Transition mechanisms facilitate IPv6 integration by enabling IPv4 and IPv6 to coexist in situations where full native IPv6 is not yet possible. Fundamentally, transition mechanisms let you remove or temporarily avoid the constraints often placed on IPv6 deployment by the existing infrastructure. They allow you to decouple your IPv6 rollout schedule from the IPv6 readiness of the environment.
As the term transition implies, these mechanisms are not to be used in the long term. Your main goal is to run an IPv6-only network, meaning that the end-state network would have neither IPv4 enabled nor any transition mechanisms left in the network. An IPv6-only network will be much easier to manage and secure, and much more efficient in routing and administration. But since in most cases you cannot deploy native IPv6 in one big step, transition mechanisms support a phased integration to reach that end goal—they are only to be used temporarily until you can turn on native IPv6. And because IPv4 will coexist with IPv6 for a long time, I prefer to instead call them integration mechanisms, as they help you get IPv6 deployed while you’re still running IPv4.
There is a large and growing number of integration mechanisms. They can be classified as follows:
From the 50,000-foot view, this is also the preferred order of leveraging these mechanisms. Since nobody will have ...