Comprehensive and Detailed 150 to 200 words of Explanation From Exact Extract of FortiOS 7.6 documents:

According to FortiOS 7.6 High Availability documentation, the FortiGate Cluster Protocol (FGCP) provides robust mechanisms for both link monitoring and stateful data synchronization. Link failover is a primary trigger for cluster renegotiation; if a monitored interface goes down—including when an administrator manually sets the interface to administratively down—the primary unit's priority is effectively reduced, triggering a failover to a secondary unit to ensure path continuity.5 This is a standard method for testing HA failover behavior.

Furthermore, to achieve a seamless stateful failover where active sessions are not dropped, the FortiGate performs incremental synchronization of critical runtime data.6 This specifically includes Forwarding Information Base (FIB) entries, which represent the compiled routing table, and IPsec Security Associations (SAs).7 By synchronizing IPsec SAs, the secondary unit 8can resume encrypted tunnels immediately after a failover without requiring a f9ull IKE re-negotiation.10 Statement A is incorrect because in-band and out-of-band management can coexist using reserved management interfaces and management-ip settings.11 Statement C is incorrect because while heartbeat interfaces use link-local IPs in the 169.254.0.x range, the specific IP .2 is not universally required for all heartbeats and depends on the number of cluster members and serial numbers.