On 13/01/2013, at 20:51, Tony Langdon <vk3jed@gmail.com> wrote:
A /64 should do most home networks.
It should indeed. However, if you're using neighbour discovery (e.g., radvd in Linux) to deliver addresses to hosts, my understanding is that you need to use a /64 due to the way in which the host address is calculated - usually from the MAC address.
Of course, you don't have to do that, and then it is possible to divide a /64 (would have to use static addressing or DHCPv6)
the various ipv6 rfcs require a /64 for host subnets. you should ever further divide a /64, except in rare circumstances like point to point links. the rfcs also suggest a minimum of /56 per customer, and /48 for larger sites and provider-independent (PI) allocations. breaking up a /64 will cause problems for various technologies that expect the rfcs to be implemented properly. it's basically set up in ipv6 that the first 64 bits are entirely for routing, while the last 64 bits are entirely for hosts.