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!

    MD
    M D, Sep 24, 2006
    #1
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  2. M D

    LRM Guest

    "M D" <> wrote in message
    news:O1IE%...
    > 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!
    >
    > MD
    >
    >

    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
    MCNGP 7^2
    www.mcngp.com home of the bogosity singularity.
    LRM, Sep 25, 2006
    #2
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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... ;)

    Bye

    MD
    M D, Sep 25, 2006
    #3
  4. M D

    Neil Guest

    did you hear "M D" <> say in news:uDy#1AH4GHA.508
    @TK2MSFTNGP06.phx.gbl:

    > 2^y-2


    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)

    --
    The InterNeil MCNGP Triple X

    - In case of emergency, break glass. Scream. Bleed to death.
    Neil, Sep 25, 2006
    #4
  5. M D

    CBIC Guest

    "Neil" <guess!!!@gmail.com> wrote in message
    news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
    > did you hear "M D" <> say in news:uDy#1AH4GHA.508
    > @TK2MSFTNGP06.phx.gbl:
    >
    >> 2^y-2

    >
    > 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)
    >


    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
    #5
  6. "CBIC" <> wrote in message
    news:...
    >
    > "Neil" <guess!!!@gmail.com> wrote in message
    > news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
    > > did you hear "M D" <> say in news:uDy#1AH4GHA.508
    > > @TK2MSFTNGP06.phx.gbl:
    > >
    > >> 2^y-2

    > >
    > > 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)
    > >

    >
    > This thread is a little too on topic, or is it off topic. Please begin
    > discussing gun control or politics immediately.


    SHUT UP AND GO SUBNET PEOPLE.
    ~~~ The Silencer Of The Watermelons [4-8-15-16-23-, Sep 25, 2006
    #6
  7. M D

    LRM Guest

    "Neil" <guess!!!@gmail.com> wrote in message
    news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
    > did you hear "M D" <> say in news:uDy#1AH4GHA.508
    > @TK2MSFTNGP06.phx.gbl:
    >
    >> 2^y-2

    >
    > 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)
    >

    I love it when you talk technical.
    LRM, Sep 25, 2006
    #7
  8. M D

    Neil Guest

    did you hear "CBIC" <> say in
    news::

    > Please begin
    > discussing gun control or politics immediately.
    >


    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.

    --
    The InterNeil MCNGP Triple X

    - She's dead, Jim, but still warm. Let's flip a coin.
    Neil, Sep 25, 2006
    #8
  9. M D

    Neil Guest

    did you hear "LRM" <> say in news:uYosb4M4GHA.1292
    @TK2MSFTNGP03.phx.gbl:

    > I love it when you talk technical.


    I'll tell you all about SQL merge replication with horizontal partitioning
    if you take off all of yer laundry and spank me...

    --
    The InterNeil MCNGP Triple X

    - Confucius say: Early worm have death wish
    Neil, Sep 25, 2006
    #9
  10. M D

    LRM Guest

    "Neil" <guess!!!@gmail.com> wrote in message
    news:Xns9849A0F3AE468neilmcsegmailcom@207.46.248.16...
    > did you hear "LRM" <> say in news:uYosb4M4GHA.1292
    > @TK2MSFTNGP03.phx.gbl:
    >
    >> I love it when you talk technical.

    >
    > I'll tell you all about SQL merge replication with horizontal partitioning
    > if you take off all of yer laundry and spank me...
    >

    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
    #10
  11. M D

    Neil Guest

    did you hear "LRM" <> say in
    news::

    > 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.


    INDIVIDUALLY sharpened? I feel so special...

    (I might have to go over vertical partitioning too)

    --
    The InterNeil MCNGP Triple X

    - Members of avian species of identical plumage congregate!
    Neil, Sep 25, 2006
    #11
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