the message of "No USRP2 found" doesn't mean anything

Although I do not know why find_usrps does not find anything, even if I specify the network interface as "-e ethX", usrp2_fft.py runs alright on "-e ethX".

I have gone through almost all the posts returned at the inquiry of "No USRP2 found", "Raw Ethernet", etc. None of them mentioned that IT DOESN'T MATTER...