IPv6 address types

Prefix Designation IPv4 equivalent
::/128 Unspecified
This address may only be used as a source address by an initializing host before it has learned its own addresses.
::1/128 Loopback
This address is used when a host talks to itself over IPv6. This often happens when one program sends data to another.

Example: ::ffff:

Used to embed IPv4 addresses in an IPv6 address. One use for this is in a dual-stack transition scenario where IPv4 addresses can be mapped into an IPv6 address. See RFC 4038 for more details.
No IPv4 equivalent. However, you can search for the mapped IPv4 address in the relevant Whois Database.

Example: fdf8:f535:82e4::53

Unique Local Addresses (ULAs)
Reserved for local use in home and enterprise environments (not public address space).
Private, or RFC 1918 address space:


Example: fe80::200:5aee:feaa:20a2

Link-Local Addresses

Used on a single link or a non-routed common access network, such as an Ethernet LAN. They do not need to be unique outside of that link.

May appear as the source or destination of an IPv6 packet. Routers must not forward IPv6 packets if the source or destination contains a link-local address.

Example: 2001:0000:4136:e378:8000:

This is a mapped address allowing IPv6 tunnelling through IPv4 NATs. The address is formed using the Teredo prefix, the server’s unique IPv4 address, flags describing the type of NAT, the obscured client port, and the client IPv4 address, which is usually a private address. It is possible to reverse the process and identify the IPv4 address of the relay server, which can then be looked up in the relevant Whois Database.
No IPv4 equivalent

Example: 2001:0002:6c:ab::a

Reserved for use in documentation. They should not be used as source or destination addresses.

Example: 2002:cb0a:3cdd:1::1

A 6to4 gateway adds its IPv4 address to this 2002::/16, creating a unique /48 prefix. As the IPv4 address of the gateway router is used to compose the IPv6 prefix, it is possible to reverse the process and identify the IPv4 address, which can then be looked up in the relevant Whois Database.

See how it works on Potaroo.

There is no IPv4 equivalent, but has been reserved as the 6to4 relay anycast address prefix by the IETF.

Example: 2001:db8:8:4::2

used in examples and documentation. These should never be source or destination addresses.
2000::/3 Global Unicast
The operators of networks using these addresses can be found using the RIR Whois servers listed in the IANA registry.
No equivalent single IPv4 block

Example: ff01:0:0:0:0:0:0:2

Used to identify multicast groups. They should only be used as destination addresses, never as source addresses.