Comments:"IPv6 address space layout best practices - Network Engineering Stack Exchange"
URL:http://networkengineering.stackexchange.com/q/119/231
With IPv6 you no longer have to worry about allocating space for a given number of hosts. All subnets (other than P2P links) should be assigned as a /64 which gives you a ridiculous number of host addresses. This frees you to focus on other topics such as good network layout & design. (A /48 would give you 65,536 /64 networks)
There are (of course) several schools of thought on this. If you are already pretty happy with your IPv4 design, then doing a IPv6 overlay that mirrors things is probably a good option and eases the transition for everyone.
- 2001:0DB8:1:1:: /64 --> 10.1.1.0 /24
- 2001:0DB8:1:2:: /64 --> 10.1.2.0 /24
- ...
- 2001:0DB8:1:254:: /64 --> 10.1.254.0 /24
Play around with some of the IPv6 calculators to help you get your head around all of this. Here is an example one: GestioIP Online IPv4/v6 Calculator
This was the hardest thing for me to get over - don't worry about allocating space for hosts! Plan your network -- focus on locations of layer-3 boundaries, services offered, physical location of devices, etc. It is probably going to be years before you have a pure IPv6 network, but you will begin laying the groundwork of good network design now.