IPv4s

IPv4 refers to the fourth version of the Internet Protocol and denotes devices on a network with 32-bit addresses. In practice, addresses are written as four decimal octets in dotted notation, such as 192.0.2.1.

The IPv4 address space contains about 4.29 billion unique addresses. It includes public addresses assignable by regional registries, private addresses defined for internal networks (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), loopback (127.0.0.0/8), and link-local addresses (169.254.0.0/16). Several blocks are reserved for documentation and testing.

Subnetting and routing: Classful addressing grouped addresses into classes A, B, and C with default masks; this led to inefficient allocation. The introduction of Classless Inter-Domain Routing (CIDR) in the 1990s allowed flexible prefix lengths and improved route aggregation.

Private networks and NAT: To conserve global addresses, private addresses are not routable on the internet and are commonly translated to public addresses via Network Address Translation (NAT).

Current status and transition: Because the global IPv4 pool has been exhausted for new allocations, IPv4 remains widely used through NAT and address reuse. IPv6, a 128-bit protocol, provides a vastly larger address space and is gradually adopted to replace or coexist with IPv4 through transition mechanisms.

Impact and role: IPv4 remains foundational to the Internet, with ongoing management by regional Internet registries and service providers. While NAT and other techniques mitigate address scarcity, the long-term goal of full replacement is driven by the adoption of IPv6.