[c-nsp] IPv6 BGP Dual Homed dual site

[Scott Voll]

I'm trying to wrap my head around the best way to setup BGP with IPv6

We currently have two different ISP's connected to two different sites.
 then we run iBGP between the sites.

so in an IPv4 world have a class C at each location.  then at each location
my Firewalls NAT to the correct Class C as they exit my network.

This way if the link between sites go down I'm not black holing the other
sites because each site has it's own Class C it's announcing.

Now if I have a single /40 and I'm subnetting it per location(eg /44), but
all the other sites behind these sites are within that /40 how do I make
sure I don't end up blackholing the other site(s)?  Does that make sense?
 Do I need to announce a /44 from each site?  if so, that will kill my
meshed network(internal) if one site(external) goes down, or the WAN links
go down.

Thanks for any ideas.  Is there a best practice for this kind of setup?

TIA

Scott