What Is IPv4 (Internet Protocol Version 4)?

Internet Protocol (IP) addresses are essential to networks. Chances are your network uses IPv4, which is the most widely-integrated version of the IP address system thus far. In this article, learn what IPv4 is, how the IPv4 classes are structured, and the status of IPv4 compared to the new IPv6 in our modern Internet.

What is IPv4?

Internet Protocol version 4 (IPv4) is the fourth version of the IP address system. Each IPv4 address presents as a unique identifier formatted as a string of numbers. Each device connected to the Internet through the Internet of Things receives an IP address. An IP version 4 address, like any IP address, allows devices to communicate with each other on both internal and external networks.

IPv4 addresses are 32-bit integers expressed in hexadecimal notation or dotted decimal notation. This appears as x.x.x.x, where each x can value anywhere between 0 and 255.

It's essentially four octets separated by decimals; take, for example,, which is a valid private IP address. These addresses are typically assigned by a DHCP (Dynamic Host Configuration Protocol) serverrouter, or Internet service provider (ISP).

IPv4 address graphic

Understanding IPv4 classes

There are five classes of IPv4 addresses: class A, class B, class C, class D, and class E. IP providers reserve classes D and E for special use, meaning that the primary concern lies with classes A, B, and C. Each class has a different number of available addresses or host identifiers:

  • Class A, with over 16 million addresses
  • Class B, with 65,535 addresses
  • Class C, with 254 addresses

Each class has a designated IPv4 address range for public and private use.

Class A

Class A allows for the highest number of total hosts per network. For class A, network number values start at 1 and range to 127, with a private network range in between. The public IP range goes from to; the private IP range goes from to The class A subnet mask is

Class B

Class B provides the second highest number of total host addresses, with network number values starting immediately after class A at 128 and going to 191. These class B addresses typically are sufficient for medium-sized networks or some large networks. The public IP range for class B goes from to; the private IP range goes from to The class B subnet mask is

Class C

IPv4 class C addresses suffice for small local area networks, allowing up to 254 total hosts. Local network number values go from 192 to 223. The public IP range for class C goes from to; the private address range goes from to

Class C also has a special IP range; these addresses are loopback addresses, also known as the localhost. These unique IP addresses allow for your device to communicate with itself. The localhost IP address range is to Subsequently, the class C subnet mask is

Classes D and E

As mentioned above, classes D and E are not given to hosts. They each have different purposes. Class D addresses work for multicasting, which allows a single host to send streams of data to thousands of hosts across the Internet at once. They range from to

Networks use class E IPs only for research purposes, not for hosting, multicasting, or general use of any kind. They range from to

Classful network issues

Each existing network defines itself with one of the above categories depending on how many addresses it requires. This system worked well for years and allowed networks to access as many IP addresses as necessary. However, as the Internet grew and more devices per household required IP addresses, the classful system struggled.

The issue was that if an organization or computer network needed more than 254 addresses, for example, it would automatically push the network to class B. However, it didn't matter how many more addresses they needed. Whether it was 255 addresses or 65,000 addresses, it would go to class B. Therefore, it pushed many organizations into higher classes by only a few addresses, resulting in many wasted IPs as it reserved the rest of the addresses in that organization's block.

Situations like these depleted IP addresses unnecessarily fast, which became the issue with the IP version 4 addressing system. The Internet grew rapidly, but the IPv4 system couldn't provide the number of IPs needed for the future.

Is IPv4 still used today?

Though the classful addressing system is not faultless, IPv4 is still the dominant Internet protocol. It's the most integrated and widely-accepted version of IP address. Besides the eventual issue of running out of IPv4 addresses, there's nothing faulty about an IPv4 address in itself. Other solutions have been presented to solve the problem of IP address exhaustion - such as Classless Inter-Domain Routing (CIDR) and the new IPv6 system - but IPv4 addresses work in tandem with these solutions, meaning the IPv4 system still works for many users and devices.

What is the difference between IPv4 and IPv6?

Ultimately, there are no major differences between IP version 4 and IP version 6 that make one significantly better than the other. However, when comparing IPv4 vs. IPv6 system, they primarily differ in how they structure IP address size.

IP version 6 has 128-bit addressing space, an increase compared to IP version 4's 32-bit addressing space. The IPv6 address space has roughly 2128 or (3.4 x 1038) 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses available. To put it more simply, that's 340 trillion trillion trillion addresses.

IPv6 provides enhanced packet header for better routing compared to IPv4. Furthermore, mobile network devices receive better support and service with the IPv6 system.

IP version 4 supports broadcast IP addresses, whereas IP version 6 uses multicast addresses. Multicast addresses clarify identifiers for specific sets of interfaces belonging to various nodes. It supports host-inbound and host-outbound multicast traffic.

However, IPv6 addresses are not the standard yet; IPv4 addresses are still used most commonly. Therefore, unless you have a large network or one that needs greater support, an IPv4 IP address still works for your network.

Frequently asked questions

How many bits are in an IPv4 address?

There are 32 bits in an IPv4 address format, expressed in dotted decimal notation.

Should I use IPv4 or IPv6?

IPv6 is more advanced than version 4, but if you're on a small local network, either will serve your purposes.

Can two devices have the same IP?

On a single network, no, two devices cannot have the same IP. This will result in communication issues across the network, as IPs are meant to be unique identifiers for transmitting data.

How many IPv4 addresses are there?

Because of the 32 bits in IP version 4 addresses, there are four billion potential IPv4 addresses in existence.

What is an example of an IPv4 address?

Most people are familiar with private IP version 4 addresses, as their own network likely uses one. IPv4 address examples include,, and

What is my IPv4?

Users can check IP address on the WhatIsMyIP home page, though your IPv4 address varies by network.