Chapter 1 What’s New for FortiOS 5.0 : IPv6 : IPv6 NAT – NAT64, DNS64, NAT66
  
IPv6 NAT – NAT64, DNS64, NAT66
NAT66, NAT64 and DNS64 are now supported for IPv6. These options provide IPv6 NAT and DNS capabilities IPv6-IPv4 tunnelling or dual stack configurations. These are available only in the CLI.
Fortinet supports all features described in RFC 6146. However, for DNS64 there is no support for handling Domain Name System Security Extensions (DNSSEC). DNSSEC is for securing types of information that are provided by the DNS as used on an IP network or networks. You can find more information about DNS64 in RFC 6147.