I have 2 wireless cards with the same MAC address at the hotel

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?

Jette

On Sat, 30 Sep 2006 13:35:49 GMT, Jette Goldie wrote:

><snip>
>
> 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?
>
> Jette

Because the packets are not routed to a mac address they are route to an IP
Address.

"Jette Goldie" <(E-Mail Removed)> wrote in message news:1vn85ksiuz92m.16q1rgqxl8v3e$.(E-Mail Removed).. .
>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?
>
> Jette


Are they connected to same access point?

--PA

"Jette Goldie" <(E-Mail Removed)> wrote in message
news:1vn85ksiuz92m.16q1rgqxl8v3e$.(E-Mail Removed).. .
>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

Jette Goldie wrote:

> I have two working PCs with the same MAC address!
> How do the packets figure out which computer to go to?

If you assigned the MAC on one, and left the other in it's original form,
the MAC's are actually one bit apart: The last bit indicates that the MAC
was set and not the factory MAC address.

--
Baloo
email & xmpp: (E-Mail Removed)

FedUp wrote:

>
> On Sat, 30 Sep 2006 13:35:49 GMT, Jette Goldie wrote:
>
>><snip>
>>
>> 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?
>>
>> Jette
>
> Because the packets are not routed to a mac address they are route to an
> IP Address.

At the network level, maybe, but not at the data link level. You might want
to read up on the OSI 7 Layer Model before making such statements.

--
Baloo
email & xmpp: (E-Mail Removed)

Does not compute! MAC is a hardware address "permanently burned-in" by the
manufacturer. If Windows detects two identical MACS a system event log
entry is generated and network connectivity cease.

Following also quoted from Knowledge Database Article ID 164903: "Another
source of duplicate media access control addresses can occur if you are
assigning locally administered media access control addresses (LAA), in
which case you are overriding the burned-in address in favor of the locally
assigned media access control address. With some drivers, LAA media access
control addresses are possible, usually Token Ring adapter drivers."


"Jette Goldie" <(E-Mail Removed)> wrote in message
news:1vn85ksiuz92m.16q1rgqxl8v3e$.(E-Mail Removed).. .
>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?
>
> Jette

"Jette Goldie" <(E-Mail Removed)> wrote in message
news:1vn85ksiuz92m.16q1rgqxl8v3e$.(E-Mail Removed).. .
>I have two working PCs with the same MAC address!
> How do the packets figure out which computer to go to?

>
> 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?
>
> Jette

> Both computers seem to be working wirelessly [perfectly].

Keyword: "seem"

Run Ethereal or some SNMP utility and you'll probably find quite a bit of
collisions going on...

Please quote in the same manner we all read English: Conversational order.
Please see http://ursine.ca/Top_Posting

AJR wrote:

> Does not compute! MAC is a hardware address "permanently burned-in" by the
> manufacturer. If Windows detects two identical MACS a system event log
> entry is generated and network connectivity cease.

Not necessarily. Some devices, such as some high end network cards and SOHO
routers, have the ability to set the MAC address. One of the MAC address
bits, IIRC, indicates whether the MAC was set by human intervention or the
one it shipped with.

--
Baloo
email & xmpp: (E-Mail Removed)

"AJR" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Does not compute! MAC is a hardware address "permanently burned-in" by the
> manufacturer.

Drive-by replying?

Read his post again...

("so I used MacMakeUp to make both computers have the same MAC address")

That computes how he could have two NIC's with the same MAC.