RT-AC88U broken WAN port or QOS problem?

[FabianZD]

Hello!

I have an RT-AC88U router with merlin fw 384.19, my internet connection is 200/10 mbps Cable DOCSIS. A few days ago my internet download speed drops from 200mbps to 20-25mbps so i call to my ISP to check the problem, they sent a guy to check the connections , modem and router and all the tests points to a problem with my router, if a computer is connected directly to the cable modem i got 200mbps but through the Asus router over the WAN port i got only 25mbps. As a workaround i enabled Dual WAN on the router and set the Port1 as primary WAN and everything work fine again (200mbps) so i was pretty sure that WAN port is fried, but i did not stop my tests there... back to the WAN port my downloads can't go higher than 25mbps but video streaming like 8k videos or simultaneous 4k videos plays smoothly, bandwidth monitor shows download bandwidth up to 150mbps while i im playing simultaneos videos, but if i tried with files or websites bandwith does not goes over 25mbps so i start thinking about a QOS problem.

I tried downgrading firmware, stock firmware, factory restore, clear NVRAM, turn off QOS, etc... and the results are always the same. Sometimes if i unplug and then plug again the cable to the WAN port i got 200mbps for less than a minute and then back to 25mbps (sometimes, not always).

What do you think? Broken WAN port or any other idea to try?

 

[dave14305]

On the main router page, what is the speed of the WAN physical connection?

 

[FabianZD]

Hi Dave14305... yes, the connection is reported as 1 Gbps Full Duplex

 

[FabianZD]

Check this out... Video Streaming from Youtube 80Mbps

But Speedtest only 21Mbps:

QOS is set to OFF

 

[alba666]

Same thing happened to me.
I needed to address signal quality issues on second floor anyway (plaster walls), so I made the AC88 an AiMesh node.
I got 4 years out of the AC88 as sole device, so anything additional use is gravy.