Recently I upgraded from home hub 4 (no issues with NAT or MTU) to the home hub 5. Since installing I have encountered a low MTU problem. I have tried port forwarding, UPnP settings and DMZ all to no avail. The NAT type will only stay open if I port forward but the MTU doesn't change no matter what settings I try. Any one with a home hub 5 experienced anything similar?? I don't think the solution can be too difficult seeing as the hub 4 worked fine with some tweaks to the settings. I have taken off the smart set up also.