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
> > _________________________________________________________________
> > Get your FREE download of MSN Explorer at http://explorer.msn.com
> >
> > _________________________________
> > FAQ, list archives, and subscription info:
>http://www.groupstudy.com/list/cisco.html
> > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>
>_________________________________
>FAQ, list archives, and subscription info:
>http://www.groupstudy.com/list/cisco.html
>Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
