Hey Jen,
Your understanding of subnetting is a little off and your teaching is thus
tainted. Here is a how subnetting and subnet zero work:
Take a IP address for example: 172. 16. 4. 0
Add an easy subnet mask to play with: 255.255.255.252
What subnets to we get from this combo?...
First subnet= 172.16.4.4
Second subnet= 172.16.4.8
Third subnet= 172.16.4.12
...
Last subnet= 172.16.4.252
Lets examine one of the subnets: 172.16.4.4
The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7
The first and last IP addresses in the subnet range are the network address
and subnet broadcast address respectively, and neither the first or last
address can be used for host addressing, as is
well known. This leaves two remaining addresses available for hosts on that
subnet:
172.16.4.5 and 172.16.4.6
Subnet zero is that address space which is not taken up by the subnets. In
our example this would be 172.16.4.1;172.16.4.2;172.16.4.3
Routers do not use subnet zero for anything unless instructed to do so and
if this is the case, they will merely recognize it and route it. The
broadcast address in a subnet does not see the entire network, it broadcasts
only to its entire sub-network. Referring to our example once more, this
would be the address 172.16.4.7 and only the two host addresses on the
subnet would hear a broadcast from it.
Hope this clarifies things.
>From: Jennifer Cribbs <[EMAIL PROTECTED]>
>Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Subject: RE: Ip addressing question
>Date: Thu, 25 Jan 2001 10:38:38 -0500
>
>Subnet zero is the network address that the routers uses for routing to the
>network and the broadcast address sends a broadcast to the entire network
>everytime it is used, which means it goes to all subnets. Therefore, these
>are not used as host addresses. They encompass the whole network. Others
>can
>probably add to this.
>
>Jennifer Cribbs
>
>
>===== Original Message From "Fred Danson" <[EMAIL PROTECTED]> =====
> > Could anyone explain to me why Subnet zero and the last subnet are
>not
> >normally used?? I see why 2 host addresses are reserved in every subnet
> >(network address and broadcast address), but I never understood why 2
> >networks are not used. What is the difference between these networks and
>the
> >networks in between?
> >
> >Thanks in advance,
> >
> >Freddy
> >
> >
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>------------------------------------------------------------
>Have a Good Day!!
>Jennifer Cribbs
>[EMAIL PROTECTED]
>
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