Compatibility Addresses

Compatibility Addresses
To aid in the transition from IPv4 to IPv6, the following addresses are defined:
• IPv4-compatible address
The IPv4-compatible address, 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z (where w.x.y.z is the dotted decimal representation of a public IPv4 address), is used by IPv6/IPv4 nodes that are communicating using IPv6. IPv6/IPv4 nodes are nodes with both IPv4 and IPv6 protocols. When the IPv4-compatible address is used as an IPv6 destination, the IPv6 traffic is automatically encapsulated with an IPv4 header and sent to the destination using the IPv4 infrastructure. IPv6 for Windows Server 2003 and Windows XP supports IPv4-compatible addresses, but they are disabled by default.
• IPv4-mapped address
The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, represents an IPv4-only node to an IPv6 node. IPv4-mapped addresses are used for internal representation only. The IPv4-mapped address is never used as a source or destination address of an IPv6 packet. IPv6 for Windows Server 2003 and Windows XP does not support IPv4-mapped addresses.
• 6to4 address
The 6to4 address is used for communicating between two nodes running both IPv4 and IPv6 over the Internet. You form the 6to4 address by combining the global prefix 2002::/16 with the 32 bits of a public IPv4 address of the node, forming a 48-bit prefix. 6to4 is an IPv6 transition technology described in RFC 3056.
• ISATAP address
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) defines ISATAP addresses used between two nodes running both IPv4 and IPv6 over a private intranet. ISATAP addresses use the locally administered interface ID ::0:5EFE:w.x.y.z in which w.x.y.z is any unicast IPv4 address, public or private. You can combine the ISATAP interface ID with any 64-bit prefix that is valid for IPv6 unicast addresses, including the link-local address prefix (FE80::/64), site-local prefixes, and global prefixes. ISATAP is an IPv6 transition technology described in RFC 4214.
• Teredo address
The Teredo address is used for communicating between two nodes running both IPv4 and IPv6 over the Internet when one or both of the endpoints are located behind an IPv4 network address translation (NAT) device. You form the Teredo address by combining the 2001::/32 Teredo prefix with the public IPv4 address of a Teredo server and other elements. Teredo is an IPv6 transition technology described in RFC 4380