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  1. #1
    Master Untangler
    Join Date
    Apr 2007

    Default When to use /8, /24, /32 etc IP Adressing 101

    This may be a rather dumb question, but I have not used this kind of addressing until I started using untangle.

    What would be the cases to use:

    Consider this an IP addressing 101, I know this type of naming has a "name" but cannot remember it off the top of my head.

    Thanks for putting up with a big dummy...

  2. #2
    Master Untangler
    Join Date
    Oct 2008


    this one explains subnets pretty well.

  3. #3
    Untangle Ninja mrunkel's Avatar
    Join Date
    Jul 2008


    If you realize that these are all binary numbers, then it makes more sense:

    The /n = netmask with n number of 1's.

    255 = in binary is 11111111 = 1111111100000000000000000000 or 8 ones = /8 = 1111111111111111111100000000 or 24 ones = /24 = 1111111111111111111111111111 or 32 ones = /32

    The reason people switched from the nomenclature to the /8 is because with the advent of classless internet numbers a whole lot of new subnet masks starting showing up. How many bits in the address field in at or It's much easier to look at /23 ( and know that you have 9 bits in the address field since an IP address is 32 bits long.
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  4. #4
    Untangle Ninja Solignis's Avatar
    Join Date
    Jul 2008
    Hudson, Ohio, USA


    wow just this thread brings back CCNA Level 1.

    Ah the horrors.

    Also if you are lazy like me, download solarwinds ip subnet calculator.

    In my cisco class my teacher made us subnet on paper, it sucked.
    “Most good programmers do programming not because they expect to get paid or get adulation by the public, but because it is fun to program.” - Linus Torvalds

  5. #5
    Master Untangler mozerd's Avatar
    Join Date
    Nov 2008
    Nepean Ontario Canada

    Default Cidr

    Quote Originally Posted by bigdessert View Post
    Consider this an IP addressing 101, I know this type of naming has a "name" but cannot remember it off the top of my head.
    CIDR - Classless Inter Domain Routing

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