IPv6 with Prefix Delegation on Fortigate

[Edit 2018-10-18] Make sure to use FortiOS 6.0.3 or later for this, as earlier versions of 6.0.x will force your interface to IPv6 “static” when you make any change to the interface from the GUI, including changes to its IPv4 configuration, such as a DHCP reservation. I have not tested 5.6.x but am assuming it […]