FCSS_NST_SE-7.6 Exam Dumps - Fortinet NSE 6 - Network Security 7.6 Support Engineer

The Network Security Support Engineer 7.6 Study Guide explicitly explains this debug message:

“iprope_in_check() check failed, drop” means the packet is destined to a FortiGate IP address and one of these conditions applies:

The service is not enabled

The service is using a different TCP port

The source IP address is not included in the trusted host list

The packet matches a local-in policy with action deny

That directly confirms C. Trusted host list misconfiguration .

Why D is the second valid choice:

The FortiOS administration guide explains that:

“IP pools and VIPs are considered local IP addresses if responding to ARP requests on these external IP addresses is enabled … the FortiGate is considered a destination for those IP addresses … once an IP pool or VIP has been configured … the FortiGate considers it as a local address and will not forward traffic based on the routing table.”

Because iprope_in_check() is a local-in/local-destination type failure, a VIP or IP pool misconfiguration can cause traffic to be treated as destined for the FortiGate itself, which can then trigger this drop condition if the matching local service/local-in handling is not valid. So D is the closest supported second answer from the available choices.

Why the other options are wrong:

A is wrong because policy route problems are not the documented meaning of this specific debug message. The study guide instead ties iprope_in_check() check failed, drop to management/local-in conditions.

B is wrong because the study guide says traffic shaping drops appear as: “Denied by quota check”

To determine the cause of the failure, we must analyze the IKEv2 debug output provided in the exhibit (image_ad3dc6.jpg):

Identify the Negotiation Phase:

The debug log shows: responder received CREATE_CHILD exchange.

In IKEv2, the CREATE_CHILD_SA exchange is used to create new Child SAs (Phase 2) or to rekey existing ones.

The fact that the tunnel was previously " brought up successfully " implies the initial IKE SA (Phase 1) is stable, and this error is occurring specifically during a rekey event, which often involves Perfect Forward Secrecy (PFS).

Analyze the Proposals (The Mismatch):

Incoming Proposal (Remote Peer):

The remote peer sends a proposal containing two Diffie-Hellman groups: type=DH_GROUP, val=MODP2048 (Group 14) and type=DH_GROUP, val=MODP1536 (Group 5).

My Proposal (Local FortiGate):

The local FortiGate configuration expects: type=DH_GROUP, val=MODP3072 (Group 15).

Result of the Negotiation:

The debug output concludes with: no proposal chosen and Negotiate SA Error.

This error occurs because the local FortiGate cannot find a common Diffie-Hellman group between what it requires (Group 15) and what the peer is offering (Groups 14 or 5).

While this is technically a mismatch occurring during the Phase 2 (Child SA) creation, " A Diffie-Hellman mismatch " (Option A) is the precise root cause identified in the logs.

Why other options are incorrect:

B: The log shows received create-child request, confirming that UDP traffic is reaching the device and is not blocked.

C: The failure is in the CREATE_CHILD exchange (Phase 2/Rekey), not the IKE_SA_INIT or IKE_AUTH (Phase 1) exchanges.

D: While the mismatch is occurring within the Phase 2 definitions, Option A is the specific technical reason for the no proposal chosen error shown in the DH_GROUP lines.

The get router info ospf database brief output on FGT-2 clearly indicates that Area 0.0.0.5 is configured as a [Stub] area.

In OSPF, a Stub Area is specifically designed to reduce the size of the Link State Database (LSDB) on internal routers. The primary behavior of a Stub area is that it does not accept Type 5 (AS External) LSAs .

FGT-3 is the ASBR (Autonomous System Border Router) and is importing static routes, which are generated as Type 5 LSAs in the OSPF domain.

FGT-1 acts as the ABR (Area Border Router). Because Area 0.0.0.5 is a Stub area, FGT-1 blocks these Type 5 LSAs from entering Area 0.0.0.5.

Consequently, FGT-2 will not receive the specific external routes advertised by FGT-3. Instead, the ABR (FGT-1) injects a default route (0.0.0.0/0) into the Stub area to allow connectivity to the external world, which is visible in the database output.

While the question text mentions FGT-3 not receiving routes, the definitive configuration shown in the exhibit is the Stub area setting, which directly corresponds to the blocking of Type 5 LSA propagation (Option A).

The exhibit displays the output from the diagnose debug rating command on a FortiGate device. This command is used to display information about FortiGuard Web Filtering or other security-related queries performed by FortiGate to FortiGuard servers. Official Fortinet documentation outlines the meaning of each field in the server list. The FortiGate maintains a list of available FortiGuard servers, selecting the optimal server based on factors such as weight, round-trip time (RTT), and regional settings.

The very first entry in the server list after " Server List " is the server FortiGate initially uses, prioritized by factors such as proximity and RTT. Here, 64.26.151.37 is listed first, and the FortiGuard-requests value confirms that this server handled the highest number of requests.

The IPs, weights, and lost/failed counters are monitored for server performance and selection over time. FortiGate ' s default operational logic is to try the first entry for contract validation and use the next in the list if the first is unavailable or has high latency or packet loss.

There is no direct correlation between the Weight and the number of FortiGuard-requests. The servers with higher or lower weights may still handle different request volumes based on availability and performance.

The TZ (time zone) value ' s sign (positive or negative) does not affect server preference; it is informational, showing the server ' s location relative to UTC, not a rating metric.

DNS query results for FortiGuard servers are not shown here, and the provided servers are not returned in DNS query order.

This command and interpretation are detailed in the FortiOS Administration Guide’s section describing FortiGuard server selection and contract validation processes.