I have fibre and a 4G connection and a pfsense firewall/router.
With IPv4 I can have failover and use the 4G if the fibre fails (Not likely, but it's mostly for fun^H^H^Hlearning purposes)
The pfsense takes care of this. I then get different public ipv4-addresses, but that doesn't matter, as I'm using NAT anyway.
I have also setup a tunnel on each connection, both to the same HE POP (Germany), but I don't think I can have true failover, because IPv6 is not using NAT, so each internal machine have to have an address in the right subnet.
Unless the other end could route my internal subnet through either connection, whichever was up, and things doesn't work like that out of the box, right?
I guess if I was serious, I'd get a ASN and do BGP, and then the two tunnels should go to different HE POP's.
Or am I missing something?
Can windows and linux get ipv6-addresses in two subnets, and failover if one fails?
Every other time this question was asked, the answer was to do BGP. I'm not familiar with the specifics of what you're trying to do, but I would guess that answer also applies here too.