IPv6? No Problem, we’ll just use the same addressing plan as we do now!

(thanks to RIPE)

So, you are planning for IPv6? Have you thought about what you will do about the addressing? What’s the problem I hear, the addresses are the same except a lot longer?  Well yes and no. The addresses are a lot longer, but there is more.

While the IPv6 addressing structures are pretty similar to IPv4, there are also some differences which will need to be considered. These differences mean that you will likely have to create a whole new IPv6 design for your network. Like most technology problems, the earlier you start to think about them the more likely you will get a good outcome.

What do you need to consider? First, as I have written previously, there is not currently any standard NAT66 scheme. NAT66 may arrive, but when it does, expect version 1.0 to have issues. So one of your familiar tools may not be available when you are buildiong your new architecture.

Second, there is no exact analogue to the RFC1918 Private address space. RFC1918 addresses have been used extensively to minimise the impact of address depletion and to hide the internals of a network. There is a family of Unique Local addresses, which have some similar functionality, but they are not an exact replacement. The Unique Local addresses are slightly different in application.  Additionally, without NAT66, such an addressing plan would be difficult to implement.

There is also the issue that all devices generally use link local addresses for internal subnet communication, and a Unique Global address for off subnet comms, so all your devices will have at least 2 addresses, do you want to add the Unique Local addresses as well? Will

As well as the subnet planning, you will need to consider the impact of this change of addressing structure on your existing architecture, and how you will create a system in which the two address families can coexist and deliver the same level of service and security, without compromising the integrity of either.

Clearly, there is more to consider than a first glance would suggest. So as I suggested start planning early, the more planning space you can give yourself, the better chance of getting a smooth migration without unforeseen problems.

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