Unlike IPv4, where you always needed to use subnets to help manage routing, subnetting is optional in an IPv6 LAN. I've often seen them used for management purposes. For example, you can set up all of Building 4 in one subnet and all of Accounting in another, and so on.
Broadly speaking there are three kinds of IPv6 addresses:
1. Unicast addresses A Unicast address acts as an identifier for a single interface. This is the equivalent to the IPv4 address your computer is using at this very moment to identify itself as a unique PC on your local network. The point of Unicast is to make it easier to manage Internet addressing and routing.
2. Multicast addresses A Multicast address acts as an identifier for multiple network interfaces even if they belong to different nodes. So, for instance, any IPv6 packet sent to the Multicast address: FF02:0:0:0:0:0:0:2 is sent to all routers on the local network. Multicast is most commonly used for sending signals to a given group of systems or for broadcasting video or audio to multiple computers at once.
3. Anycast addresses In Anycast, a packet is delivered to the nearest, in terms of routing distance, of multiple interfaces. So, for instance, if you sent out a packet to an anycast address, your router or switch will send it to the closest possible device.
Implementing IPv6 in your office
So that's all well and good, but what do you need to do to start using IPv6? Well, on your PCs, you might not need to do anything. Windows, starting with Vista, turned IPv6 on by default. Windows didn't do anything with it mind you, but it was on.
I can't think of a single significant desktop operating system that doesn't have IPv6 support baked in. Mac OS X and Linux. The same is true of server operating systems: Windows Server 2008; Solaris, Red Hat Enterprise Linux (RHEL), Ubuntu and all the others.
The real trick is getting network equipment that supports IPv6. That may sound odd. I certainly find it so. While enterprise level network switches, such as the Cisco Catalyst series and Juniper Networks EX Series switches do a fine job of supporting IPv6, small business and home products often don't support it or do a lousy job of it.
If you're running a small business or want to get ahead of the IPv6 curve at home, do not assume that the switches and routers in your price range will have IPv6. Check. Then, even if the company states that it does, I hate to say this, but you're going to need to check again by trying it out.
I've found much so-called IPv6 compliant equipment really wasn't when push came to shove.
Making the IPv6 Internet connection
OK, your PCs, servers, and what-have-you are all running IPv6 and you want to connect to the IPv6 Internet, now what?