ASUS RT-N66U 200 Mb Fiber sporadically capping at 115 Mb? ISP says all fine

[Kusuri]

Hello,

I've recently upgraded to a 200mbps download/100mbps upload fiber service and the first problem I had was that my download speeds were capped at around 120mbps with old original Asus firmware.

I've updated to Merlin's 380.57 firmware (380.58 has a bug in the IPTV section and I cannot properly input the necessary VLAN for my setup there) and the problem was solved (thanks to the NAT Acceleration CTF option set to Auto), I finally did get 200mbps download speeds when testing then.
QoS is OFF.

Just in case I've made a habit of testing the speeds now and then and over the course of the last 3 weeks and I've had 2 odd cases in which my download speed wouldn't go over 115-116 mbps (upload staying unchanged at 100mbps) until I decided to take some kind of action.
- The first time I did a full reboot of the router and it solved the problem.
- The second time I've decided to try something different and simply pressed the globe icon on the router's main page and turned the Internet Connection switch Off/On to refresh WAN Connection, obtaining a new IP. This also fixed it.

These seem random so far, had it happen both at lunch time and the other at midnight. The second time it was actually right after a successful 200mbps test. From then onwards always 115mbps until reboot.

I've contacted my ISP and they've said everything has been fine on their end, so I'm lost to the point I'm considering replacing the router, but not until I'm at least 99% sure it's the culprit...

Does anyone have any ideas on what could be causing such behavior and what I could try the next time this happens to help finding the source of this oddity?

Thank you kindly for any input

 

[Deepcuts]

How did you test your bandwidth? Using speedtest.net?
If so, have you tried another server? Maybe your ISP provides a test server for speedtest.net.
Also, having Kaspersky AV usually means slower speeds, even if disabled.
Anyway, shooting in the dark here. Some details for your testing procedure would be nice.

 

[Kusuri]

Hello Deepcuts, indeed you're right, I should've mentioned I used speedtest.net and yes my ISP has provided me with their own speedtest.net server when I called them. I still had it capped.

I also do have Kaspersky AV, the simple one without Internet Security, for what it's worth.
Perhaps I should test on an old laptop that has just the free Avast installed... and while I'm at it I could do a connection test on the PS4 and see if it ever goes over 115Mbps. I'm unsure but I think I forgot to test other devices besides my desktop PC when I had the speed capped.

Thanks for your input, always open for more.

 

[sfx2000]

please move this to the appropriate ASUS forum