How to test Bit Error Rates on Ethernet Networks?
Solution 1:
Ethernet frames are checksummed by a CRC, which is computed frame by frame. So you can't detect individual bit errors, you only know that a frame has a bad CRC.
Solution 2:
If you're running *NIX you can check /proc/net/dev to see stats about errors. It's vague about what errors, but according to this post on Stackoverflow it does record CRC errors.