Figure 149 shows a Transparent mode FortiGate HA cluster consisting of two FortiGate units (FGT_ha_1 and FGT_ha_2) installed between the Internet and internal network. The topology includes a router that performs NAT between the internal network and the Internet. The cluster management IP address is 10.11.101.100.
Port3 and port4 are used as the 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.