with the subnet mask of 255.255.255.252, 172.16.4.0 - 172.16.4.3 would be
the 0 subnet and 172.16.4.252 - 172.16.4.255 would be the 1's subnet
? With classless routing expressing as 172.16.4.0 /30 allows the usage of
both the first and last subnets ? Is it still important to worry about
classfull routing ?
Thanks....Gary
At 01:06 PM 1/25/01 -0800, Frank Wells wrote:
>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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