Pass the Fortinet Fortinet Certified Solution Specialist FCSS_NST_SE-7.6 Questions and answers with CertsForce

The administrator is running a packet sniffer with the filter ' udp port 500 or udp port 4500 or esp ' . The result is " no output, " even though the VPN is attempting to establish (failing).

A. The VPN is configured to use IKE over TCP:

Standard IPsec IKE negotiation uses UDP port 500 (IKE) and UDP port 4500 (NAT-T).

However, if IKEv2 over TCP (RFC 8229) or Fortinet ' s proprietary IKE over TCP is configured (often used to bypass firewalls that block UDP), the traffic will use TCP (often port 4500 or 443).

The sniffer filter explicitly looks for udp or esp (IP Protocol 50).

If the traffic is encapsulated in TCP, it matches tcp protocol, not udp or esp (raw ESP). Therefore, the sniffer sees zero packets matching the filter.

Why other options are incorrect:

B: esp is a valid argument for diagnose sniffer packet. It is equivalent to filtering for IP protocol 50.

C: If the ISP were blocking traffic, the sniffer (running on the local FortiGate) would still see the outbound packets generated by the FortiGate trying to initiate the connection. " No output " implies the local device isn ' t even generating packets matching that filter.

D: Mismatched IKE versions would still generate IKE negotiation packets (proposals/errors) that would be captured by the sniffer.

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%

https://community.fortinet.com/t5/FortiGate/Technical-Tip-FortiGate-Static-URL-filter-actions-explained/ta-p/206632

The output on FGT-01 confirms that the device is actively encapsulating traffic and sending it as ESP packets (Protocol 50) out of port1 towards the IP address 97.86.16.52. The logs show outgoing packets, which confirms FGT-01 is attempting to initiate or maintain the tunnel and that NAT-Traversal is not being used (as it uses raw ESP).

The output on FGT-02 , however, displays (no packets captured). This is significant because the sniffer command diagnose sniffer packet any ' esp ' captures traffic at the network interface level (ingress), regardless of whether a matching VPN configuration exists on the receiving unit. The absence of packets proves that the ESP traffic generated by FGT-01 is physically not arriving at FGT-02 ' s interface.

This behavior is explained by two primary factors:

Option A (Blocking): An intermediate device, such as an ISP router or firewall, is dropping Protocol 50 traffic. Unlike UDP 500/4500, raw ESP is often blocked by default on many networks or legacy devices.

Option C (Routing/Misconfiguration): If the administrator configured the wrong remote peer IP on FGT-01 , the packets are being routed to a different destination entirely. Consequently, they never arrive at FGT-02 to be captured.

Option B is incorrect because even without a configured VPN tunnel, the sniffer would still display the incoming ESP packets if they were reaching the interface. Option D is incorrect because FGT-01 is sending ESP, making ' esp ' the correct filter.

The correct answer is A .

The debug output is for an HTTPS request and shows a hostname value. The study guide explains that with SSL certificate inspection, FortiGate extracts the FQDN from either:

“TLS extension server name indication (SNI)”

“SSL certificate common name (CN)”

So the hostname shown in the real-time web-filter debug can be derived from the SNI in the client request or, if needed, from the CN in the server certificate. That makes A correct.

Why the other options are wrong:

B is wrong because the study-guide example for web-filter real-time debug explicitly says: “This slide shows an example of real-time debug output when the URL to categorize isn ' t in the FortiGuard cache.” In these debugs, cat=255 appears before the final lookup result, so this does not indicate a local-cache hit.

C is wrong because ftgd-allow is the action , not the profile name. The debug line shows the action as action=9 (ftgd-allow) while the profile shown is profile= ' default ' . FortiOS web-filter logs also use the profile field separately from the action field

D is wrong because the final category shown is url_cat=52 , not 255. The study guide’s example shows the same pattern: an initial cat=255 in the request line, followed by the resolved result cat=52 url_cat=52

So the verified answer is: A .

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.

For Option A:In Fortinet BGP (and standard BGP), when a prefix is displayed with an " i " (lowercase i) in the Path column, it represents an internal prefix that originated from the local router, typically configured via the BGP " network " command. In the exhibit, the prefix 10.20.30.0/24 is listed with a Path value of i, indicating it was injected into BGP by the local router using the network statement, not via redistribution from another routing protocol. The same logic applies to i as documented: " Origin code ' i ' means the route was injected via the network command. "

For Option D:The get router info bgp network output is a summary table displaying both local and received BGP routes. It lists all known routes to the BGP process, whether received from peers or originated locally. The exhibit shows all BGP prefixes known to the local router, matching the official admin guide’s description of this command’s output.

Explanation for B and C:

The phrase “legacy route advertisement” is not formalized in BGP documentation or Fortinet’s admin guide; the output uses standard BGP mechanics.

If a route was redistributed into BGP from another routing protocol, the Path field would display a " ? " (question mark) for incomplete (redistributed) origin. Here the /24 route has " i " so it is NOT a redistribution.

The Internet Key Exchange version 2 (IKEv2) protocol simplifies the negotiation process compared to IKEv1. It is defined by a specific sequence of message exchanges to establish a secure IPsec tunnel.

The correct chronological order of the IKEv2 exchanges is:

IKE_SA_INIT (Initial Exchange):

This is the first exchange. It negotiates the security parameters for the IKE Security Association (IKE SA), sends nonces, and performs the Diffie-Hellman key exchange. At the end of this exchange, the communication is encrypted, but the peers are not yet authenticated.

IKE_AUTH (Authentication Exchange):

This is the second exchange. It authenticates the previous messages, exchanges identities and certificates (if used), and establishes the first Child SA (the actual IPsec Security Association used for data traffic).

CREATE_CHILD_SA (Subsequent Exchanges):

This exchange occurs after the IKE SA and the initial Child SA are established. It is used to create additional Child SAs (for different traffic selectors) or to perform re-keying for the IKE SA or existing Child SAs.

Why other options are incorrect:

A & B: Incorrect because CREATE_CHILD_SA cannot happen before the SA is initialized (IKE_SA_INIT) and authenticated (IKE_AUTH).

D: Incorrect because IKE_AUTH cannot occur before IKE_SA_INIT.

Therefore, the protocol flow is IKE_SA_INIT $\rightarrow$ IKE_AUTH $\rightarrow$ CREATE_CHILD_SA.

The study guide identifies this exact output as an expectation session created by the FTP session helper :

“run helper-ftp” indicates the FTP helper is in use.

“FortiGate created an expectation session and opened the pinhole port for the expected return traffic”

It also explains why this exists:

“Another important function of the session helper is to temporarily create an expected session (or pinhole) for the data channel connection that comes from the server.”

“The session helper automatically creates the session and opens the door for the incoming connection.”

“These incoming TCP sessions use random TCP port numbers.”

That directly proves C is correct.

For A , the exhibit shows expire=23. The study guide explains the expire field as the length of time until the session expires if no matching traffic arrives, and the FortiOS guide states for expectation sessions:

“Expectation sessions usually have a timeout value of 30 seconds. If the communication from the server is not initiated within 30 seconds the expectation session times out and traffic will be denied.”

So with expire=23, FortiGate will allow that expected traffic only for the remaining 23 seconds; after that, it times out and the traffic is denied. That makes A correct.

Why the other options are wrong:

B is not supported . The study guide describes expectation sessions as being created by the session helper from the control-session negotiation, not as independent objects unaffected by the master session.

D is wrong as stated. Even though the output contains policy_id=25, the study guide explicitly says the incoming expected connection is allowed by the expected session itself, “even when no firewall policy allows it.”