What device are you using to test the connection speed? How far is it from the nearest deco unit?

Thanks for the reply. would using bridge mode really help? If yes, please guide me into how I can set the main deco9 to deal with ISP router as a bridge. I know the credentials given by ISP but I don't know how to setup the main deco.

Just got Deco M5. My internet subscription speed is 300Mbps down and 15Mbps up. I pluged the main M5 directly to modem.  However, when I tested with a Note 8 close to the main router, I only get 150/9. Even on a wired PC, I could not get 150/9. I prepared to return the Deco M5 set. 

 

One thing made me wondering is that if I test Internet speed with the Deco App, I could get 310/16. There must be something throttleing the speed on devices. I found I can set Bandwidth in QoS. So I set my bandwidth manually to 500Bbps down and 25Mbps up. Bingo, I can get 300/15 up now.

 

So, my conclusion is the QoS plays a load balancing role when testing speed on connected devices. The speed tested on router via QoS => Total Bandwidth is the real speed. There is nothing wrong with my router.

 

Hope my experience can help other users identify the issue.