The two main programming tasks associated with IPv6 exploitation involve migrating existing application programs to support IPv6 and designing new programs for IPv6. In both cases, the changed or new code should be designed so that it is capable of using IPv4 or IPv6 addresses. Servers should be designed so that they can communicate with both IPv4 and IPv6 clients. Existing IPv4 client and server programs should continue to operate properly as long as only IPv4 connectivity is required between clients and servers.

The following topics describe key differences between IPv4 and IPv6.