I bought my X1 Friday and spend some time in the single player mode of Horizon 2 but yesterday night i wanted to make my first races online but there is a problem connecting to the lobby. it says "unable to join, check internet connection and try again after searching on the internet i did see some things to change so i did:
You may not need to forward any ports to achieve Open NAT with your Xbox One.
I attempted to use my One with the modem/router that I used with my 360 for years and couldn’t figure out why I couldn’t achieve Open NAT with the same settings that allowed me to do so with my 360.
Got a new modem/gateway and as soon as I plugged it in and turned it on, I had Open NAT and it works perfectly. I didn’t have to forward any ports. I’ve been running it for a year and have had zero problems.