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

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 .

We must analyze the specific CLI output provided in the exhibit to determine the observations.

Analyze the Command and Output:

Command: # diagnose automation test HAFailOver

This command is used to manually trigger an automation stitch (named " HAFailOver " ) to verify its configuration and action execution. It simulates the trigger event to run the defined actions.

Output: automation test failed(1). stitch:HAFailOver

The output explicitly states that the test failed. The code (1) is a general error code indicating the execution did not complete successfully.

Evaluate the Options:

A. The configuration was backed up:

Incorrect. Since the test result is " failed " , the action defined in the stitch (which we can infer from the name " HAFailOver " is likely " Backup Configuration " ) was not successfully performed.

B. A high availability (HA) failover occurred:

Incorrect. The command diagnose automation test is a simulation tool. It does not indicate that a real physical HA failover took place; it only attempts to run the script associated with that event.

C. The test was unsuccessful:

Correct. The output clearly reads " automation test failed(1) " , which is the definition of an unsuccessful test.

D. The automation stitch test is not being logged:

Correct. In the context of Fortinet automation troubleshooting, a " failed(1) " result often occurs if the stitch is disabled or if the logging configuration required to trigger or record the stitch is not active. Consequently, the test execution is not properly logged in the automation history, or the failure implies a lack of necessary logging data to proceed. By elimination of the clearly incorrect options A and B, D is the second valid observation.

Based on the Fortinet FCSS - Network Security 7.6 documents and the analysis of the VPN tunnel exhibit, here is the verified answer.

Questions no: 91

Verified Answer: A, C

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

To determine the status of the VPN tunnel, we must examine the specific counters and fields in the diagnose vpn tunnel list output provided in the exhibit.

Analyze Phase 2 Status (Option A):

The output displays child_num=0.

In IKEv2 (and IKEv1 implementations in FortiOS), " Child SAs " refer to the Phase 2 (IPsec) Security Associations that carry the actual data traffic.

A value of 0 indicates that no Phase 2 tunnels are established. If Phase 2 were up, child_num would be at least 1.

Additionally, under the proxyid section, the field sa=0 confirms there is no active Security Association for that traffic selector.

Analyze Traffic Status (Option C):

The stat line shows: rxp=0 txp=0 rxb=0 txb=0.

rxp (Received Packets) and txp (Transmitted Packets) are both zero. This definitively confirms that no traffic is traversing the tunnel currently. This is expected since Phase 2 is down.

Analyze Phase 1 Status (Why B is incorrect):

The tunnel entry exists in the list with a valid tun_id, and NAT-Traversal is active (natt: mode=keepalive).

The presence of the tunnel in this command output, along with active Keepalive mechanisms, typically indicates that Phase 1 (IKE SA) is established and the peers are communicating on port 4500 (NAT-T), even though the data tunnels (Phase 2) failed to negotiate. If Phase 1 were down, the tunnel would often not appear in this " list " view or would show different status flags indicating a complete connection failure.

Conclusion: The exhibit shows a scenario where the Phase 1 control channel is likely up (evidenced by the entry existence and NATT keepalives), but the Phase 2 data channel is down (child_num=0), resulting in zero traffic flow (rxp=0/txp=0).