Original MAC ID Resolution

Sharad Garg · 12-07-2010, 01:01 AM

Hi,

I am new to Linux so my question might be stupid so apologies in advance.

Qus is - I understand that user can change the MAC ID of an ethernet interface but it is on higher level.

But is there any way to get the original MAC ID (through some low level) of a PC whose Mac is changed.

Regards
Sharad

paulsm4 · 12-07-2010, 06:37 PM

"ethtool" should be able to give you the "Physical hardware address" of your Ethernet card.

Sharad Garg · 12-07-2010, 11:48 PM

Quote:

Originally Posted by paulsm4

"ethtool" should be able to give you the "Physical hardware address" of your Ethernet card.

Thanks a lot...it will definately help me.. but I think ethtool is also capable to change the MAC ID at the same level from where it reads.

So it is so, it wont help me...I want to resolve the Original MAC which was written by manufacturer of eth.

Thanks & Regards
Sharad

prodev05 · 12-08-2010, 12:29 AM

ethtool is a network packet sniffer. Also it is used to view the configuration details.

The below command will change the MAC address.

"ifconfig hw"

For more information pl refer man page.

reg

paulsm4 · 12-08-2010, 01:13 AM

Sharad Garg -

Ignore prodev05. "/usr/sbin/ethtool" is a standard Linux command; I believe it should give you the original, "Physical MAC address" that's burned in ROM.

Yes, "ifconfig hw" lets you CHANGE the "hardware address" (which, I'm guessing, you probably already knew). And yes, "ethtool" also lets you change this address.

But "ethtool" can also show you the NIC's ROM. Where, I believe, you should be able to get the address:

Quote:

ethtool -d|--register-dump ethX [raw on|off]

ethtool -e|--eeprom-dump ethX [raw on|off] [offset N] [length N]

If I'm wrong, there's also an ethtool ioctl() that should be able to help:
http://linux.derkeiler.com/Mailing-L.../msg00353.html

jefro · 12-08-2010, 04:27 PM

You have to "burn" a new mac address. (address) To change it permanently.

If it has been changed there is no way to find out unless the card had it printed on the card somewhere.

One may be able to guess the first parts but the end number would be a total guess. If you bought a set of them, they may follow sequence. In fact many cards have exactly the same number. Mac address from major companies have run out long ago.

prodev05 · 12-09-2010, 02:38 AM

Take a faulty card and replace its MAC address to the one which you want to change.

reg