Basic Concept: In active/active HA, HA links have distinct roles. HA1 handles control, HA2 synchronizes session state, and HA3 forwards packets between peers during asymmetric flows.
Why A is Correct: HA3 is correct because active/active peers may see different directions of a session; HA3 carries packets to the peer that owns or must process the session.
Why B is Wrong: To exchange hellos, heartbeats, HA state information, and management plane synchronization for routing and User-ID information is an HA-related setting or behavior, but it is not the specific HA link, LACP pre-negotiation option, or upgrade sequence required here.
Why C is Wrong: To synchronize sessions, forwarding tables, IPSec security associations, and ARP tables between firewalls in an HA pair is an HA-related setting or behavior, but it is not the specific HA link, LACP pre-negotiation option, or upgrade sequence required here.
Why D is Wrong: To perform session cache synchronization among all HA peers having the same cluster ID is an HA-related setting or behavior, but it is not the specific HA link, LACP pre-negotiation option, or upgrade sequence required here.
