"Jette Goldie" <bosslady@scotlandmail.com> wrote in message
news:1vn85ksiuz92m.16q1rgqxl8v3e$.dlg@40tude.net.. .
>I have two working PCs with the same MAC address!
> How do the packets figure out which computer to go to?
>
> I have been travelling with two computers for weeks now staying at some
> German hotels whose wireless ISP sync with the MAC address of the wireless
> cards on my computers so I used MacMakeUp to make both computers have the
> same MAC address as I get my home email on my home PC and I get my work
> email on my work PC. Up until today, I was careful to boot only one
> computer at a time.
>
> I'm currently in a hotel in the UK which has free wireless to any MAC
> address and I forgot to reset the MAC address on the second PC back to the
> original. Both computers seem to be working wirelessly.
>
> How can that be?
>
> How can I have two working PCs with the same MAC address?
> Why don't the packets get confused as to which computer to go to?
>

It's because a NAT device such as a router is being used. The router has a
DHCP server that issues an unique IP to each NIC requesting that an DHCP IP
be issued to it. NAT is mapping technology it maps traffic back to the
requesting IP/machine's NIC that sent outbound traffic to a remote IP on the
Internet. Not only does the router apply the MAC in the network traffic when
it sends traffic outbound, it also applies the LAN IP that has been assigned
to the NIC too in the traffic, so that the inbound traffic can be mapped
back to the requesting machine. Inbound traffic is not mapped back to a
machine, unless there is corresponding traffic sent outbound by the machine,
which has a LAN IP.

Duane :)