[c-nsp] Current CCNA tests

[Gert Doering]

Hi,

On Tue, Jan 08, 2008 at 11:17:51PM +0000, A.L.M.Buxey at lboro.ac.uk wrote:
> > I may be pedantic now (it' getting late!), but "ip subnet-zero" doesn't
> > change the number of hosts you can cram into an unsubnetted /24
> > network, class C or otherwise, does it? As I understand it, it just
> 
> pretty much right - it allows you to use some freaky /24's within your
> available space - but its more important when using /23's and the
> like where you can use .0 and .255 addresses within the space.

Actually, "ip subnet-zero" has nothing whatsoever to do with the addresses
available for hosts in a /23.

The difference is whether the router will permit you to configure things
like

   ip address 193.31.7.1 255.255.255.240

or insist that you must skip the first ("zero") subnet in a non-VLSM
subnetted Class X network.

Whether or not you can use a /23 from Class C space (and subsequently, 
.255 and .0 in the middle of it for hosts addressing) purely depends on
the age of your IOS.  IOS up to 10.2 did not permit supernets, IOS 10.3 did.

In the century of CIDR, all this is completely meanlingless anecdotal
material from the last century.

gert

-- 
USENET is *not* the non-clickable part of WWW!
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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