AT&T: Port forwarding

Port Forwarding doesn´t help

you can´t use both UPnP and Port Forward.

Be sure that you only run 1 option.

UPnP OR Port Forward OR DMZ. A home Router can´t handle more than 1 option and then disconnects like you describe.

Delet all Port Forwarding and DMZ and leave UPnP enabled. Then Restart your Router - so the Ports get cleard. Problem should be solved then.

AT&T (ISPs): how to port forward my xbox one
This site is really useful in walking you thru how to forward your ports. https://portforward.com/

the Problem is: if you have more xboxes than 1 you only can use UPnP - this is the only way I know how it´s possible t get open NAT for multiple xboxes.

Be sure you run the latest Firmware for your Router and then enable UPnP and disable all Port Forwarding or DMZ. If UPnP is not secure enough for you then:

If you want to try Port Forwarding with 2 xboxes (not more) some people say you have to Port Forward Port 3074 TCP AND UDP to xbox 1 (static IP Adress) and the Port 3075 TCP AND UDP to the second xbox (also static IP Adress). It seems that xbox live uses
Port 3074 and if this Port can´t be used they use 3075. NO other Port should be Forwarded !

if you know how to forward ports you don´t need to choose both. You can choose TCP and then the same entry with UDP.

you need to forward this ports:

Port 88 (UDP)

Port 3074 (UDP und TCP)

Port 53 (UDP und TCP) (it´s only outgoing needed so no nedd to forward)

Port 80 (TCP) (only outgoing needed - so also no need to forward)

Port 500 (UDP)

UDP Port 3544 (UDP)

UDP Port 4500 (UDP)

be sure you forward them to the IP of your xbox. Your NAT should then be open.