The quickest and easiest way to sort this out is to put your console into a DMZ. To do this login to the router, goto advanced settings then dmz, choose a ip address eg 99, then click apply. Next goto address reservation then and assign your xbox one the same ip u put into DMZ, then click apply. Finally hard reset your console by pressing and holding the xbox logo on the front for 3 seconds until it beeps twice, then turn it back on, you should then have open NAT settings. Be advised putting your console into a DMZ means it is completely open to the internet so don't do any online banking through the web browser.