Subnetting Made Easy – Part 1: Decimal & Binary Numbers

We know decimal numbers. We’ve been using those all our lives, so we’re familiar with that. So, if you look at it, our number system is based on the value of where it sits:

1 1 1 1
1000 100 10 1
10^3 10^2 10^1 10^0

So this first column as we know is the ones column, then our tens, hundreds, and thousands. But really that’s ten to the zero, our ten to the 1 column, our ten squared column, and ten cubed, which means ten times ten times ten. So this is what we’re used to with decimal numbers, different positions have different values.

In binary numbers, it’s the exact same thing except instead of using base 10, we use base 2. Our values are 2 to the zero is one, then two to the one is two, two squared is four, then two times two times two is eight, that’s two cubed. Then two the fourth is 16, our next column is 32, then 64 and 128. This makes eight binary bits.


1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1

Your binary is 11010010

How to Determine the Size of a Network

So how do we determine the size of a network? The size of the network is determined by the number of host bits. The more host bits you have, the larger your network will be. If you have one host bits, it could either be a 0 or a 1. If you have two bits, it could be 00, 01, 10, or 11 so we have four combinations with two bits. So the size is equal to 2 to the number of host bits. That determines the size of our network.If we have one bit, it’s 21 or 2. If we have two bits it’s 22 or 4 possible combinations. If we have 8 host bits, it would be 28 which equals 256, and that would be the size of that network.

Guest Blogger: Jill Liles

In this article

Join the Conversation