So I've spent the better part of the past week in an attempt to get a clean, open NAT for my Xbox One. It initially was almost constantly showing up as "strict" with the MP test describing the network as being "behind a port preserving, port symmetric NAT". I've since bought a new router (and the problems persisted initially) and had my ISP bridge my DSL modem to avoid whatever double NAT issues may have been present. Now the NAT shows up as "open" when I run the connection test, but when I do the MP test and then hit the shoulder buttons for the specifics, it still says it's behind a "cone NAT". The main symptom I seem to be encountering is no incoming sound from the majority of other players when I'm playing something on Live. I'll see the name and mic pop up that indicate someone is talking, but there's no sound through to my headset. I'll have a few people's voice that comes through, but others in the same session give nothing.
I've tried every trick in the book. Forwarding ports, no good. Always get a "port not open or reachable" message when I try the port check tool.
uPnP enabled/disabled hasn't seemed to make a noteworthy difference.
Putting the Xbox in the DMZ hasn't seemed to do much, either. It sometimes seems OK, but then the same issues reappear.
There's one "enable NAT" setting in my router that is checked as on, but if I disable it, I'm unable to connect to the internet at all. I'm not sure if that's the final thing i need to find a workaround for, or if I'm just getting some bizarre conflict.
My router is an Asus RT-N66R (from what I've gathered, it's largely identical to an RT-N66U). If anyone has any experience with similar issues, some advice would be appreciated. I'm at my wits end with this, and I'm hoping there's some dumb, simple solution that I've overlooked to this point. Thanks in advance.