IPv4 Address

An IPv4 address is the fourth version of the Internet Protocol and the oldest widely used form of an IP address. It is a 32-bit number, written as four octets (bytes) separated by dots, where each octet takes a value from 0 to 255 — for example 192.0.2.15.

The structure of an IPv4 address

Thirty-two bits give a theoretical pool of about 4.3 billion unique addresses. An address is divided into a network part and a host part, and the boundary between them is set by the subnet mask (for example /24). The network part indicates which network a device belongs to, while the host part identifies the specific device within it. Some ranges are reserved: private addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) work only inside local networks, and 127.0.0.1 is the loopback address.

Because the pool of public IPv4 addresses is exhausted, the NAT mechanism is used widely — many devices on a local network share a single public address, and the router translates private addresses into the public one. The long-term answer to the shortage is the move to IPv6.

IPv4 addresses in practice

In hosting, an IPv4 address is stored in a domain's A record and points to the server that runs the site. A dedicated IPv4 address is sometimes required to configure certain SSL certificates, mail servers, or services that need a stable, exclusive address. When you launch a VPS, you usually receive a public IPv4 address that you configure in DNS, firewall rules, and service access logs. The address also appears in everyday diagnostics: ping and traceroute test host reachability and packet routes, while web server logs record each visitor's address for traffic analysis and abuse blocking.