The FireBrick makes sending IPv6 over IPv4 tunnels very very simple. A route statement is all you need and you can even do it via BGP if feeling adventurous (next hop in 2002::/16).
Because of that we had the office and Maidenhead (MH) tunneled from London (THN) still. This is the case since many years ago when we first set up Maidenhead and the transit provider did not do IPv6. The route announcements on subnets even did 1480 MTU to simplify matters.
It just works so we had not changed anything even though it has been a year or so that the carrier did IPv6.
Anyway, in a burst of activity to clear the white board of one more item, Paul set up IPv6 transit today, and I went through the config moving things off tunnels.
It is interesting. If we announce a /48 from here we see it "on the Internet", and importantly transit in London and HE in London. If we announce any smaller we do see it, but only from the peering with the Maidenhead carrier. So their upstream filters smaller than /48. Not a huge surprise but nice to know. Anyone filtering larger than /48 would route to THN and from there to MH. So not an issue.
Right now we have some sub /48 blocks in MH, but that will change. Customer routing in MH is all on a dedicated /48 so no issue. I suspect we'll move to a separate /48 for MH soon. It means a bit of renumbering, but nothing too drastic.
Anyway, nice to have clean 1500 MTU IPv6 at home at last. Something our customers have had for a long time now. 10th year of IPv6 to broadband lines you know, and all that...
Next stop - new IPv4 /24 and IPv6 /48 PI at home... And why not?