@Xsanchi 

Thanks a lot for feedback.

After checking with the senior engineers, the port range under bandwidth control has no relation with the port forwarding setting.

The reason for this issue might be that the port used for speedtest packets(For your case, it might be port 443) is not included in the port range so that it is not under the control.

Based on your test:

Port 1-27038,  nearly 2m/s

Port 27000-27038, nearly 16m/s

Port 443-27038, nearly 2m/s

Port 444-27038,nearly 16 m/s

So you could try to test on the computer whether port 443 is used to transfer the speed test packets.

@Xsanchi 

Hi, Sorry for the port forwarding part.

I think you need to open ports 27000-27038 in order to access the streaming games.

As for the port range, it is quite like, we are able to test the speed of the router because router communicates with the speed test server via port 443.

If the port range under bandwidth included port 443, the communication would be limited and not all packets went through, so the speed is about 2m/s.

White if 443 not included, the communication is on the full speed-16m/s.

The port used to communicate with speed-test server, is not always port 443.

For example, when I tested on my side via Archer VR2100, the communication port is 8080.

So if I set port range to be 1----8080 or more, the speed would be limited to 2m/s;

While if port range is 8081-----25565 or less,  it is on full speed -16m/s.

In this way, the port for Archer D50 might also be another one(for example 27001) so when you tested with 27000-27038, you did not have the same issue.