Hello, Victor!

Monday June 28 2021 21:07, you wrote to All:

 VS> What if I had two IPv6-capable ISPs for my home, and a /64 or a /56
 VS> from each of them? Is it possible to setup a backup link this way?

Sure.

 VS> I know that my home router can advertise multiple global IPv6 prefixes
 VS> into the LAN, but how will LAN hosts failover to the backup gateway if
 VS> the primary ISP fails? They will have IPv6 addresses from both blocks,
 VS> which should they choose for their outgoing src address?

NPTv6 is the answer (RFC 6296).
Not sure if your router can handle it.

Best regards,
             dp.

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