IPv6 address

An Internet Protocol Version 6 address (IPv6 address) is a numerical label that is used to identify a network interface of a computer or other network node participating in an IPv6 computer network.

An IP address serves the purpose of uniquely identifying an individual network interface of a host, locating it on the network, and thus permitting the routing of IP packets between hosts. For routing, IP addresses are present in fields of the packet header where they indicate source and destination of the packet.

IPv6 is the successor to the first addressing infrastructure of the Internet, (IPv4). In contrast to IPv4, which defined an IP address as a 32-bit value, IPv6 addresses have a size of 128 bits. Therefore, IPv6 has a vastly enlarged address space compared to IPv4.

IPv6 addresses are classified by the primary addressing and routing methodologies common in networking: unicast addressing, anycast addressing, and multicast addressing.

IPv6 does not implement broadcast addressing. Broadcast's traditional role is subsumed by multicast addressing to the all-nodes link-local multicast group ff02::1. However, the use of the all-nodes group is not recommended, and most IPv6 protocols use a dedicated link-local multicast group to avoid disturbing every interface in the network.

An IPv6 address consists of 128 bits. For each of the major addressing and routing methodologies, various address formats are recognized by logically dividing the 128 address bits into bit groups and establishing rules for associating the values of these bit groups with special addressing features.

Unicast and anycast addresses are typically composed of two logical parts: a 64-bit network prefix used for routing, and a 64-bit interface identifier used to identify a host's network interface.

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