This time around we’ll learn about subnets and CIDR, hopefully in a more manageable manner than some books present it.
Let’s get one thing straight: there is no “Class” in subnetting. In the olden days, there were Class A, B and C networks. These could only be divided up into equal parts, so VLSM, or Variable Length Subnet Masks , were introduced. The old Class C was a /24, B was a /16, and A was a /8. (Check out Understanding IP Addresses if you’re not clear on what that means.) That’s all you need to know about Classes. They don’t exist anymore.