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

IPv4 is a connectionless protocol for using packet-switched networks. It operates on a least-effort delivery model where it does not guarantee delivery, nor does it guarantee the correct sequence or avoid duplicate delivery. These aspects, including data integrity, are addressed by a higher layer of transport protocol, such as the Transmission Control Protocol (TCP).


IPv4 address in dotted-decimal notation

IPv4 uses 32-bit addresses, which limits the address space to 4 294 967 296 (2 32 ) addresses.

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

Address representations

IPv4 addresses can be represented in any notation by expressing a 32-bit integer value. They are most often written in dot-decimal notation, which consists of four octets of the address expressed individually in decimal and numbers separated by periods.

For example, the four-dotted IP address represents the 32-bit decimal version of the number 3221226219, which in hexadecimal format  is 0xC00002EB. It can also be expressed in dotted hexadecimal format, such as 0xC0.0x00.0x02.0xEB, or with byte values ​​such as 0300.0000.0002.0353.

CIDR notation combines the address with its routing prefix in a compact format, where the address is followed by a forward slash character (/) and the consecutive 1 -bit count of the routing prefix (subnet mask).

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