[gPXE] how to change MAC address

[Marco Giunta]

Unfortunately, same result:

Ethernet frame source address: original mac address

DHCP request 'Client MAC address': modify mac address

even if I unplug and plug again network cable ....

    Marco


Joshua Oreman wrote:
> On Wed, May 5, 2010 at 4:09 AM, Marco Giunta <giunta at sissa.it> wrote:
>   
>> Hi at all,
>> I'm a sysadmin in an Italian college; for security reason, our PXE
>> server allows only few and well known MAC addresses. When I change mac
>> address with gPXE command:
>>
>> gPXE> set net0/mac ff:ff:ff:11:22:33
>>
>> and then I check new mac address with:
>>
>> gPXE> show net0/mac
>> net0/mac = ff:ff:ff:11:22:33
>>
>> it seems changed, but if I want to get a DHCP address, with:
>>
>> gPXE>dhcp net0
>>
>> I receive 'Connection timed out' error.
>> With Wireshark, I found that mac address is not changed, but is only
>> spoofed; in fact, every ethernet frame send by the card has as source
>> address the original network card mac address, but DHCP request has done
>> with new mac address (ff:ff:ff:11:22:33). Of course, our dhcp server,
>> replies with a DHCP offer to new mac address, so the network card cannot
>> accept the offer.
>>
>> My question is: is this behaviour right ? I mean, command 'set netX/mac'
>> should be only use for spoofing mac address in network request, or
>> should really change mac address, like unix command 'ifconfig eth0 hw
>> ether ff:ff:ff:11:22:33' ??
>>     
>
> For almost all drivers, the MAC address needs to be set before the
> card is initialized. Thus, you should do
> gPXE> ifclose net0
> gPXE> set net0/mac ff:ff:ff:11:22:33
> gPXE> ifopen net0
> gPXE> dhcp net0
>
> -- Josh
>
>   
>> Thank you,
>>    Marco
>>
>> _______________________________________________
>> gPXE mailing list
>> gPXE at etherboot.org
>> http://etherboot.org/mailman/listinfo/gpxe
>>
>>     

-- 
 -----------------------------------
|Marco Giunta - SISSA Computer Staff|
|Via Beirut, 2-4                    |
|34151 -  Trieste, Italy            |
|Tel: +39-40-3787-503               |	
|Fax: +39-040-3787-528              |
|e-mail: giunta AT sissa.it         |
 -----------------------------------