IPv6, Central NAT, and SD-WAN and matching them to my local FD00: IP addresses.

[ameif56hgt]

I've searched everywhere, but can't resolve this question.

I have TWO ISP's that each use IPv4 and IPv6.  With IPv4, each ISP gives you one public address and on your network, you assign local IP addresses that can stay fixed, 192.168.1.X. for example.  Then Central NAT converts from each device's local IP to their public IP. Life is good.

With IPv6 it's a different ballgame. You get a delegated group of IPv6 addresses that you give to your devices, and you don't use NAT. If you have TWO ISP's, and a SD-WAN, I guess you could give each device two IP's addresses, one from each ISP.  I Guess you can do that.

But in my network, these IPv6 addresses change, so I want my devices to use a fixed IPv6 address given out.  SLAAC does this, and I give all my devices a fd00::xxxx. address. OK works great.  

So, how do I set up Central NAT to translate between each devices fd00::xxxx IPv6 address and a list of delegated IP addresses from each ISP?  And I use SD-WAN for both ISPs for reliability and speed.  I don't see how to do that in IPv6.  Am I looking at this wrong??  I am an IPv6 newbie. 

[ameif56hgt]

I should say, Central NAT lets me pick "outgoing interface IP" which works great for IPv4 but I don't think IPv6.  I can use an "IP Pool" but it looks like those pools are fixed, and I'm sure my delegated IP range for IPv6 changes.  So that won't work.