Okay, it's a bit of a long shot, but I have a Fortigate 600c at home running FortiOS 5.6. All licenses for Forticare IPS etc have expired. I have SD-WAN enabled, Virtual IPs configured for my locally hosted websites and server connections. Everything appears to be working fine. I can connect from any device to the internet.
However, everything is not fine because my flatmate cannot connect to specific game servers from his XBox One. When I say specific game servers, anything EA, XBox 360 or Activision. All other game servers he can connect to and use online features.
I have VIPs configured to set Open NAT Type.
If I swap the Fortigate out for the ISPs stupid little router (uPNP disabled), he is able to connect perfectly fine (though NAT Type is moderate).
I also seem to be getting a lot of "Failed Connection Attempts" being logged in the Fortigate which do appear to relate to these game servers.
Can anyone suggest anything that could cause this scenario?