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Bottlenecks in Asus RT-AX88U

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I have an RT-AX88U running Merlin 388.1 managing a gigabit feed from a Motorola MB8600 cable modem. When I lit this up about a year ago, I was reasonably satisfied with the overall performance, expecting that my gigabit going in would find some bottlenecks. I saw reasonably consistent 600-700 Mbps on the built-in speed test and knew my cable provider's performance would vary. I got busy with other things and left it alone except for firmware updates.

A few weeks ago, I noticed that my desktop PC (on gig Ethernet) was running slow on a large download. After the download finished I ran a speed test on the PC and saw downlink results of under 400Mbps. I followed that up with the internal speed test on the RT-AX88U and found it fairly consistent with the PC results. As a semi-retired IT guy, I immediately assumed the cable feed was slow, mostly because of bad experience with Cable Internet and the fact that we never used routers with the potential to bottleneck (and if I did, I'd have someone's foot firmly implanted in my posterior)

So, I put my backup bandwidth online (25/6 VDSL from AT&T) and connected my desktop directly to the cable modem. My jaw hit the desk when I saw the speed test on the PC. Solid downlink that topped out at around 950Mbps, the maximum expected on gigabit ethernet. I switched back to the router with the modem connected and saw the same slow speeds as before. I went through the router and turned off everything that might cause a slow-down -- Trend, firewall, QoS, etc. and the Internal speed test popped up to around 900Mbps.

My cable feed is supposed to be "up to" 1200Mbps, so just to test that I set up a bonded pair between the modem and the AX88U. The results were shocking--consistently above 1000Mbps, with an occasional 1200! I checked the speed on the PC and it was consistently above 1100!

Then I enabled the services I'd killed earlier. It topped out at about 500. Trend and QoS were the biggest offenders.

So, here are some questions:

  1. Is this bottlenecking "normal" for this router?
  2. Is there any known workaround to improve this condition?
  3. I'd like to keep the bonded connection to the modem, but I don't want to give up the fallback to a second WAN (my backup bandwidth). Is there any way to do both on this router?
  4. Did I buy the wrong router for my purpose? If so, what would you recommend?


I knew you were going to mention Trend from the title alone. All the processing you're asking your router to do is bogging you down. It's generally okay at lower speeds but really does throttle a 1 gig connection.
this router OEM lie started in 2009 or even before when they introduced 1Gbit ports with 400Mhz week processors
in the past like for
Asus RT-N16 QoS was about up to 50Mbit
Asus AC68U when you used QoS speed drops to about 200Mbit
Top Asus routers like you have as you see are about 500Mbit

if you want more you need to go with miniPC with good processors and that meet requirements like
  • CPU should support AES-NI if you plan to use VPN
  • CPU must be powerful enough to route your internet traffic (depending on your connection requirements)
  • CPU should be 64bit Intel or AMD (you probably don't want 32-bit ARM CPUs)
  • RAM - you must have enough for the packages you want to run. (minimum 2GB)
  • NICs - LAN ports should be coming from Intel. OPNsense still doesn't perform great with Realtec Network Interfaces.
  • WiFi - OPNsense supports a very limited number of WiFi adapters. If you plan to use WiFi, get the right adapter.
I am using personaly HPE MS gen 8 with Xeon E3-1265Lv2, 16GB RAM with OPNsese and zenarmor firewall

you can just google what HW is available for OPNsense in your country etc.

OPNsesne is not the only choise you have pfSense that have better documentation but less updates and very powerful openWRT.

a lot a people will tell that QoS is not needed for 1Gbit and for normal users it is true but I see big difference when I am gaming MMORPG/ FPS because of https://www.waveform.com/tools/bufferbloat and without Shaper ("QoS" name for OPNsense) it is hard to get A+ result. It is showing how your HW behave under stress. For gaming internet speed is not important and you will be OK with 10Mbit but latency shall be below 30ms. Here how it is graded:
  • Less than 5 ms latency increase - A+
  • Less than 30 ms latency increase - A
  • Less than 60 ms latency increase - B
  • Less than 200 ms latency increase - C
  • Less than 400 ms latency increase - D
  • 400 ms or greater latency increase - F

  • Web Browsing:
    • Download speed > 2 Mbps
    • Upload speed > 100 Kbps
    • Latency < 500 ms
  • Audio Calls:
    • Download speed > 100 Kbps
    • Upload speed > 100 Kbps
    • 95th Percentile Latency < 400 ms
  • 4K Video Streaming:
    • Download speed > 25 Mbps
  • Video Conferencing:
    • Download speed > 10 Mbps
    • Upload speed > 5 Mbps
    • 95th Percentile Latency < 400 ms
  • Low Latency Gaming:
    • Download speed > 10 Mbps
    • Upload speed > 3 Mbps
    • 95th Percentile Latency < 40 ms
The like you can see you do not need 1Ggit :) and maybe you are OK with current router setup with QoS enable.
The like you can see you do not need 1Ggit :) and maybe you are OK with current router setup with QoS enable.

It's true that I could survive nicely on a great deal less bandwidth than I have now, although I'd get substantial pushback from my wife and daughter, who have become addicted to 4K streaming. I even considered dropping back from the 1200 Gbit tier when my initial contract ended. Strange though it may seem, dropping back to a lower tier would actually cost me More than the 1200 tier I'm on now. The biggest reason I went to this tier was the 40gig uplink speed. My backup bandwidth is a 25/6 VDSL, and when it was our only service and I was spending a lot of time online working on machines remotely, the slow uplink was killing me.

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