Comments Inline
At 11:43 AM 1/16/01 -0600, you wrote:
>Hmm, I think I know what the question is, however I don't really have an
>answer right now if I'm right.
>
>Picture two different scenarios:
>
><<1>>
>
>Workstation A, B and C are connected to a switch that IS NOT running VLAN,
>hence they are in the same broadcast domain. The IP addresses are as
>follows:
>
> A : 10.0.0.10 / 8
> B : 10.0.0.11 / 8
> C : 192.168.29.14 / 24
>
>If A wants to send to C, it broadcasts an ARP request for 192.168.29.14
>which the switch forwards to C, and C replies back with it's MAC address,
>and A can now send to C.
>
>This is however (I believe) a bad configuration.
>
Actually this won't happen. Host A has no idea it is on a common broadcast
domain with Host C. It will just look at the address and see that it is on
a different network and because of this it will forward the packet to the
default gateway. The only way it would issue an ARP request is if it was
on the same IP network as Host A. This is default IP behavior.
><<2>>
>
>Workstation A, B and C are connected to a switch that IS running VLAN, and
>with the same IP addresses as in example 1, A and B are in VLAN 11 and C is
>in VLAN 12 - hence they are in two different broadcast domains.
>
>If A wants to send to C, it broadcasts an ARP request for 192.168.29.14, but
>the switch does not forward it since C is on a different broadcast domain.
>
>A now has to send the data to it's Default Gateway.
>
>
>I think that the question is : If you take example 2, why doesn't the switch
>just reply to station A's ARP request with C's MAC address, so A can send
>directly to C anyway.
Once again it is because Host A will never broadcast an ARP request. Hosts
only broadcast ARP requests when it is on the same network. The exception
to this would be if you did not configure Host A with a default gateway in
which case I believe it would just throw out an ARP request, but I don't
think this would be the best practice.
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