Figure 190 shows a typical FortiGate-620B HA cluster consisting of two FortiGate‑620B units (620_ha_1 and 620_ha_2) connected to the same internal (port2) and external (port1) networks.
Port3 and port4 are the default FortiGate-620B heartbeat interfaces. Because the cluster consists of two FortiGate units, you can make the connections between the heartbeat interfaces using crossover cables. You could also use switches and regular ethernet cables.