Apologies in advance if I have misunderstood. -
I wouldn't set things up for a /56, stick with /64 for your lan, because as I understand it a fair number of systems assume a single lan is always a /64. The /56 is presumably to allow you to have multiple subnets or sites.
I have a /48 from Andrews and Arnold and the 16 bits above the low order 64 are to give me the facility to break the range up into multiple sites, so I could have 65536 offices! Currently I'm only using two or three /64s.
The original recommendation was that ISPs should be giving out /48s to everyone, which in my view is utter madness. Although 64 bits is a lot, we shouldn't be squandering the IPv6 address space at such a crazy rate that we end up using it all up and then having to renumber networks all over the place some day in order to repack the space properly. I would have thought that most domestic users have no interest in multiple sites, so a single /64 might be fine for them, and a /60 or /56 would be fine for really small businesses if they're never going to want more than 16 or 256 subsets.
At the rate they're going handing out /48s when Andrews and Arnold have a /32 for themselves, as many ISPs do, they're going to have to do something different as a limit of 65536 customers max (=48-32) isn't very sensible. Otherwise they'll have to get some more /32s which presumably won't be adjacent and so that means more difficulties with aggregation / summarisation, general routing table bloat, more difficult to use overarching ranges for firewall rules etc etc.
Currently I have to specify multiple IPv4 ranges in firewall rules in a messy way if I want to give AA access to something of mine. It's a lot easier with IPv6 as it's just one range to cover the whole ISP, and long may it remain so.
