muslim@o2.pl wrote:

>>I wonder if it is possible at all, but I am not a programmer.
>>    
>>
>
>1. I 6 months a go see a PATH for it.
>2. Even Linux support changing of MAC adress form ifconfig.
>
>  
>
>>But while faking a
>>MAC address may be useful for debugging, I think this i far too 
>>    
>>
>dangerous.
>
>Btw. My goal to change my MAC adress is very simple:
>My ISP give my internet connection only for my XYZ Network card.
>I DONT wont to play with NAT, Masqurade etc...
>
>And I have some 386 with no PCI slot so i cant use my "internet" 
>ethernet card :( And changing the MAC adress in my old ISA ethernet 
>card is propably only legal solution...
>
>  
>
With lots of ethernet cards the MAC address is stored in one of the 
chips registers,
and *can* quite easily be (temporarily) reprogrammed. I'm not sure if 
there is any
OS support for this, but I guess there is... (haven't found it though) 
you may want
to look at ettercap or something similar to see how this program handles 
this.

Many ethernet cards store the initial MAC address in a (ee(p))rom. Some of
these (eeproms) may be reprogrammed /* in system */.
On realtek (clone) cards for instance, look for a small (8 pin) chip 
"93C46".
With a small program this chip can be reprogrammed, after which you power
cycle your computer, and your ethernet card has a new "hardware" MAC
address.

If you reprogram your MAC addres, please take care /never/ to use two 
devices
with the same MAC address on the same network segment; if you do, and you
are not lucky, you may spend ages locating the problem (irrespective if 
hubbed
or switched - you will get "funny" results if you do; however, if there 
is a router
in between, there should be no problem)

As to security: imho anyone relying on MAC addresses for security should
have his/her head examined. Faking them is just too easy.

cheers,

Theo