What is IPv6 6to4 tunnel address? 2022::/16 or 2002::/16? How do you convert the IPv4 address into IPv6 6to4 tunnel address? Well there is the long way, which you should understand and then there is the easy way in case you need to configure it really quickly. I found this nice method where you can use the IPv6 General Prefix feature to automatically calculate the conversion. Originally this feature was used to create a variable for IPv6 network, the “general-prefix”, to easily change all IPv6 addresses in case reassignment of IP subnets.