70-291: Wrong VLSM study question?

Discussion in 'MCSE' started by Corrado Labinaz, Dec 2, 2004.

  1. Hi to everyone,
    following a question from a 70-291 study exam, with the suggested correct
    responses.
    I belive these responses are wrong.
    First take a look at the question:

    ----------------------------
    Your organization has leased the Class C network 199.205.15.0/24. You are
    subnetting this network
    using VLSM. Your routers support the zero subnet and the longest match
    algorithm. You ask one of
    your support staff to design a subnetting structure, but when she submits
    this you suspect that some
    of the network/subnet mask allocations are invalid. Which of the following
    are not valid networks?
    (Choose all that apply).

    1. 199.205.15.64/25 <Correct>
    2. 199.205.15.8/27 <Correct>
    3. 199.205.15.130/26 <Correct>
    4. 199.205.15.192/26
    5. 199.205.15.40/28
    6. 199.205.15.96/26
    ----------------------------

    AFAIK, looking at the last octet of the above addresses and masks,
    199.205.15.64/25 equate to
    01000000 address
    10000000 mask.
    This mean not all host bits are set to 0, so this is not a valid network.
    The same goes for:
    199.205.15.8/27
    199.205.15.130/26
    199.205.15.40/28
    199.205.15.96/26

    The only valid network is 99.205.15.192/26.

    What do you think?

    Kind regards,
    Corrado
     
    Corrado Labinaz, Dec 2, 2004
    #1
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  2. Corrado Labinaz

    Kurt Guest

    Valid networks in a /25
    0, 128
    Valid networks in a /26
    0, 64, 128, 192
    Valid networks in a /27
    0, 32, 64, 96, 128, 160, 192, 224
    Valid networks in a /28
    0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240

    So......

    1. 199.205.15.64/25 <Nope>
    2. 199.205.15.8/27 <Nope>
    3. 199.205.15.130/26 <Nope>
    4. 199.205.15.192/26 <Yep>
    5. 199.205.15.40/28 <Nope>
    6. 199.205.15.96/26 <Nope>

    I'd say you're right!



    "Corrado Labinaz" <> wrote in message
    news:...
    > Hi to everyone,
    > following a question from a 70-291 study exam, with the suggested correct
    > responses.
    > I belive these responses are wrong.
    > First take a look at the question:
    >
    > ----------------------------
    > Your organization has leased the Class C network 199.205.15.0/24. You are
    > subnetting this network
    > using VLSM. Your routers support the zero subnet and the longest match
    > algorithm. You ask one of
    > your support staff to design a subnetting structure, but when she submits
    > this you suspect that some
    > of the network/subnet mask allocations are invalid. Which of the following
    > are not valid networks?
    > (Choose all that apply).
    >
    > 1. 199.205.15.64/25 <Correct>
    > 2. 199.205.15.8/27 <Correct>
    > 3. 199.205.15.130/26 <Correct>
    > 4. 199.205.15.192/26
    > 5. 199.205.15.40/28
    > 6. 199.205.15.96/26
    > ----------------------------
    >
    > AFAIK, looking at the last octet of the above addresses and masks,
    > 199.205.15.64/25 equate to
    > 01000000 address
    > 10000000 mask.
    > This mean not all host bits are set to 0, so this is not a valid network.
    > The same goes for:
    > 199.205.15.8/27
    > 199.205.15.130/26
    > 199.205.15.40/28
    > 199.205.15.96/26
    >
    > The only valid network is 99.205.15.192/26.
    >
    > What do you think?
    >
    > Kind regards,
    > Corrado
    >
    >
    >
     
    Kurt, Dec 5, 2004
    #2
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