Active-passive and active-active HA
The first decision to make when configuring FortiGate HA is whether to choose active‑passive or active-active HA mode. To configure the HA mode, go to System > Config > HA and set Mode to Active-Passive or Active-Active.
From the CLI enter the following command to set the HA mode to active-passive:
config system ha
set mode a-p
end
To form a cluster, all cluster units must be set to the same mode. You can also change the mode after the cluster is up and running. Changing the mode of a functioning cluster causes a slight delay while the cluster renegotiates to operate in the new mode and possibly select a new primary unit.