What Is IPv4 (Internet Protocol Version 4)?

Internet protocol version 4 (IPv4) is a widely used protocol that provides the foundation for internet communication. It is the fourth version of the internet protocol (IP) and has been in use since its introduction in 1983. IPv4 helps the routing and delivering data packets across interconnected networks, forming the basis for the modern internet infrastructure. 

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How do IPv4 addresses work?

IPv4 addresses are numerical identifiers assigned to devices connected to a network. The structure of an IPv4 address consists of two main components: the network address and the host address. The network address identifies the network to which a device belongs, while the host address distinguishes individual devices within that network. Subnets, created by using a netmask, define the division between the network and host portions of the address. This defines the size of the network and host segments.

IPv4 addresses are 32 bits long, typically expressed as a series of four decimal numbers separated by periods, such as in this address: 192.168.0.1. Each of the four numbers can range from 0 to 255, allowing for a total of approximately 4.3 billion unique addresses. 

Routers use IPv4 to forward data packets between networks. When a device sends data to another device on a different network, the data breaks into smaller packets, each containing the source and destination IPv4 addresses. Routers examine the destination address of each packet and use their routing tables to determine the appropriate path for delivery. The packets then forward from one router to another until they reach their destination.

Read more: Information Technology (IT) Terms: A to Z Glossary

IPv4 example

To illustrate, let's consider the example IPv4 address 182.153.0.1. In this case, the network portion of the address is 182.153.0, and the host portion is 1. The subnet mask associated with this address could be 255.255.255.0, indicating that the first three numbers (182.153.0) represent the network, and the last number (1) represents the host.

Address space in IPv4 vs. IPv6

IPv4 only offers limited address space. With approximately 4.3 billion unique addresses, IPv4 can’t keep up with the explosive growth of internet-connected devices, including computers, smartphones, IoT devices, and more. Internet protocol version 6 (IPv6) addresses this issue by offering a significantly larger address space and enhanced features.

However, the limited pool of available IPv4 addresses is now a problem due to the exponential growth of internet-connected devices. With fewer available IPv4 addresses, we need to adopt IPv6 to accommodate the growing number of online devices.

IPv6 uses 128-bit addresses, providing an enormous pool of unique addresses totaling approximately 340 undecillion (3.4 x 10^38). This allows each device to have a unique address, even as the number of internet-connected devices grows.

Related terms

• Internet protocol version 6 (IPv6) 

• Internet protocol (IP) address

• Transmission control protocol/internet protocol (TCP/IP)

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