You need to make sure your router is getting an IPv6 address on its wm0 interface, not just re0.
If you have a static IPv6 addr from the ISP, you can just configure another subnet for the other interface, and all should be fine. If you don't, you'll need to arrange for a prefix delegation from them, rather than just a single address (or more correctly, in addition to the address for re0) and then get that assigned to re0. This is likely to be a common config for IPv6 routers, but I don't believe that we currently have anything to automate it - when the current IPv6 and NetBSD config for it was created, it was accepted wisdom that routers were always configured by humans, and auto-config of a router was heresy. That's nonsense, of course, but I don't recall seeing anyone add the necessary support to NetBSD to make all of this be seemless - you may need to resort to some smoke and mirrors to get things working initially. kre
