70-293 question: correct subnetting formula

Discussion in 'MCSE' started by M D, Sep 24, 2006.

  1. M D

    M D Guest

    Hi everybody!

    I'm preparing 70-293 on MS press Self Paced training Kit first version.
    At Chapter 2 it says that to find out how many sbunetted networks are
    available you just need to calculate 2^y-2 (where y is the n° of the
    subnetted bits).
    My question is: isn't this obsolete? From what I studied in 70-291 it's
    since mid 90's that this rule as been overcome by the 2^y!
    Any help?

    Thanks a lot!

    M D, Sep 24, 2006
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  2. M D

    LRM Guest

    Not in a subnet. In subnetworks, however, it is likely but not always the
    case. There is still the one off old device that will require that you
    remove them. In a subnet you will still need to remove the network and
    broadcast bit in order to determine the number of usable addresses.
    LRM, Sep 25, 2006
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  3. M D

    M D Guest

    Hi LRM!

    Thanks LRM for your reply.

    For what I understand, this means I should always use the 2^y-2 formula if
    not differently advised in a question of the exam?

    Still trying to make up my mind... ;)


    M D, Sep 25, 2006
  4. M D

    Neil Guest

    now, you see, this is where the confusion comes in. It's 2^n-2, not 2^y-2.

    (and though there are some texts that indicate that it should be jut 2^n,
    the math just doesn't work out from the theoretical point. Sure there are
    some routers that work with the all 0's and all 1's for the subnetwork, but
    it SHOULD be reserved for the subnet broadcast (all 1's) and the subnetwork
    identifier (all 0's) if you ask me)
    Neil, Sep 25, 2006
  5. M D

    CBIC Guest

    This thread is a little too on topic, or is it off topic. Please begin
    discussing gun control or politics immediately.
    CBIC, Sep 25, 2006
    ~~~ The Silencer Of The Watermelons [4-8-15-16-23-, Sep 25, 2006
  7. M D

    LRM Guest

    I love it when you talk technical.
    LRM, Sep 25, 2006
  8. M D

    Neil Guest

    Subnetting gun control seems like the more politically correct route. We
    will begin by controlling only the Hand Guns (because as we all know that
    Hand guns are a class C network) as that one can be only subdivided a
    little and Large Automatic weapons (a class A network) could have thousands
    of subnets - too much math.
    Neil, Sep 25, 2006
  9. M D

    Neil Guest

    I'll tell you all about SQL merge replication with horizontal partitioning
    if you take off all of yer laundry and spank me...
    Neil, Sep 25, 2006
  10. M D

    LRM Guest

    Ok, if you would have a seat in my comfy chair upholstered in a plush carpet
    of individually sharpened spikes. Got it special for these occasions. I'll
    slip into something a little less restrictive.
    LRM, Sep 25, 2006
  11. M D

    Neil Guest

    INDIVIDUALLY sharpened? I feel so special...

    (I might have to go over vertical partitioning too)
    Neil, Sep 25, 2006
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