Simple Binary Graphical Subnetting

When I first heard about this method, the title scared me: BINARY - yikes! Having taught Cisco networking curriculum for a number of years, I had visions of complex binary math running through my head - I was WRONG! There is minimal binary math involved and the method is very straight forward.

There are some significant advantages to using this graphical method:

  • The subnetting is graphical and you can visually see how your network is subnetted
  • It lends itself quite easily to complex subnetting problems.
  • The traditional boundaries of Class A, B and C don't really matter
  • Route summarization is incredibly easy to do.
  • Re-assigning subnets to different address spaces in the network is easily accomplished.

This is a simple Class C subnetted with 4 subnets example. Templates/worksheets for this example are available here

The following webpages step you through a more complicated Class C subnetted network consisting of 8 subnets. The Simple Binary Graphical Subnet method consists of six parts, performed in this order:

  1. The Basic Numbers Chart - if you are familiar with the Magic Chart from the How to make the Network Class Chart for dummies, you will see that we've just turned it 90 degrees sideways. This is the first step in the Simple Binary Graphical Subnet method. Have to do this first before creating the Grapical Subnet Chart.
  2. The Graphical Subnet Chart - This is the address map where the subnets are plotted. It gives you the visual address space of the network that you are subnetting. This is the second step, you need to have the Basic Numbers Chart on hand in order to create this Chart
  3. The Network Address Map - After creating the Graphical Subnet Map, you prepare for the subnets, number of hosts required, subnet masks and prefix.
  4. The Map the Graphical Subnet Chart - This is where the visual part comes in. We fill in the Graphical Subnet Chart with each of the subnets that were prepared out with the Graphical Subnet Map from which we can determine the Subnet addresses.
  5. The Calculate the Broadcast Address - Now you can easily determine the broadcast addresses for each subnet.
  6. The Calculate the Hosts - By knowing the subnet addresses and their broadcast addresses, we can easily determine the host range. This is the last step.

Note: There are no official names for the three parts. I made up those names as we needed something to refer them to during the following explanations.

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Copyright July 2013 Eugene Blanchard