It was the privacy extension enabled on the windows hosts. So it was sending out from addresses the KVM HOST is not member of the multicast group. disabled it with netsh interface ipv6 set privacy state=disabled Stefan -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html