Re: @Novex
> You see: my router supports IPv6 on the outside (also has an IPv6 address) but only provides IPv4 on the inside. It gets more bizarre: my IPv6 address is an /128 one. In other words: one fixed address, I'd have expected some kind of subnet for sure.
Name and shame the provider?
* It might be that they are indeed routing a /64 or larger subnet towards your router, and need to manually configure the LAN side of the router with this block. (Only if the ISP gives you a static IPv6 range)
* It might be that your router is expected to use DHCPv6 to learn and apply the /64 assignment, but is not currently configured to do so.
* It might be that you have the whole /64 which contains that /128, and you just need to configure your LAN side with that range (icky, but some providers do it). This is more likely if your /128 ends with ::2 or ::1
It depends if the ISP is also responsible for configuring your router. If they are, then maybe they've done a half-assed job.
But if you bought and installed your own router, then maybe you have to do more stuff to get IPv6 to work.