6to4

6to4 is an address assignment and router-to-router automatic tunneling technology that is used to provide unicast IPv6 connectivity between IPv6 sites and hosts across the IPv4 Internet. 6to4 is described in RFC 3056. 6to4 uses the global address prefix:

2002:WWXX:YYZZ::/48

in which WWXX:YYZZ is the NLA ID portion of a global address and the colon hexadecimal representation of a public IPv4 address (w.x.y.z) assigned to a site. The full 6to4 address is:

2002:WWXX:YYZZ:[ SLA ID]:[Interface ID]

RFC 3056 defines the following terms:

• 6to4 host:A 6to4 host is any IPv6 host that is configured with at least one 6to4 address (a global address with the 2002::/16 prefix). 6to4 hosts do not require manual configuration and they create 6to4 addresses by using standard address autoconfiguration mechanisms.
• 6to4 router:A 6to4 router is an IPv6/IPv4 router that supports the use of a 6to4 tunnel interface and is typically used to forward 6to4-addressed traffic between the 6to4 hosts within a site and other 6to4 routers or 6to4 relay routers on an IPv4 network, such as the Internet. 6to4 routers require additional processing logic for proper encapsulation and decapsulation and might require additional manual configuration.
• 6to4 relay router:A 6to4 relay router is an IPv6/IPv4 router that forwards 6to4-addressed traffic between 6to4 routers on the Internet and hosts on the IPv6 Internet.