Hello Stephan, > Bridging doesn't like loops, and you have created a loop. I agree. It was actually a Microsoft Load Balancing cluster that created the loop. Michael told me that the physical switch works because it: a) broadcasts b) sends it to both ports. > If you are goin to mess around using ebtables, just write another rule > to drop the reflections. Michael said that ebtables only after the bridge has seen the packets and so is not applicable. Is that true? So should I use arptables. I tried to block the looped packages by: - iptables - arptables - eptables But somehow I never made it. Do you have an example for me or can tell me which of the 3 tools should work, so that I can try again. The NATing fought the symptoms of my problem. Cheers, Thomas