I've been working last months on a lubbock board and u-boot as a bootloader to run Linux. I always loaded my kernel via serial port, because I never got u-boot to activate my ethernet (I never got the link led on, only after booting Linux).

I recently read the FAQ again and found about using valid MAC addresses:

* Should I recompile my u-boot with the new local-admin MAC address or just I need to write the new config on the board?

Thanks.