Could you please pass the url for the web-page?
Thanks in advance.
Brian Lodwick wrote:
>
> Group,
> I feel like I have come to a nice understanding on this issue. Many thanks
> to Howard Berkowitz, Radia Perlman's book, and I must apologize there was
> another groupstudy member who referrenced a webpage that was really
> helpfull, but I can't remember his name.
> If anyone is interested this is what I have come to understand.
> This as Howard had mentioned is only applicable in a classfull environment.
> There are infact good reasons why the all 0's subnet was not used and why
> the all 1's subnet was not used. These weren't hard and fast rules, but were
> emphatically reccomended in a classfull environment. The reason being that
> when routing information is distributed in a classfull environment the
> prefixes aren't sent and defualt barriers are set for the masks. In the
> instance where an all 0's subnet was used there would be no way to decipher
> between say
> 192.168.15.0/24 and 192.168.15.0/28 sent in a routing update.
> The all 1's subnet is a similar issue accept in this instance it would not
> be possible to send a routing update to indicate subnet multicasts.
> This is quite an interesting concept and I appreciate everyones help
> understanding this issue.
>
> >>>Brian
>
> >From: "Donald B Johnson Jr" <[EMAIL PROTECTED]>
> >Reply-To: "Donald B Johnson Jr" <[EMAIL PROTECTED]>
> >To: "Brian Lodwick" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]>
> >Subject: Re: ip subnetting
> >Date: Wed, 27 Dec 2000 10:02:42 -0800
> >
> >you can break it down with vlsm and reclaim most of the space.Duck
> >----- Original Message -----
> >From: Brian Lodwick <[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>
> >Sent: Wednesday, December 20, 2000 4:25 AM
> >Subject: ip subnetting
> >
> >
> > > Group,
> > > In determining valid subnetworks it used to be true all were valid
> >accept
> > > the all 1's subnet and the all 0's subnet. In an environment where all
> > > devices are compatible, I understand, that by using the configuration
> > > command "ip subnet-zero" it enables the use of the all 0's subnet. The
> > > question I ask then, wouldn't that leave the all 1's subnet still an
> >invalid
> > > subnet even when using the previous mentioned command? or is there
> >something
> > > else that allows the all 1's subnetwork? I have been asked this
> >question,
> > > and I don't feel I am correct. The new formula noted in the CCNA book
> >notes
> > > the new equation for determining the amount of valid subnetworks is 2^#
> >of
> > > subnet bits, and I figured it would be 2^#of subnet bits - 1 (for the
> >all
> > > 1's subnet). I don't pose this question without first a bit of research
> >and
> > > everything I have read indicates the "ip subnet-zero" command only
> >enables
> > > the use of the all 0's subnetwork. I however cannot find anything
> >indicating
> > > the use of the all 1's subnet is permitted. Any help is appreciated.
> > >
> > > >>>Brian
> > > _________________________________________________________________
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--
----------------
Shabbir S. Talib
MCSE, CNE, CCNA
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