Introduction: The Rigid Past and the Flexible Future

In the early days of the internet, things were simpler. There were only a few hundred computers, and we didn't think we would ever run out of room. This led to a system called Classful Addressing. But as the internet exploded, we realized we needed something smarter. We needed Classless Addressing.

In this guide, we'll look at the differences between these two systems and how the move to 'Classless' saved the internet from running out of space in the 90s.

The Classful Era (Class A, B, and C)

Before 1993, IP addresses were divided into three main 'sizes' or classes:

Class A: For massive companies. One block gave you 16 million addresses.
Class B: For medium companies. One block gave you 65,000 addresses.
Class C: For small companies. One block gave you 256 addresses.

The problem? If you needed 300 addresses, a Class C wasn't enough, but a Class B was far too much, wasting tens of thousands of addresses.

The Classless Revolution (CIDR)

In 1993, CIDR (Classless Inter-Domain Routing) was introduced. It removed the rigid boundaries. Instead of 'Classes', you could define a network of exactly the size you needed (e.g., 512, 1024, or 2048 addresses). This slowed down the exhaustion of IPv4 addresses significantly.

Conclusion

Classless addressing is the reason the modern internet can scale to billions of devices. It provides the surgical precision we need to manage the web's geography. Check your address here.