ip address - Why is ARIN (etc.) allocating such large blocks of IPv6 addresses?

The whole issue of IPv4 depletion and waste seems to be finally getting behind us with the (somewhat) increased deployment of IPv6.

The sole purpose of IPv6 was to solve the issue of IPv4 address space running out. If that is the case then why are governing organisations allocating such large blocks of v6 addresses that are purely and utterly overkill and an obvious waste?

Is there logical reasoning behind the allocations or is it more of a case of a "I'm rich, Lets share them all around!" sort of thing?

For example, I was recently allocated a /48 block of v6 addresses with a single server. That's a staggering 1,208,925,819,614,629,174,706,176 addresses for my single server. I doubt the kernel would let me allocate that many addresses to an interface and I doubt any available NIC would support even a 10000th of them. Why are IPv6 addresses being handed out in such large blocks?

Answer

The main reason is that stateless address autoconfiguration as per RFC4862 requires a /64 network to work properly. Add to that the assumption that one will want more than a single subnet at one's installation and the difficulty of routing arbitrary multiples of a /64, and the automatic tendency seems to be to assign a /56, or if lazy, a /48.

Oddly, I'm already seeing the first signs of parsimony in the UK. I've had v6 in my home office for a couple of years, now, but recently changed provider. The old one gave me a /56 automatically; the new one gave me a /64, but when I mentioned that I was subnetting happily upgraded me to a /56 without charge.

My guess is that the base allocation will stabilise at a /64 once v6 becomes common, with anyone who has a half-decent reason for it getting a /56.