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View Full Version : Changing a MAC address?



cybermatic
11-29-2001, 11:56 AM
how do you change a MAC address of a NIC in windows?

Kheldar
11-29-2001, 12:16 PM
as far as I'm aware - u can't - its the whole point of MAC addresses - they are unique to each nic/network aware device

cybermatic
11-29-2001, 12:37 PM
yeah...
i thought the same thing but i have heard that it possible to change them only i am not quite sure how!

FA-MAS
11-29-2001, 12:53 PM
The MAC addresses are hardcoded into the firmware of the NIC. I have heard of them being able to be changed by the manufacturer using a firmware update. Why would you need to change the MAC address of a NIC?

cybermatic
11-29-2001, 12:58 PM
mmm...fair enough!

i have no real reason for wanting to change it i was just curious as to whether or not it could actually be done :D

DigitalDD
11-29-2001, 11:29 PM
well normally you change the MAC address only when there is a conflict on your existing LAN but I did it on my linux router for free cable modem access for a while. it no longer works because the bootleg cable modem i bought which passes the MAC address from whatever NIC it connects to instead of using the one on the cable modem. SO since my internal NIC was a Linux firewall I just changed the MAC address on the card to something that would authenticate with the cable company. it took like 75 attempts before i found one that worked..

I have a white paper in PDF format from L0pht way back in the day here which might help..

too big to attach to this message but if you want email me and I'll pass it on..

sKuLLsHoT
11-30-2001, 05:28 AM
go to regedit.com they tell u how... a few regedits andya done

FA-MAS
11-30-2001, 08:58 AM
The MAC address is actually part of the NIC tho. Anything in the registry would be just for the OS. The only way to change the MAC address is to get a new NIC.

I do cable internet support and I get people who have gotten new NICs and can't get online. So I have to update their profile. Because the service is bound to their NIC.

cybermatic
11-30-2001, 10:16 AM
skullshot, i have just visited regedit.com...that is a cool web site! :D

DigitalDD
11-30-2001, 08:20 PM
On SUN boxes you can change the MAC with ifconfig or via the PROM-Monitor. YOu can also change the MAC address on a NIC in many of the other Unix flavors. I used to have a DOS program which would run via the config.sys file and basically LIE about what the MAC address on the NIC was.

You can also do some real hardware modding and literally reprogram the serial EPROM chip.

At last i finally found the URL of the whitepaper on MAC cloning.

http://www.atstake.com/research/reports/mac_address_cloning.pdf

its interesting reading trust me..

The Wizard
12-03-2001, 09:54 AM
it isn't possible to change the MAC address physically on a NIC unless you flash it like was mentioned before, the only other thing you could do is force the software to make it something else.. lans run on mac addresses, not ip adresses, unless you introduce routing and some other elements. but when you are say at a game lan somewhere, your computers all talk via mac addresses, not ip's. your nic only listens to traffic sent to it, not other machines, if you were to change your mac address via software (like in the os) i dont know whether you would recieve your traffic, i imagine the software will read it and take it for your nic, but im not sure on that one. cheers!!:beer: :beer:

FA-MAS
12-03-2001, 10:54 AM
it isn't possible to change the MAC address physically on a NIC unless you flash it like was mentioned before, the only other thing you could do is force the software to make it something else.. lans run on mac addresses, not ip adresses.

That is what I said earlier, so I agree fully. Without a MAC address, TCP/IP DHCP wouldn't work well. Beause when the computer boots, it's gonna broadcast for an IP because it doesn't have one. Then the first DHCP server that hears the request gives the offering. But how does the machine get the offering from the DHCP server? It doesn't have an IP address. But it's MAC address was in the packets that it boradcast for a DHCP server.

Obviosly there is more to this, but I don't wanna explain it. If you wanna find out, search for the OSI 7 layer model. And there are other examples of these types of dependency. Anyway

Later

sKuLLsHoT
12-04-2001, 08:35 PM
All the info i've seen is for software MAC changes, which is possible, in doing that one would nearly have to renew their IP manually as to the DHCP/Network machines, it would be as if u had just changed your NIC and booted again. then again...

flashin ya ROM would be another way, but thats painful, for the few advantages one or two people may gain...

in terms of the NIC having trouble with obtaining an IP, during boot up, the NIC usually has to wait until the software starts the device so by then, the software can "cloak" the MAC...

as far as my knowledge goes, this is where it stops!

SileNceR
12-04-2001, 09:05 PM
changing the EPROM would be good if u were unlucky enough to get two generic NICs with shared MAC addresses like some created by ****ty manufacturers, they use a smaller number of MAC addresses than cards they make so some re-use the MAC's... not a prob until u get a matching pair...

would be okto use software maskiung but an EPROM burn would be better if u were gonna use multi-os' etc on either machine..
alternatively one could just buy a new nic... i mean sif htey r gonna get the same nic anyway.. .except it is probable that it may happen in a workplace with say 600+ machines that in a big batch order of machines with generic nics that there MAY be double ups....

sKuLLsHoT
12-05-2001, 02:13 PM
most organisations that would buy an excess amount of PCs will spend the extra few bux for an intel or even 3com NIC, khkeldar will tell ya...

if u r buying a large volume of PCs the manufacturer should know better than to supply generic crap...

generic...hehe

DigitalDD
12-05-2001, 11:28 PM
most organisations that would buy an excess amount of PCs will spend the extra few bux for an intel or even 3com NIC, khkeldar will tell ya...

if u r buying a large volume of PCs the manufacturer should know better than to supply generic crap...

generic...hehe

I guess I'm one unlucky mofo then.. Where i work we bought 5 gross [thats 720] 3com 905C-TX NICs when we upgraded all our PCs from 10 MB NICs to 10/100 NICs.. we had 4 which had duplicate MAC addresses of others within the company.. I guess thats not bad and 3com was good enough to send us replacements free of charge. But I'm just saying that it happened with a brand name NIC to me..

SileNceR
12-06-2001, 10:23 AM
see, it happens :D

The Wizard
12-09-2001, 08:50 AM
yer the man silencer. hehe :):beer: