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One of the most intimidating but extremely important subjects on the CCENT/CCNA or ICND1 exam is subnetting. We were all taught to think in decimal but computers think in binary and the idea of all those ones and zeros are just a bit overwhelming for most of us. A subnetwork, or subnet, is a subdivision of an IP network address providing multiple smaller networks. Subnetting is the practice of dividing a network IP address into two or more networks.

There are a number of excellent tools available online as well as computer applications to make this task easy and I believe that you should be allowed to use these on the exam, let’s face it if you are configuring a router or switch you are going to have access to a computer, but like grade school students calculators are not allowed on the exam. Therefor we must learn to subnet in our heads or wood brain as it were. Due to a time limit on the exam you do not have a lot of time for wood brain; you need to answer these questions in about 30 sec.

There are a number of methods available to master this subject. There are decimal and binary methods; there is even a Magic Number method it just depends on which method work best for you. Myself I like to spend some time before starting the exam and create a subnet cheat chart. You are not allowed to bring anything with you to an exam but you can request blank paper and a pencil. This chart is easy to create on the fly if you can multiply by 2, just keep doubling the previous number starting with 4 then for the subnet mask subtract the number you are doubling from the previous sub net mask starting with 252 example (252 – 4 = 248).

Now that you see how this chart is created try creating it on your own without referring to this example. Use it to practice subnetting also try this Subnetting Game from the Cisco Learning Center using your chart and see how you do.

4 Responses to “Learn to Subnet Using Games and Charts”

1. dsln9138 Says:
   January 21st, 2013 at 11:03 am

   I can’t fing the subnetting game

2. admin Says:
   February 10th, 2013 at 11:07 am

   The link is in the article but here it is again, https://learningnetwork.cisco.com/docs/DOC-1802

3. pcedron Says:
   February 26th, 2013 at 2:59 pm

   First time here… so far, so good

4. mark_praktisero Says:
   March 21st, 2013 at 4:45 am

   tnx

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