Cloned MAC address?

Nils Kassube kassube at
Fri Aug 12 05:26:02 UTC 2011

Bill Stanley wrote:
> I was exploring the GNOME desktop and found something interesting. 
> When right clicking the Network management Applet icon there is an
> item that says "Edit Connections".  I clicked on this and then on
> one of the items, "Auto Eth0", which the applet says is never used. 
> There is nothing interesting yet but one of the options is "cloned
> MAC address". Is a different MAC address reported to the Internet
> instead of the actual MAC address?  I don't intend to do anything or
> do any editing of the settings, I am just curious.

Usually a hardware interface has a preset MAC address. However for most 
(all?) interfaces you can overwrite the MAC address by software. This is 
particularly useful if your ISP has a setup where you can only connect 
with a specific MAC address. Then, if you replace the hardware that 
connects to your ISP, you could set the new hardware to that previously 
used MAC address to connect again without calling them to request a 
change in their setup for your new hardware.

OTOH, this feature is also the reason why MAC address filters for your 
WLAN router are useless - everybody can fake the address of a station 
that is allowed by the filter.


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