IPv4 address

Internet Protocol version 4 (IPv4) is the fourth version of the (IP). It is one of the core protocols of standards-based internetworking methods in the Internet, and was the first version deployed for production in the ARPANET in 1983. It still routes most Internet traffic today, despite the ongoing deployment of a successor protocol, IPv6. IPv4 is described in IETF publication RFC 791 (September 1981), replacing an earlier definition (RFC 760, January 1980).

IPv4 is a connectionless protocol for use on packet-switched networks. It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. These aspects, including data integrity, are addressed by an transport protocol, such as the (TCP).

IPv4 uses 32-bit addresses which limits the address space to 4294967296 (2³²) addresses.

IPv4 reserves special address blocks for private networks (~18 million addresses) and multicast addresses (~270 million addresses).

IPv4 addresses may be represented in any notation expressing a 32-bit integer value. They are most often written in the dot-decimal notation, which consists of four octets of the address expressed individually in decimal numbers and separated by periods. The CIDR notation standard combines the address with its routing prefix in a compact format, in which the address is followed by a slash character (/) and the count of consecutive 1 bits in the routing prefix (subnet mask).

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