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Fix bufferbloat on ASUS routers

Priority QoS only

Partly. Stock ASUS firmware has Adaptive QoS (priority) and Traditional QoS (speed limits). Asuswrt-Merlin adds CAKE, which is real Smart Queue.

Adaptive QoS sorts traffic into categories like gaming and streaming and lets the chosen ones go first. That helps a little, but the queue still fills when the line is busy. Traditional QoS limits the line to a speed you set, which is the part that stops bufferbloat. Asuswrt-Merlin, a free community firmware for many ASUS models, adds CAKE as a QoS type.

1. Test before you change anything

Run the Lag Check and note the "Lag under load" grade and your download and upload speeds. You'll compare against it afterwards.

2. Where the setting is

Stock ASUS firmware

  1. Open the router at router.asus.com (or 192.168.50.1) and go to Adaptive QoS → QoS.
  2. Turn on Enable QoS and choose Traditional QoS if your model offers it; it lets you set the upload and download bandwidth.
  3. Enter your speeds and apply. Adaptive QoS on its own also asks for bandwidth, but it's priority, not Smart Queue.
  4. Menus differ between models and firmware versions, so the tab may be called QoS or Bandwidth.

Asuswrt-Merlin

  1. Check your model is supported on the Asuswrt-Merlin site and install it like a normal firmware update.
  2. Go to Adaptive QoS → QoS, turn on QoS and choose Cake as the QoS type.
  3. Enter your download and upload speeds and apply.

3. The numbers to enter

ASUS asks for Mb/s. Start at about 90% of your measured speed, or use the figures from the Smart Queue assistant.

Work out my limits

The assistant starts at 90% of your measured speed and tells you when to drop to 85% or 80%.

Gotchas

  • On most ASUS routers, turning on QoS turns off NAT acceleration, so fast lines lose some top speed. That's expected: it's what lets the queue work.
  • Smart Queue runs on the router's CPU. Cheap routers often top out somewhere around 300 to 500 Mbps with it on; above that the shaped speed drops well below your limit. On fast plans that can be worth it for lag, or a sign you need stronger hardware.
  • If Adaptive QoS is all your model has and the grade stays at C or worse, it isn't enough. Merlin (if supported) or a CAKE-capable router is the real fix.

No real Smart Queue? Your options

  • Install Asuswrt-Merlin if your model is supported and use CAKE.
  • Put a Smart Queue router between your modem (or ISP box) and this system. A GL.iNet travel or home router running its built-in OpenWrt, or any router that runs OpenWrt, can do CAKE for well under the price of a new mesh.

Test after the change. A good setup brings lag under load down to A or B.

Test before and after