Sorry, guys but this is so boring... So sure I have tested it with a real clean system (XP pro SP3 & Vista SP2 & Win7), and no gadgets/virus/firewall/QoS etc. B) And I know that no single speed programs is perfect! But all the speedtest programs on the marktet (including my exclusive provider for fiber-speedtest) give me a dramatically negative result and it's limit the bandwith dramatically! In practice, when downloading with IP-filtering is ON than the max download is about 12 Mbps. To all... Sure whit a simple Cable Internet abo (16Mbps Down / 2 Mbps Up), there is no problem at all. The max. speed is then about max. 15,xxMbps/1,9xMbps. B) But using my higer fiberspeed (60Mbps Down / 6 Mbps Up) and next month (120 Mbps Down /8 Mbps Up), there is still a big problem with this IP-Filtering option. So I don't use the IP-Filtering option any more.