6to4  is a router to router or host to router tunneling method where IPv6 packets are encapsulated in IPv4 packets.

Windows Vista and Windows 7 operating systems configure the 6to4 interface automatically if they have a routable IPv4 address and they do not have IPv6 connection. Automatic configuration uses the anycast address  to which the closest 6to4 Relay Router answers.

Windows XP operating system should have IPv6 support installed in order to get the 6to4 interface configured. The command for Windows operating systems to set the 6to4 relay router as the closest 6to4 relay router is given below.

netsh int ipv6 6to4 set relay