Hello Dave, IPv6 was developed as a substitute/replacement for IPv4. Therefore it was not natively designed to be able to convert between the two. Now there ARE ways (using NAT, Network Address Translation) and other advanced features to swap an IPv4 header (including addresses) for an IPv6 header and vice-versa but there is no consistent/standardized way to do it. Various NAT-related features can translate from one address to another but they do it using different methods. At the CCNA and CCNP level, you are expected to know that if a device has an IPv4 address...it will send IPv4 packets (end-to-end) to the destination station. If it has an IPv6 address, it will send IPv6 packets (end-to-end) to the destination station. Only in cases where an IPv4 (only) station needs to communicate with an IPv6 (only) station do addresses need to be translated. However, where I do briefly talk about a couple of these techniques are in the CCNP Routing & Switching Technologies v2 series:Overview of IPv6 Tunneling Options and NAT-PT ISATAP Tunnels Hope that helped!