Subnetting Question

Discussion in 'MCSE' started by myrt webb, Oct 10, 2003.

  1. myrt webb

    myrt webb Guest

    In a practice problem the question is how to apply IP
    addresses to 3 subnets. In part of the answer it says "The
    address 192.168.9.128/25 could be used for Subnet A, and
    the address 192.168.9.0/26 could be used for Subnet B.
    However using those addresses would require that an
    address of 192.168.9.64/27 or 192.168.96/27 be used for
    Subnet C."

    Subnet A has to accomodate 100 hosts, Subnet B 50 hosts
    and Subnet C 25 hosts.

    I need some help to understand, in the above example, how
    the addresses for A and B dictate the addresses for C.
     
    myrt webb, Oct 10, 2003
    #1
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  2. myrt webb

    asdfasdfa Guest

    hmmm i saw this problem somewhere before...somewhere in
    those cert websites...i forgot the site. oh well.
    >-----Original Message-----
    >In a practice problem the question is how to apply IP
    >addresses to 3 subnets. In part of the answer it

    says "The
    >address 192.168.9.128/25 could be used for Subnet A, and
    >the address 192.168.9.0/26 could be used for Subnet B.
    >However using those addresses would require that an
    >address of 192.168.9.64/27 or 192.168.96/27 be used for
    >Subnet C."
    >
    >Subnet A has to accomodate 100 hosts, Subnet B 50 hosts
    >and Subnet C 25 hosts.
    >
    >I need some help to understand, in the above example,

    how
    >the addresses for A and B dictate the addresses for C.
    >
    >
    >.
    >
     
    asdfasdfa, Oct 10, 2003
    #2
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  3. myrt webb

    Herb Martin Guest

    > In a practice problem the question is how to apply IP
    > addresses to 3 subnets. In part of the answer it says "The
    > address 192.168.9.128/25 could be used for Subnet A, and
    > the address 192.168.9.0/26 could be used for Subnet B.
    > However using those addresses would require that an
    > address of 192.168.9.64/27 or 192.168.96/27 be used for
    > Subnet C."
    >
    > Subnet A has to accomodate 100 hosts, Subnet B 50 hosts
    > and Subnet C 25 hosts.
    >
    > I need some help to understand, in the above example, how
    > the addresses for A and B dictate the addresses for C.


    They don't necessarily. You have to extrapolate a bit. (And
    you have to notice that the question -- as posed -- has the bits
    working the 4th octet while the differences are shown in the
    3rd octet. It's full of typos.

    25 bits leaves 7 bits, 2^7 = 128 or about 126 hosts max.
    26 bits leaves 6 bits, 2^6 = 64 or about 62 hosts max
    27 bits leaves 5 bits, 2^5 = 32 or about 30 hosts max

    Each subnet MUST begin on a "multiple" of that "power of two"
    it uses, i.e., 128, 64, 32.



    --
    Herb Martin
     
    Herb Martin, Oct 10, 2003
    #3
  4. myrt webb wrote:

    > In a practice problem the question is how to apply IP
    > addresses to 3 subnets. In part of the answer it says "The
    > address 192.168.9.128/25 could be used for Subnet A, and
    > the address 192.168.9.0/26 could be used for Subnet B.
    > However using those addresses would require that an
    > address of 192.168.9.64/27 or 192.168.96/27 be used for
    > Subnet C."
    >
    > Subnet A has to accomodate 100 hosts, Subnet B 50 hosts
    > and Subnet C 25 hosts.
    >
    > I need some help to understand, in the above example, how
    > the addresses for A and B dictate the addresses for C.


    play around with the subnet masks.





    --
    Darko Gavrilovic, MCP
     
    Darko Gavrilovic, Oct 12, 2003
    #4
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