Special IPv6 Addresses

The following are the special IPv6 addresses:

Unspecified address

The unspecified address (0:0:0:0:0:0:0:0 or ::) is used only to indicate the absence of an address. It is equivalent to the IPv4 unspecified address of 0.0.0.0. The unspecified address is typically used as a source address when a unique address has not yet been determined. The unspecified address is never assigned to an interface or used as a destination address.

Loopback address

The loopback address (0:0:0:0:0:0:0:1 or ::1) is assigned to a loopback interface, enabling a node to send packets to itself. It is equivalent to the IPv4 loopback address of 127.0.0.1. Packets addressed to the loopback address must never be sent on a link or forwarded by an IPv6 router.

Transition Addresses

To aid in the transition from IPv4 to IPv6 and the coexistence of both types of hosts, 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 with IPv6 over an IPv4 infrastructure that uses public IPv4 addresses, such as the Internet. IPv4-compatible addresses are deprecated in RFC 4291 and are not supported in IPv6 for Windows Vista and Windows Server 2008.

IPv4-mapped address

The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF: w.x.y.z, is used to represent an IPv4 address as a 128-bit IPv6 address.

6 to 4 address

An address of the type 2002:WWXX:YYZZ:Subnet ID:Interface ID, where WWXX:YYZZ is the colon hexadecimal representation of w.x.y.z (a public IPv4 address), is assigned a node for the 6to4 IPv6 transition technology.

ISATAP address

An address of the type 64-bit prefix:0:5EFE:w.x.y.z, where w.x.y.z is a private IPv4 address, is assigned to a node for the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) IPv6 transition technology.

Teredo address

A global address that uses the prefix 2001::/32 and is assigned to a node for the Teredo IPv6 transition technology. Beyond the first 32 bits, Teredo addresses are used to encode the IPv4 address of a Teredo server, flags, and an obscured version of a Teredo client’s external address and UDP port number.

IPv4 Addresses and their corresponding IPv6

IPv4 Address	IPv6 Address
Internet address classes	Not applicable in IPv6
Multicast addresses (224.0.0.0/4)	IPv6 multicast addresses (FF00::/8)
Broadcast addresses	Not applicable in IPv6
Unspecified address is 0.0.0.0	Unspecified address is ::
Loopback address is 127.0.0.1	Loopback address is ::1
Public IP addresses	Aggregatable global unicast addresses
Private IP addresses (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16)	Site-local addresses (FEC0::/48)
APIPA addresses (169.254.0.0/16)	Link-local addresses (FE80::/64)
Text representation: Dotted decimal notation	Text representation: Colon hexadecimal format with suppression of leading zeros and zero compression. IPv4-compatible addresses are expressed in dotted decimal notation.
Network bits representation: Subnet mask in dotted decimal notation or prefix length	Network bits representation: Prefix length notation only

Assigning IPv6 address to Devices

IPv6 Addresses for a Host

An IPv4 host with a single network adapter typically has a single IPv4 address assigned to that adapter. An IPv6 host, however, usually has multiple IPv6 addresses assigned to each adapter. The interfaces on a typical IPv6 host are assigned the following unicast addresses:

• A link-local address for each interface
• Additional unicast addresses for each interface (which could be one or multiple unique local or global addresses)
• The loopback address (::1) for the loopback interface Typical IPv6 hosts are always logically multi homed because they always have at least two addresses with which they can receive packets—a link-local address for local link traffic and a routable unique local or global address. Additionally, each interface on an IPv6 host is listening for traffic on the following multicast addresses:
• The interface-local scope all-nodes multicast address (FF01::1)
• The link-local scope all-nodes multicast address (FF02::1)
• The solicited-node address for each unicast address assigned
• The multicast addresses of joined groups

IPv6 Addresses for a Router

The interfaces on an IPv6 router are assigned the following unicast addresses:

• A link-local address for each interface
• Additional unicast addresses for each interface (which could be one or multiple unique local or global addresses)
• The loopback address (::1) for the loopback interface
• Additionally, the interfaces of an IPv6 router are assigned the following anycast addresses:
• A Subnet-Router anycast address for each subnet
• Additional anycast addresses (optional)
• Additionally, the interfaces of an IPv6 router are listening for traffic on the following multicast addresses:
• The interface-local scope all-nodes multicast address (FF01::1)
• The interface-local scope all-routers multicast address (FF01::2)
• The link-local scope all-nodes multicast address (FF02::1)
• The link-local scope all-routers multicast address (FF02::2)
• The site-local scope all-routers multicast address (FF05::2)
• The solicited-node address for each unicast address assigned
• The multicast addresses of joined groups