I've had this issue ever since upgrading to Internet 30. I've run statistics directly on my Xbox One and it says it's running about 4.2 Mbps up (as expected) but only 9.4 down, less than half what I should be getting. Packet loss is 3%, 1500 MTU, 36 ms latency and an open NAT. I use a cable to connect the box to the Internet, but when I connect it wirelessly it gives me 28 down.
Everything that connects to the Internet in the house goes through an Untangle gateway, but I've triple checked the settings on it and there's no issues there (there shouldn't be anyways, as my laptop/phone/tablet/everything else gets about 28 Mbps down, both wired and wireless). I've factory reset the Hitron but no luck there. I don't have any port forwarding set up. I've gone through Microsoft's troubleshooter on this topic, but the steps it's suggesting I take seem like overkill so I haven't done any of that. I haven't reset the Untangle - I don't think it's the problem here and like other Linux-type servers, it's designed to run without needing routine rebooting. I also tried plugging the Xbox directly into the Hitron (bypassing the Untangle) but the Xbox says it can't find a DHCP server and doesn't give me any connection at all.
As others have noted on this forum, I had trouble in the past with the Xbox One being on a strict NAT so I added it to the Hitron's DMZ, which solved that. When I reset the Hitron I added the Xbox to the DMZ again, but have made no other changes to the Hitron's settings.
My home was built with network ports in almost all rooms, so I make use of wired connections as well. I connected my laptop to the same cable the Xbox uses and no trouble there, so wiring doesn't look like the culprit. I disabled the wireless functions on the Hitron and have instead plugged in a Asus router into the living room to use as a wireless AP (so all wireless traffic goes through the Asus, then the Untangle). All DHCP and DNS are handled by the Hitron - the Untangle runs in transparent bridge mode and the Asus only serves as an AP, though I've given both of them static IP addresses. The network flows like this:
Wired devices + wireless devices via AP > Unmanaged switch > Untangle gateway > Hitron
Any ideas? My original intent was to connect the Xbox via cable only, so I'd still love to do that but I don't know why it's giving me so much grief when the wireless connection hums along just fine. I'll have Microsoft look at the Xbox if it comes to that, but I don't think the problem's with its wired adapter either.