Subnetting Demystified
Here is a set of videos that cover subnetting. This series, by Bosen software, covers CIDR notation, Address Classes, Binary math, IP Addressing, and reasons for subnetting. Bosen offers practice exams for various IT certification exams.
Introduction (Part 1)
IP Addressing
Binary Math
Address Classes
CIDR Notation
Why Subnet?
Subnetting How To
Subnetting a Class B (1)
Subnetting a Class B (2)