Appendix B. Converting IP Addresses Between Decimal and Binary

As mentioned in Chapter 10, "Delivering the Goods to the Right Street (IP) Address," IP addresses are 32-bit binary numbers, but they are also frequently written and seen as decimal numbers. Although you could read Chapter 10 without thinking about IP addresses in their binary format, if you decide to read further to gain more knowledge about IP and IP addressing, you need to understand binary decimal, and how to convert numbers between each format.

Many of the books that tell you more about IP addressing and subnetting don't really tell you how to do the math to convert the numbers. Often, they suggest that you use a calculator or use a conversion chart like the one shown later in this appendix. Both of those options are reasonable. However, to prepare you for the future, if you decide to learn even more about IP, this appendix gives you the basics of decimal and binary conversion, including how to convert IP addresses between the two types of numbers.

This appendix includes three main sections. The first section explains decimal and binary numbering. The second section describes how to convert numbers from decimal to binary, and vice versa. Finally, the third section closes with some details of how to convert decimal and binary IP addresses to the other numbering system.