ASUS Router with BT Fiber not getting full speed

[Crimliar]

For the original OP, you've never lost those 200Mbps!  The way the Ookla Speedtest is implemented in the Asus WEB-UI is CPU intensive, and all but the latest top-end Asus routers don't have a powerful enough CPU to generate an accurate result.  You can see multiple discussions on this on https://snbforums.com

[Dal2]

Use ping to determine the correct MTU size to get the optimal speed for your own router. i.e

ping -l 1200 -f 8.8.4.4

Change the -l buffer size until you get the message "Packet needs to be fragmented but DF set."

The highest -l value where you receive a "Reply from 8.8.4.4:....." message is you correct MTU to use. You will need to add 28 (header) to the value.

[Col8]

I changed my settings and it really helped.

https://youtu.be/PBqJRb0rbqo

[willinliv]

Thanks guys for the suggestions re setting the MTU. The default on my router (RT-AC86U) is 1492 (stock firmware). I went through a few ping tests and determined I could get 1464 ok (1465 gave losses). Adding 28 took me back up to 1492 so did not need to change. However the internet on my PC with the longest ethernet cable is now reporting speeds of about 550Mbps that match the Asus's Ookla test. So fingers crossed this is just some teething to get things right. Thanks again, Will

[Col8]

What speed did you buy from buy from BT

[willinliv]

500

[flycop2000]

I am currently using the RT-AX88U-Pro and previously used the RT-AX88U. I have used both the Asus and Merlin firmware on both routers and there was difference in download/upload speeds.

I'm on a 500Mbps package and get:

473Mbps down

93Mbps up

There was no settling down period, I got these speeds from day 1.