>a station doesn't send an ARP for a station not on its subnet.
>(There are workarounds to this, such as not configuring a default
>gateway
I don't believe that this is correct.
If there is no route, default or better, to the other (sub)network, then
you'll get something like
"network unreachable"
or
"host unreachable"
>or making the default gateway your own address.)
This is the trick that I was talking about -- more specifically, adding
a route to the *particular* (sub)network of the other node, rather than
the disruptive default route.
... and I've actually used it, but, I never thought too deeply about how
it works.
I (the PC with default-to-self) still have to get the packet to the
other node, whose destination IP address is on another IP subnet (even
though we're "on the same wire").
So, ISTM, I have 2 choices:
1: put the packet out as a local MAC broadcast
or
2. Do an ARP for the other IP address, even though it's not in my
logical IP (sub)network.
(I'm certainly *not* going to ARP for own address (which is now the
default gateway).
)
Either choice is non-normal (or, at least, non-familiar :) behavior, so
I'm wondering whether this is defined somewhere in an RFC?
Actually, is this trick discussed *anywhere* ?
OTOH, maybe I'm just being dense and it's not a "trick" at all, but
dunangme if I can figger out how it works :|
-----------------------------------------------
Tks | [EMAIL PROTECTED]
BV | [EMAIL PROTECTED]
Sr. Tech. Consultant, SBM
Vox 770-623-3430 11455 Lakefield Dr.
Fax 770-623-3429 Duluth, GA 30097-1511
===============================================
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Priscilla Oppenheimer
Sent: Wednesday, January 31, 2001 8:48 PM
To: [EMAIL PROTECTED]
Subject: RE: Ethernet switching
At 04:32 PM 1/31/01, Fred Danson wrote:
>Ok, now from my understanding, each port on a switch is its own collision
>domain. As far as broadcast domains go, if a switch is not setup for
>multiple VLANs, then everything on the switch is considered to be in the
>same broadcast domain, no matter what is running at layer 3.
You are right. The original reply that brought collision domains into the
picture muddied the waters.
You make an important point about broadcasting. I think people forget that
all devices on a switched network (regardless of IP subnetting or other
layer-3 issues) hear each other's broadcasts, unless VLANs are configured.
The other thing that was missing, though, (as many people have mentioned),
was that a station doesn't send an ARP for a station not on its subnet.
(There are workarounds to this, such as not configuring a default gateway
or making the default gateway your own address.)
Priscilla
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