- On the primary FortiGate, go to System > Settings and change the Host name to identify this as the primary FortiGate in the HA cluster.
- Go to System > HA and set the Mode to Active-Passive. Set the Device priority to a higher value than the default (in the example, 250) to make sure this FortiGate will always be the primary FortiGate. Also, set a Group name and Password.
Make sure you select Heartbeat interfaces (in the example, port3 and port4). Set the Heartbeat Interface Priority for each interface to 50.
Since the backup FortiGate isn't available, when you save the HA configuration, the primary FortiGate forms a cluster of one FortiGate but keeps operating normally.
If these steps don't start HA mode, make sure that none of the FortiGate interfaces use DHCP or PPPoE addressing.
If there are other FortiOS HA clusters on your network, you may need to change the cluster group ID, using this CLI command:
config system ha
set group-id 25