One of the most difficult aspects for many people to understand about TCP/IP networking is subnetting. Our friend George Ou wrote an outstanding piece on the subject a while back, and we highly recommend it if you’re looking to get a full understanding of this area.
IP subnetting is a fundamental subject that's critical for any IP network engineer to understand, yet students have traditionally had a difficult time grasping it. Over the years, I've watched students needlessly struggle through school and in practice when dealing with subnetting because it was never explained to them in an easy-to-understand way. I've helped countless individuals learn what subnetting is all about using my own graphical approach and calculator shortcuts, and I've put all that experience into this article.