From: Wes Stevens (wrsteve33-gsccie@yahoo.com)
Date: Wed Sep 14 2005 - 18:39:37 GMT-3
The only way two devices can talk that are not using
the same mask is if both have the same broadcast
address and both fit into the range of the smaller of
the two masks. For example a router with an address of
192.168.1.254 with a /24 mask and a device with the
address of 192.168.1.129 with a /25 mask will be able
to talk to each other. When we put in ranges we often
reserve a /23 range in our ip address plan and then
use only the upper /24 of that range. In the future if
that range needs to expand then it makes for an easy
expansion. If not the other part of the range can be
used seperately.
--- Anthony Sequeira <terry.francona@gmail.com> wrote:
> I was under the false assumption that subnet masks
> must be identical in
> length for two systems to communicate. But I do not
> believe this to be true.
> Isn't it a fact that the addressing just has to work
> out so that the two
> systems think they are on the same subnet?
> Can someone help me with the binary math that you
> would do to figure this
> out?
> For example, let's say my router interface is
> 172.16.1.1/25<http://172.16.1.1/25>and I want to use
> /24 for all of my
> clients off of that interface. What is
> the quickest way to calculate the usable range of
> addresses for these
> client?
>
>
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