The range of the FortiGate-7000F HA group ID has been increased to 0 to 255:
config system ha
set group-id 0-255
The HA group ID is used to calculate the MAC addresses assigned by the FGCP to the FortiGates in an FGCP cluster. Because of this change to the group ID range, after upgrading a FortiGate-7000F FGCP cluster to FortiOS 6.4.8, the MAC addresses assigned to the cluster interfaces by the FGCP will not be the same as the MAC addresses that were assigned before the firmware upgrade.
If you have upstream devices that perform MAC address checking and enforcement, traffic may be interrupted after the firmware upgrade because of the new MAC addresses.