Fortinet fortigate-100a Benutzerhandbuch

You can assign both an IPv4 and an IPv6 address to any interface on a FortiGate unit. 
The interface functions as two interfaces, one for IPv4-addressed packets and 
another for IPv6-addressed packets.

FortiGate units support static routing, periodic router advertisements, and tunneling of 
IPv6-addressed traffic over an IPv4-addressed network. All of these features must be 
configured through the Command Line Interface (CLI). See the FortiGate CLI 
Reference Guide for information on the following commands:

Interface configuration, including periodic 

router advertisements

config system interface
See the keywords beginning with “ip6”.
config ip6-prefix-list

Static routing

config router static6

IPv6 tunneling

config system ipv6_tunnel