The session output includes the flag maydirty, which indicates that a security profile (in this case, application control, as shown by appvalid) is applied. When a failover occurs in a FortiGate HA cluster, sessions marked as maydirty are synchronized to the new primary device but must be re-evaluated against their respective security profiles to ensure security policy enforcement. The session is not dropped, but it undergoes this re-inspection process.

B. This is incorrect because the maydirty flag explicitly means the session requires re-evaluation by security profiles; it does not simply continue without any further processing.

C. The session does not show any allowederr packets, and this flag is not the reason for any specific failover behavior in this context. The session is synchronized, not removed.

D. While NAT is applied (nat=1), the primary reason for re-evaluation in this scenario is the application of security profiles, indicated by the maydirty flag, not the NAT status itself.

- FortiOS Handbook - High Availability 7.6, "Session failover" section. It explains that sessions with security profiles are marked as maydirty and are re-evaluated by the new primary after a failover.

- FortiOS Handbook - CLI Reference 7.6, diagnose sys session list command output fields. The description for dirty and maydirty flags confirms their role in session synchronization and re-evaluation.