Re: Single domain two IP subnets

"Kurt" <lorentzenkurt@xxxxxxxxxxxxxxxxxx> wrote in message
news:12gk9n8d695gc26@xxxxxxxxxxxxxxxxxxxxx
No, subnets in IP are far more than purely logical.

They practically always represent a distinct "Broadcast
domain" (area in which a broadcast will freely propagate).

Not if they're on the same wire.

That is precisely WHERE broadcasts propagate freely without
any assistance: On the same wire.

Although IP broadcasts will be discarded at the layer-3 level, Ethernet
broadcasts propogate to every node in the broadcast domain (not to be
confused with collision domain), regardless of IP subnet.

You keep introducing irrelevant issues that have little or
(absolutely) nothing to do with understanding the issues
under discussion, especially bridges, switches, routers,
VLANs, and IP Subnets.

If two machines are on the same broadcast domain they
are (practically*) always on the same subnet, and conversely
if they are not on the same broadcast domain then they are
not in the same broadcast domain.


Once again, does not apply if they are on the same wire.

Which "they"? Multi-nets are discussed below if that
is your quibble (although still largely irrelevant) but otherwise
the above has no meaning here.

[* It is theorectically possible to have multiple subnets on
the same 'wire' or 'broacast domain' but this is not a common
practice in modern networks -- and still requires some special
configuration.]

requires no special configuration at all. Get a switch, plug 4 computers
into it. Put 2 on one IP subnet and two on another. Computers on the same
IP subnet can talk, computers on disparate IP subnets cannot (at layer-3).
But if you sniff the wire at any computer, you'll see arp broadcasts and
such from every computer.

I was trying to help you but you apparently have a very poor
true understanding of switches yet do not wish to learn.

See next paragraphs...

The real problem is many the incomplete understand of of
VLANs switches, and switches in general, by many people.

One cannot understand VLANs (or any switches) completely
without first understanding the differences and features of
both Routers and Bridges -- we can call the features something
else but switches are merely "switching" combined with either
the Bridge or Router concept, or in modern devices a hybrid
of all three concepts.

True, but I must say that I don't fall into that category. As the senior
engineer/primary designer of a metro ring infrastructure, I live and
breathe VLANs and routers every day of my life. They are what make shared
ethernet infrastructures work.

You really would benefit -- if only in explaining it to others -- if
you understood the basics better then.

I will help you if you wish to learn....

VLANs switches allow the admin to (easily) redefine each
bridged segment to include arbitrary connections to the switch,
and thus map a "set of computers" to either one bridged
broadcast domain OR another to which routing is required.

The KEY to a VLAN switch is the "area" or the "component
network cables" which are BRIDGED vs. ROUTED can be
configured by the Admin using switch-commands.


--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]


.

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