Even though the original IP addressing scheme was relatively simple, it has become complex over time as changes have been made to it to allow it to deal with various addressing requirements. The more advanced styles of IP addressing, such as subnetting and classless addressing, are the ones used most in modern networks. However, they can be a bit confusing to understand. To help make sense of them we must start at the beginning with a discussion of the fundamentals of IP addressing.

In this section I begin our larger exploration of IP addressing by explaining the key concepts and issues behind it. I begin with an overview of IP addressing and discussion of what it is all about in general terms. I describe the size of IP addresses, the concept of its “address space” and the notation usually used for IP addresses. I provide basic information on the structure of an IP address and how it is divided into a network identifier and host identifier. I then describe the different types of IP addresses and the additional information such as a subnet mask and default gateway that often accompanies an IP address on larger networks. I provide a brief description of how multiple addresses are sometimes assigned to single devices and why. I conclude with a description of the process by which public IP addresses are registered and managed, and the organizations that do this work for the global Internet.