FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
The article recommends that the HA management IP address is not used for managing FortiGate cluster over FortiManager.
Do not use the "ha-mgmt-interface" IP address for adding FortiGate cluster to FortiManager as managed device. The HA management IP address is unique for each cluster member. If the FortiGate cluster performs failover to the secondary cluster unit, the FortiGate will not be manageable from FortiManager. .
FMG --- FortiGate_HA_Cluster
config system ha (…) set ha-mgmt-interface "port1" (…)