[Udpcast] Big Problem with cloned MACs

Alain Knaff alain at knaff.lu
Sun Feb 17 19:46:47 CET 2008

> Actual (The Moment the problem occurs):
> Then I found about UDPCast (and G4L) giving it a try. I made a Master-PC  
> (setting up everything) and booted UDPCast from CD using it as a server, 
> which has ww:xx:yy:zz:60:0a as its original MAC on its Onboard NIC. This 
> mac is also printed on the motherboard. Cause the Motherboards are from 
> allmost one series, the MAC-Addresses are allmost identical except for 
> the last 4 positions (ww:xx:yy:zz: is equal to all NICs)
>  Then i booted several PCs from CD setting them up as UDP-Cast-clients. 
> UDPCast runs fine at this point. After _several_ minutes (=hours), the 
> imaging was done. Then I rebootet, trying to finish the Clients to hang 
> them into a M$-Domain and so on. Strange Errors occured then. I couldn't 

So, I suppose you booted into windows at that point....

> change their names, Ping to the IP did not work properly, ... I saw the 
> mac, and when I looked to the DHCP-Server Logs, it looked strange, all 
> had one and the same MAC, which is the MAC of the UDPCast server!

I suppose what happened here is some Windows bogosity, or rather some 
Nvidia-driver-on-windows bogosity:

- Probably, for some weird reason, the Nvidia driver (or one autostart 
program associated with the Nvidia driver?) changes the value of the Mac 
address in the Eprom towards an address stored somewhere in the registry 
(or somewhere else).

What to do:
1. Try talking to Nvidia tech support about it
2. Try searching the registry for the "bad" Mac address, and replace 
each occurrence with the "correct" address. ... or, if you want to trace 
the error, replace each occurrence with a different address, and then 
check later which one of these "sticks"...

> of the UDP-Cast Server. (UDPCAST-Server switched off). Until this point, 
> there was no other software runing on this machine.

Sorry, you did mention Windows. This *is* other software, which might 
very well do strange things to the Nic. If not Windows itself, then at 
least Nvidia's drivers or associated software might do it...

Try once doing an Udpcast, and *immediately* boot into Knoppix after 
that, and check the Mac address. I'm pretty sure that the Mac address 
stays the same until Windows is booted once.

> I could live with that, if there would exists a Tool, to change the wrong 
> MAC back to its original value! But nothing found yet...

Probably the same tool that changed it to wrong in the first place. Try 
having a closer look at the Nvidia drivers, and at the registry...



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