subnetting: how fast is fast

hoboscratchhoboscratch Member Posts: 11 ■□□□□□□□□□
I've been lurking on these forums for a while as I've found quite a few posts helpful in my self study for the ccna. I'll be taking the test in about 30 days and have seen a lot of people mention "subnet in your head" and "be able to subnet fast" etc etc.

I can subnet in my head provided I have a pencil and paper to note stuff down but I'm curious as to what is considered fast to most people.

Just interested to see where I'm at on this part and if I need to practice more or can comfortably move on.



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    Ed RooneyEd Rooney Member Posts: 52 ■■□□□□□□□□
    You get to a point where you can just see the block. It also helps to have a few of the slash notations memorized so that you can drop by eights, ie, a /20 is the same as a /28, just in a different octet. If you do it enough and have a system, it shouldn't take more than 5-10 seconds to find all of the pertinent addresses. In practice exams I tend to start typing in the IP address while I'm figuring out the answer.

    When I first did my MCSE-TCP/IP test in 1999 and CCNA in 2000 I just memorized the subnetting chart and wrote it on the scrap paper in the test room. Then I kind of stumbled on the block method. Most of the networks I worked with were /24 and /30. It didn't take long to figure out the relationship between the block size and the mask. I never realized that someone else did it that way until I started working on my recert and bought Lammle's book a month ago.
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    hoboscratchhoboscratch Member Posts: 11 ■□□□□□□□□□
    right on. yeah i'm not that fast but i'm getting down under 30 sec regularly. even in the last 90 min i've realized a few shortcuts that have helped eliminate the pencil on quite a few questions. thanks, now i have something to shoot for instead of an adjective relative to someone's perception.
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    KaminskyKaminsky Member Posts: 1,235
    On subnettingquestions I am typically hitting < 10 seconds on the simpler ones with the tougher ones taking upto 30-40 seconds.

    Of course it's not a speed contest and I am not particularly gifted at mental arithmetic, but thats just how quick it can get naturally when you get comfortable with your method. As subnetting seems to becoming just a part of larger questions, time saved here can pay dividends later on.

    Just keep hitting subnettingquestions.com for practice, practice and practice and if you get one wrong, work out why instead of just clicking next.

    Eventually it's like, "Well ! don't know what I was fussing about with this... it's simple!" which is quite a nice feeling after all the grief you go through to get this down. :D
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    lauplaup Member Posts: 9 ■□□□□□□□□□
    Rules as follows the more u do it, the easier it becomes. so test yourself more and it will become second nature.
    But dont brag about it down the pub it wont do u any favours :P
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    LearnAsIGoLearnAsIGo Member Posts: 20 ■□□□□□□□□□
    As recommended by others, I go to subnettingquestions.com almost daily.

    Then I just keep running through the questions until I can "feel the flow," so to speak.

    If I practice at the site for about 30 minutes, then I sorta kinda "see" how Ed Rooney views the block.

    But I haven't reached the point where I can come up with the answer while I'm typing the IP address

    - that's pretty cool, Ed. Maybe soon I'll be at that level.

    If I don't keep practicing it, then when I review, I feel so slow going back to pencil and paper and writing all the **** charts down before answering a question.

    But to answer your question - what is fast? For me, it would be coming up with the answer before I get the URGE to reach for pen and paper.

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    hoboscratchhoboscratch Member Posts: 11 ■□□□□□□□□□
    thanks for the input. i've been hitting subnettingquestions and i'm getting them all correct at least, which is nice. just gotta get some more practice in obviously
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    NightShade1NightShade1 Member Posts: 433 ■■■□□□□□□□
    What is true is that you need to do it because you cant waste time in silly questions like subnetting ones... you should subnet really fast in your mind.... so you can waste time in the question you really need to think....
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    lauplaup Member Posts: 9 ■□□□□□□□□□
    Yes and u have to watch your time wisely, i got punished with 3 scenarios in first 7 questions and was left with like 30 odd minutes and 43 questions left i was kackin myself.
    Still passed with 898 though :>
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    emsrescueemsrescue Member Posts: 97 ■■□□□□□□□□
    I had the same with my INTRO exam.

    The first question was the biggest senario on the exam and my brain just froze. Took me 15 mins to do a question that should have taken 2. Fortunatley the rest were not to bad so finished with 10 minutes to spare.

    I am practicing my subnetting like mad in prep for the ICND.

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    NightShade1NightShade1 Member Posts: 433 ■■■□□□□□□□
    Well for my experience in the exam the fast subnetting in my mind did it....

    I did expend like 5 mins thinking on some questions.... i remenber one took me like 10 mins
    the subnetting questions took me like 20 secs AT the end i had like 20 min left

    The bad experience on that exam was to click next on the lab thinking i could go back when i coudlnt.... lol

    Anyways i did pass with a really high score at the end so i was happy.

    The other think i must add was that i had more time because im not a native english speaker.... and i took the exam in english... taking it in english didnt bother me and i had extra time :P Actually was better becasue sometimes the trasnlation blows.... you sometimes are asking yourself WHATS that in spanish(because you just have read it in english)
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