IP Subnetting using CIDR notation
By far this is the part of networking that scares students. However, it is not that scary. You just need to understand binary math. Oops I guess that is the scary part. Well not any more. Here are some tips and trick to make it easy.
A great book on the topic is "IP Subnetting made Easy!: A very simple and very clear guide to understanding IP subnetting that won’t leave you pulling your hair out." by John Kowalski. It is only $2.99 for Amazon kindle format.