No idea. I've tried every setting combination on this consumer grade D-Link router which is supposed to support IPv6. Nothing results in a functioning network. Forum posts I find from other customers of this ISP report the same behaviour on other routers. The modem gets a /56 at least, and hands out addresses from a /64 range under that I assume, the router gets a /128 from the modem, and then gives up entirely on doing anything with IPv6.