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IPv6 and IPv4 Co-existence


t would have been so easy if the early Internet and TCP/IP network designers had made IPv6 backward compatible with IPv4. They didn’t. And, while Leslie Daigle, Chief Internet Technology Officer for the Internet Society, admitted at a June 2009 meeting that IPv6’s “lack of real backwards compatibility for IPv4 was [its] single critical failure,” crying over spilt standards isn’t going to help us now. No, instead we have to make the best of using IPv6 in an IPv4 world.

How? It depends on what your network and operating system vendors offer. You may not know it, but almost all vendors already have a variety of solutions in place. You must — I can’t emphasis this enough — must test IPv6-to-IPv4 component interoperability before deploying them. Let’s take a look at the options.

IPv4/IPv6 approaches usually take one of two forms. One is dual stack, where your network hardware ends up running IPv4 and IPv6 at the same time. The other is to “tunnel” one protocol within another. Usually, this means taking IPv6 packets and encapsulating them in IPv4 packets. Their technical basics are outlined in the RFC 4213 Basic Transition Mechanisms for IPv6 Hosts and Routers.

There are other methods as well. For example, there’s Network Address Translation – Protocol Translation (NAT-PT). Like the name says, in this method an additional device translates IPv6 packets into IPv4 packets.

Dual-stacking and tunneling are going to be your main choices. Both come with advantages and disadvantages.

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