> Of course, with IPv4, you never assigned a large enough block to begin > with that would anticipate all growth, so routing additional blocks was > a lot easier than changing blocks, cleaner than secondary IPs > multiplying like crazy, etc., etc. None of that would be an issue with > a single /64.
You've hit on the key difference of IPv6. With IPv6 you should design your network so that it can grow for a long time without increasing the address block sizes anywhere. A /64 will work for even the biggest subnets. A /48 will do for for very, very big sites. And only the largest ISPs will outgrow a /32 allocation. If you assign a /48 to a data center site, then when you subnet it, try to maintain that growth ability if you can. Don't skimp on address block sizes unless you are backed into a corner for technical or business reasons. --Michael Dillon
