00:aa:bb:01:23:45

Hello By accident I noticed several of my VPLS instances have 00:aa:bb:01:23:45 in the MAC table. We never sent anything just received a little traffic from that. Obviously not a real MAC address so I tried to search Google for it. I find several hits with apparently ADSL users doing pppd (which we do not have). Anyone have any idea what this could be? Regards, Baldur