70-293 question: correct subnetting formula

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

LRM
Sun Sep 24 22:41:21 CDT 2006

"M D" <mdbl@NOSPAMinwind.it> wrote in message
news:O1IE%23XC4GHA.2420@TK2MSFTNGP02.phx.gbl...
> 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.

M
Mon Sep 25 01:59:59 CDT 2006

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

Neil
Mon Sep 25 10:42:50 CDT 2006

did you hear "M D" <mdbl@NOSPAMinwind.it> 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.

CBIC
Mon Sep 25 10:47:36 CDT 2006


"Neil" <guess!!!@gmail.com> wrote in message
news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
> did you hear "M D" <mdbl@NOSPAMinwind.it> 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.

~~~
Mon Sep 25 11:15:00 CDT 2006


"CBIC" <spam.thisbiotch@gmail.com> wrote in message
news:eTkuYoL4GHA.1256@TK2MSFTNGP04.phx.gbl...
>
> "Neil" <guess!!!@gmail.com> wrote in message
> news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
> > did you hear "M D" <mdbl@NOSPAMinwind.it> 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.

LRM
Mon Sep 25 13:12:02 CDT 2006

"Neil" <guess!!!@gmail.com> wrote in message
news:Xns9849772941E21neilmcsegmailcom@207.46.248.16...
> did you hear "M D" <mdbl@NOSPAMinwind.it> 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.

Neil
Mon Sep 25 14:47:39 CDT 2006

did you hear "CBIC" <spam.thisbiotch@gmail.com> say in
news:eTkuYoL4GHA.1256@TK2MSFTNGP04.phx.gbl:

> 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
Mon Sep 25 14:49:20 CDT 2006

did you hear "LRM" <Fskspam@friedspam.com> 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

LRM
Mon Sep 25 15:09:26 CDT 2006

"Neil" <guess!!!@gmail.com> wrote in message
news:Xns9849A0F3AE468neilmcsegmailcom@207.46.248.16...
> did you hear "LRM" <Fskspam@friedspam.com> 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.

Neil
Mon Sep 25 15:27:57 CDT 2006

did you hear "LRM" <Fskspam@friedspam.com> say in
news:u6DJE6N4GHA.4648@TK2MSFTNGP04.phx.gbl:

> 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!