IPv6 DHCP on wan1 interface not working? How to fix this?

Hi,

I have an ISP that has a rd6 /60, but when I look at the router advertisements I see it announces a prefix /64.

All my client machines, MAC, Windows and Linux all work perfectly fine with the IPv6 addresses within that prefix and have 2 IP addresses (temporary and regular).

My goal would have been:

1) WAN1 interface should accept the router advertisement and assign itself (SLAAC) an IPv6 address.

I cannot get this to work.

I tried to use mode dhcp and used also some other settings, but it never accepted an IPv6 with that prefix. Rebooting after the changes also did not work.

If I manually assign an IPv6 address and route, IPv6 works fine. 

What am I doing wrong?

2) I should be able to allow other ports to use the same IPv6 prefix, but going through Fortigate.

The option I saw is someting like a ND proxy?

What other options are there?