Hi
You need to port forward the following ports to the Xbox LAN IP address (use a manually entered static IP address not an automatically assigned DHCP IP address).
53, 80, 88,500,1863, 3074, 3544, 4500
I would not worry too much about 53, 80, 88 and 500

Login to the ER5120 and go to Adanced - NAT - Virtual Server.
Type in Xbox1863 for the name
Type in 1863 for the internal and external ports (four places)
Enter the Internal Server Address (Xbox IP address)
Select Activate and then click on Save.
repeat for 3074, 3544 and 4500

regards
Steve

Thanks. I know about pretty much all of them ports apart from 1863. I will try but I don't hold out much hope. I have even tried DMZ without any joy. I also now have an official support response from TP-Link stating below:-

This is Tom from TP-link Support Center, I have received the issue from my colleague joy. Sorry for the inconvenience.

The ER5120 is a symmetric NAT, it does not support multi-player game console . And the problem can not be solved by Virtual Server, UPnP or DMZ as well because the the inside port and outside port are not the same in the port mapping of the symmetric NAT.

Maybe you can solve your problem by changing your network topology to bypass the NAT devices. You can try to dial up in the front modem and connect your Xbox to the modem directly. Or you can try our product R480T+ or R470T+ which can perfectly support Xbox one and other multi-player game console.

Please let me know if you have any other questions.

Best Regards
---------------------------
Tom.wu
Technical Support Engineer


The irony is that my Xbox 360, using just UPNP alone, shows open NAT. So someone, somewhere, is wrong!

Hi,
I have an Xbox360 and a PS4 - both are setup in this fashion and both can play Destiny online.
I am using two WAN links both of which use NAT addressing as well as the ER5120.

So try setting the ER5120 to use One2One NAT translation. This takes your LAN addresses such as 192.168.0.123 and translate them to 192.168.10.123 or what ever you have the ER5120 WAN interfaces set to.
You also need to setup the WAN cable/ADSL routers to Port Forward as well.

To see whats going on download and install WireShark onto a laptop and connect to a spare port on the ER5120.
Configure the ER5120 to port mirror to this port.
eg: ER5120 - Network - Switch - Port Mirror - Enable Mirroring,
If Port 1 & 2 are WAN and Port 3 spare, so set Port 3 to Mirror Ports 1& 2 Ingress and Egress.
Its easier if nothing else is running except for the XBox then you can see IP addresses and logical ports in use.

Hope that helps

Just to clarify you cannot set your Cable/ADSL router to port forward to the LAN address of the XBox because it does not know where that address is.

External IP -> Router -> interlink IP address -> ER5120 -> LAN IP address -> Xbox

Hence needing WireShark to see what is going on in the Interlink space.