What Is IPv4 (Internet Protocol Version 4)?

Key takeaways

• Internet protocol version 4 (IPv4) is a widely used protocol that provides the foundation for internet communication.

• IPv4 addresses are only 32 bits long, resulting in a finite number of 4.3 billion unique addresses for devices to use, with the number dwindling; IPv6 addresses are 128 bits long, totaling 340 undecillion.

• The IPv4 address allows routers to forward data packets between networks efficiently and accurately.

IPv4 addresses use a subnet mask to allow systems to decode the network and host portions of the address. Discover more about IPv4, how it works, and how it compares to IPv6.

Learn in-demand IT skills from a tech industry leader by enrolling in the Microsoft IT Support Specialist Professional Certificate program. In just three months, you can learn to apply concepts like data management, troubleshooting, customer support, and networking while earning an employer-recognized certificate from Microsoft.

What is an IPv4 network, and how does it 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 is broken 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 are then forwarded from one router to another until they reach their destination.

What is an example of an IPv4 address?

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 a 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 IPv4 addresses available, 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.

Read more: Understanding IPv4 vs. IPv6

How to identify IPv4 and IPv6?

An IPv4 address always has four octets and three periods: (x. x. x. x) with the octet value being any one between 0 and 255. A valid IPv4 address could look like: 192.168.1.0.

An IPv6 address uses eight segments that contain any hexadecimal value from 0000 to FFFF and is separated by colons, unlike the periods of IPv4: (y: y: y: y: y: y: y: y). An example of a valid IPv6 could look like: 85ad: 5e3f: e89b: e217: f691: cc12: 4a77: 486b.

Related terms

• Internet protocol version 6 (IPv6)

• Internet protocol (IP) address

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

Explore our free resources for IT networking

If you’re interested in expert guidance and no-fluff tips to help you build your skills, subscribe to our Career Chat newsletter. You can also explore free career resources to learn new topics, explore emerging industries, and discover new opportunities:

• Bookmark for reference: Information Technology (IT) Terms: A to Z Glossary | Coursera

• Continue learning: Cybersecurity Learning Roadmap: Beginner to Expert

• Watch on YouTube: CCNA vs. Network+: Decoding Your Networking Certification Path

Accelerate your career growth with a Coursera Plus subscription. When you enroll in either the monthly or annual option, you’ll get access to over 10,000 courses.