Subnetting for Complete Idiots: Part I

Little-professor-1Let me first start off by saying that I do not actually think that I am a complete idiot, however it being educated by the Georgia Public School system I can safely say that there are a few subjects where my knowledge is lacking. Specifically mathematics. Honestly everything else that you might have missed learning in high school you can pretty much pick up along the way just by picking up a book or through a bit of on the job training. But not math — its just one of those things that you are never going to find yourself learning for fun.


Now why are we talking about mathematics? Because we are about to jump face first into Subnetting. But instead of attempting to cram every bit of it in our brains in one sitting, we are going to sit back and take our time and learn it step by step. As a matter of fact we are not even really going to talk about subnetting today. Rather we are just going to talk a bit about binary math.


Now, I'm not about to write an article explaining binary or base-2 number systems, no there are plenty of articles our there that explain it. Here and here are a couple.

What I am going to show you is this little table, which you need to memorize.




You need to memorize 20 through 27th. You need to know that if you add up sum of 20 to 27th it equals 256. You need to memorize.


Why is this important – well if you recall an IP address is 32 bits in lenght and is made up for 4 seperate octets. The chart above represents an octet with the maxiumim number possible being 256 and the minimum being one.

Note that this is where we are going to stop for today — all you need to walk away with is an understanding of how the chart above relates to an octet of a IP address.


Related articles

Subnets and prefixes
Understanding and performing IPv4 subnetting
Calculating the number of bits in a Subnet Mask in C#
Netting the concept of subnets