How to change MAC address of LAN adapter ?

Posted on 2000-03-09
Last Modified: 2008-03-04
Is there any way to do that?
If yes please explain how. I use 3COM Etherlink 10/100 PCI (3C905B-TX) adapter.
Also is it a common practice to log what has been done from which MAC address?

Question by:levx
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LVL 12

Expert Comment

ID: 2599615
No, you can't change the MAC address of an Ethernet adapter. This is a hard-coded number which the manufacturer guarantees to be unique, so no two adapters will have the same MAC address: this guarantee wouldn't be worth much if you could change it!
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Expert Comment

ID: 2599921
>Also is it a common practice to log
>what has been done from which MAC

Did you do something you shouldn't have?


Expert Comment

ID: 2600123
MAC adress can't be changed BUT you can use LAA (Locally Administered Adress).It's a feature on token ring card but also on ethernet (ithink). This adress will be used instead of MAC on the network so you must check that no other network cards as this adress.
You can change LAA on 3COM card with drivers (depending on version) or with a program (downloadable from 3COM web site) named something like 3C5x9CFG.

Hope this would help
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LVL 12

Expert Comment

ID: 2600409
hdevaux: Thats a Tokenring-only feature.

as far as i know there is no way to change the MAC of anything (well, you can do it on SUN workstation, with a lot of trickery) ANd i hope you cant. Imaging the chaos that would result.
LVL 32

Expert Comment

ID: 2600521
In general, it's not possible to change the MAC address of an Ethernet card.  In most cases it's stored in programmable memory on the card.

Some systems, like the Sun, save it in system configuration memory and it can be changed.  On some network cards there is a separate PROM chip that can be removed and replaced.  On others, like the newer 3COM board you have, the MAC is stored in the controller chip and there is not a documented way of modifying it.
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Expert Comment

ID: 2600529
Just a comment.. The real reson for being able to change the MAC of suns is because the MAC is used in the "fingerprint" of the machine and some software packages (such as microstation) uses this fingerprint for licencing.
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Expert Comment

ID: 2600594

Actually Suns also have a "hostid" which is not stored in the CMOS RAM on the motherboard but is stored on a PROM chip.  If you have your Sun box serviced and it requires a motherboard swap, the service technician is supposed to move the ID PROM from the old motherboard to the new one so that any licensed software will continue to be licensed.

I know that some companies tie their licenses to the MAC address but this is a foolish practice since:

1) It's easily changed on some SUN models.

2) It's not always constant.  Some Sun's have SBus Ethernet cards and these can be changed.

3) There may be more than one network card, and hence more than one MAC in a given system.
LVL 63

Expert Comment

ID: 2601156
I seem to remember that some NIC's had a utility that allowed changing the MAC address. If you do not have it on your driver disks, check out the manufacturers site. This was popular during the NE2000 clone days especially.  I hope this helps.

Accepted Solution

cooljudson earned 200 total points
ID: 2602030
You cannot change the MAC address of a network device.  These numbers are "burnt" into the device at the factory and are not changeable.  Networks are not able to function with 2 devices using the same MAC address.  This keeps you from changing your MAC address to someone else's address and getting them in trouble by hacking into someone's network.  The MAC address is a serial number and security mechanism.  Don't know why you would want to try, but just can't be done...
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Expert Comment

ID: 2602042
cool: it can som some devices. there are perfectly legit reasons.. but that discussion isnt really relevant.

Author Comment

ID: 2602250
well,looks like it really can't be done:(

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