A company is deploying a FortiGate HA cluster in active-passive mode across two data centers. The network team reports that after a failover, some existing TCP sessions are dropped. Which configuration change should be applied to maintain session persistence during failover?
Session sync shares session state between primary and secondary, maintaining sessions during failover.
Why this answer
In an active-passive HA cluster, session synchronization (config.sys ha session-sync) ensures that TCP session state information is replicated from the active unit to the passive unit. Without this, the passive unit has no knowledge of existing sessions after a failover, causing them to be dropped. Enabling session synchronization allows the new active unit to continue forwarding traffic for established sessions seamlessly.
Exam trap
The trap here is that candidates often confuse gratuitous ARP (which handles Layer 2 updates) with session persistence, assuming that updating MAC tables is sufficient to maintain TCP sessions, but session state must be replicated at Layer 4.
How to eliminate wrong answers
Option B is wrong because disabling NAT inspection does not affect session persistence during failover; NAT is a separate function and does not control session state replication. Option C is wrong because gratuitous ARP is used to update the network with the new MAC address of the virtual IP after failover, but it does not preserve existing TCP sessions; it only ensures Layer 2 reachability. Option D is wrong because increasing the heartbeat interval to 2 seconds would actually slow down failure detection, potentially increasing session loss, and has no impact on session synchronization.