[SOLVED] Internet speed slowdown after changing the router

[Smartestdumbo]

So I have recently changed my router ( its spec is definitely better than my old one ), however, my downloading speed drastically decreases from 12mbps+ to 400kbps and I don't why ...
someone please help
Router: ASUS RT-AC68U
Connected to my pc with a LAN cable ( unchanged)

 

[Ralston18]

Does the download speed start at 12 mbps and then drop or does the speed vary up and down?

On your pc run "ipconfig /flushdns" without quotes via the Command Prompt.

For more information:

https://www.lifewire.com/what-is-a-dns-cache-817514

Determine if that helps or otherwise resolves the matter.

If not.....

What port are you using on the ASUS? Did you try another port?

Try another known working (at speed) LAN /Ethernet cable just to be sure that there is not some problem with the existing (original) cable.

Does the following User Manual link match your router? (Verify.)

https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AC68U/E14013_RT-AC68U_manual_v2.pdf

Work through Troubleshooting via Chapter 6, starting on physically numbered Page 99.