@JimmyLow 

Hello, thanks for posting in our community.

Can you please draw me a specific network layout when adding the Deco M9P as a secondary router in the network? Are the M9P and BE85 working in Router mode and connected to the Starhub 10Gbe nokia ont directly? Or is the M9P connected to the BE85 as a satellite unit?

Meanwhile, when you say 'by adjusting the QOS bandwidth that is allocated to the M9 seem to be able to affect the speed of the test result.', can I also confirm where you adjusted this QoS setting? On the BE85?

Enabling QoS helps you set priority for specific applications and devices through priority allocation and traffic management, especially in congested or high-load network conditions. It ensures critical applications or tasks receive more bandwidth and priority, but it doesn't equal setting a specific bandwidth for the client devices. So I assume it should not affect the speedtest results. We may need to investigate this further with more details.

@JimmyLow 

Thank you very much for sharing all the details about the network topo and QoS settings.

I have no idea why the QoS setting would affect the upload speed, but I will help escalate the case to our engineering team to further investigate this for you. They will contact you via your registered email here in the community, please check your email box later and discuss this with our engineers directly.