6 Replies Latest reply: Sep 13, 2011 8:55 AM by Yangk23 RSS



      I can't seem to subnet inside my head, and I always end up writting it down because I am a visual learner. I also use the Magic Number, 256. Any suggestions?

        • 1. Re: subnet
          Scott CCNA R&S, CCNA Security

          I used my fingers for a long time then stopped needing them.


          Left pinky = 128 subnet mask, 128 magic/block,  126 hosts, 2 subnets, prefix 25

          Left ring    = 192 subnet mask, 64 magic/block, 62 hosts, 4 subnets, prefix 26



          • 2. Re: subnet

            You can draw the table during exam to help you find Magic Numbers really quick


            Bit position >>
            Magic Number1286432168421
            Deciamal Mask128192224240248252254255
            Slash Notation for C class/25/26/27/28/29/30/31/32
            • 3. Re: subnet
              Ryan Lewis

              Writing it down is the best method!


              Especially if you understand it better, I could not find a good way to subnet for the longest time until I came across this at CLN which is just a reference. It sounds like you already have a method just practice and you'll get the pattern.



              I would not try to memorize everything keep it simple and write it down, less mistakes are done on paper because you visually see them.


              I Hope this Helps,


              • 4. Re: subnet

                I can just concur what everyone else is saying. Unfortunately this is one of those things that you just need to practice practice practice until it becomes easier. You will get to a point where it just clicks, and you will find it easier to do.


                I must admit, the easiest way of subnetting is the way taught by Jeremy Cioara who present the CBT Nuggets for CCNA. If you can get your hands on that nugget you will be well on your way!

                • 5. Re: subnet

                  pratice a lot in your head and see how you do when you write them down. If you got it down good in your head for the exam that will give you a lot of extra time in the long run to answer other questions.

                  you will get it soon

                  • 6. Re: subnet

                    I realize that if you know your x64, x32, x16, x8, and x4 multiplication table, you will have no problem.