IPv4adress

IPv4adress, commonly referred to as an IPv4 address, is a 32‑bit numeric label assigned to devices participating in an IPv4 network. It serves to identify a host or other endpoint and to facilitate routing of packets across interconnected networks. IPv4 addresses are usually written in dotted decimal notation as four decimal numbers between 0 and 255, separated by periods, for example 192.0.2.1. The address space provides about 4.29 billion unique addresses.

The 32 bits are interpreted as a network prefix and a host identifier, the boundary between which is defined by a subnet mask or a CIDR prefix length, such as 192.0.2.0/24. Historically, addresses were organized by classful addressing into A (/8), B (/16), and C (/24) networks, but this scheme has been superseded by CIDR. Private addresses defined in RFC 1918 are not globally routable and are commonly used inside private networks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Public addresses are globally routable on the Internet. Special-purpose addresses include loopback 127.0.0.0/8, link-local 169.254.0.0/16, and the limited broadcast 255.255.255.255. 0.0.0.0 represents an unspecified address, and 255.255.255.255 is a broadcast address in some contexts.

IPv4adress addresses are allocated and managed by regional Internet registries (RIRs) such as ARIN, RIPE NCC, APNIC, AFRINIC, and LACNIC, under policies coordinated by the Internet Assigned Numbers Authority (IANA). As demand for addresses grew, network operators adopted Network Address Translation (NAT) to permit multiple devices to share a single public address. This, along with more efficient allocation, contributed to IPv4 exhaustion and accelerated the development and deployment of IPv6, the successor protocol designed with a vastly larger address space.

IPv4adress are used by transport-layer protocols such as TCP and UDP to deliver data to the intended endpoint and are a foundational element of routing and network configuration. Despite ongoing IPv6 rollout, IPv4 remains widely used and is expected to coexist with IPv6 for the foreseeable future.