IPv4 is the technology that allows computers to connect to the internet, whatever device we use. Each of these devices, in the instance that it connects to the internet, gets a unique code so that we can send and receive data with other connections.

As we already know, the IPv4 protocol transfers addresses that are 32 bits in length. With this type of architecture, it can manage approximately 4.3 billion IPs around the world, but the explosion of internet users in recent years has meant that the system is at its maximum capacity in regards to supporting more IP addresses.

The IPv4 address space is limited to 4.3 billion addresses. To obtain this number, we could decompose an IPv4 address as a 32-bit number consisting of four groups of 8 bits. In this way, we would have 256 different combinations to represent one IP address. This means that the possible values of an octet in an IP address would be in the range of 0 to 255.

To obtain the total number of IPv4 addresses, it would be enough to multiply 256 * 256 * 256 * 256, since an IPv4 address is composed of four sections with 256 possibilities in each section. In total, we would have 4, 294, 967, 296 addresses. In IPv4, the universe of addresses is divided into ranges or classes, as follows:

• CLASS A: 1.0.0.0-126.255.255.255
• CLASS B: 128.0.0.0-191.255.255.255
• CLASS C: 192.0.0.0-223.255.255.255
• CLASS D: 224.0.0.0-239.255.255.255 (Multicast)
• CLASS E: 240.0.0.0-254.255.255.255 (Experimental)

By definition, multicast and experimental addresses cannot be used as source addresses, so the previous number must be subtracted from 520, 093, 696. Within the different classes, we have network 0.0.0.0 (the identifier of all IPv4 networks), network 127.0.0.0 (used to identify physical loopbacks in network equipment), and network 255.0.0.0 (which includes the broadcast addresses of all networks). With these restrictions, 116, 777, 216 addresses must be removed from the total.

Due to this, the need to find a replacement was palpable, and it fell to the IPv6 protocol, the sixth revision of IP and the natural successor of IPv4, to create more addresses.