunication or outage, addressing authentication issues proactively.

The exhibit for question 4 shows a policy route table entry, and key fields are as follows:

internet service(1) : Fortinet-FortiGuard(1245324,0.0.0.0,0.0.0.0)

According to the Fortinet official documentation, when a policy route is based on Internet Service Database (ISDB) entries, the route entry will specifically mention “internet service,” showing the service being referenced (in this example, Fortinet-FortiGuard). This is fundamentally different from a regular policy route, which is defined by source, destination, and service wildcards without referencing an ISDB signature. A regular policy route's output would not contain the line “internet service.”

Policy routes that use ISDB allow FortiGate to steer traffic for specific well-known services (like FortiGuard, Google, Microsoft) based on traffic pattern recognition, even if the destination IP is dynamic. The matching and route selection follow the ISDB tag and can coexist with static or regular policy routes.

Thus, this entry is correctly and uniquely an ISDB route, as explained in the FortiOS policy routing documentation and ISDB configuration references.