Sunday, November 20, 2022

TP-Link Deco M4 - Review / Bufferbloat / Reset


Of course, one should carefully consider the amount of trust one places in a Chinese company like TP-Link. In general, their hard and software seem to be reasonable for the price point, but privacy is a bit of a thing these days...

Anyway, in case you would decide to buy a mesh Wifi network, TP-Link has a cheap(er) product called the Deco M4. 


It's cheap enough to be handed out on loan base by Ziggo. For free.

If you buy the units yourself they go for around 100 bucks per 3 units, zo Ziggo probably pays round 20 to 25 euro for three. But hey, if your Wifi is poor (or your router quite old) it isn't the worst deal... three mesh routers for free? Why not?



I was still using a TP Link Archer C7 v5 (ground floor) and a v2 (top floor). My contract with my ISP Ziggo gives me 100/20 up/down (yeah, I'm a cheapskate, but what would I use anything faster for?) so these were fast enough. The M4's are about as fast, if perhaps even a tad faster. I don't know how they will perform under heavy load, but thus far they worked fine.

The port connected to my (bridged) modem is 1 Gb, and the M4 is fast enough to saturate the 100 Mb download. No issues there.

For more on Wan (ISP) speeds and the usefulness / uselessness of higher speeds, see here and here (Dutch).


Wifi, no matter what kind, is still crap compared with decent wired ethernet, so everything I could wire is wired to a 24 port 1 Gb ethernet switch, so I don't care too much about the ethernet speed of the Deco M4.

What still surprises me is that I can't find a Deco or similar product that includes a bunch of switch ports on the unit. The Deco units just have two ports.Why not build in a switch and expand the number of ports to 5 or 8? There's space enough, and most people would be willing to pay 5 bucks extra for that feature.

Then again, most people will just use these as Wifi range extenders, so perhaps it doesn't matter. But I would buy a unit with a few more ports, definitely!

What would be nice is a bit more clarity on port usage (activity leds), as well as a preassigned port (port 1) for WAN connectivity, just for security reasons.


Just 2.4 and 5 Ghz, but they both work fine. Range is a bit less than the old Archer C7's, but I now have three instead of two units, and that seems a fair trade-off.

If you use these units as non-cabled range extenders they will try to communicate with the home base (main Deco) over Wifi, thus throttling your connection. Wire these things!

(For Dutch users, read this.)

With the uplink wired, my tablet (a Samsung Tab S6 Lite) still reaches 90 Mbps at 5 metres distance, and 29 Mbps at 5 meters distance with a concrete floor in the way.


This thing has a WAN router build in, so if you have an old router you could get rid of it and replace it with a Deco M4.

Note though that feature wise this box is rather limited. No incoming VPN and only QoS. No indication of load, performance, or anything else. The software is a bit simple and barebone. Don't expect anything to fix your bufferbloat other than abusing QoS.


Using my standard test (measure loaded latency, always show) I reached 92/19. The max downspeed is 100, but yeah... bufferbloat heh?

Without QoS settings DSLreports gave me 103/20 with scores D / D.

With QoS settings I had the same results at first... turns out, the Deco M4 ignores the QoS settings unless there is at least one device added as a high priority device. Right... that's not documented anywhere.

Setting QoS to 100/20 down / up, adding my tablet as the only high priority device, then visiting on a PC gave me 98/18 down / up with scores A+ / A+.


Only through the app. No web interface, and that's a bummer. Also the layout of the app, even though it doesn't have that many options, is a little confusing.

Update. Yes. There is a web interface, but it's not mentioned anywhere. Weird. Anyway, the web interface offers a tidbit more information on memory and cpu load, but it doesn't allow you to set things like QoS or client names.


The main reason for this post (heh).

If you change configuration, the Deco or the app may sometimes hang on 'connected'. The only solution is to reset the box and reconfigure it. In general that's fairly easy as the process is fast and there is little to connect.

How to reset

1. Remove all ethernet cables

2. Switch off all other Deco units

3. Switch off and on the unit to reset

4. Led will be green first

5. Wait until the led starts flashing (any color), or turns white

6. Press the reset button at the bottom for 5 seconds (bring a paperclip or a small screwdriver)

7. The unit should start flashing green

8. Release the reset button, the unit's led should go steady green

9. Wait for the unit to start flashing blue

10. Start configuring again


Thus far they work fine, and I haven't seen any security exploits yet. Let's try this kit for a while and see if I keep this verdict or not...

Limited CPU

Note that these routers don't have a powerful CPU, and so they will fail or perform poorly on very heavy network traffic and / or fast WAN connections (high bandwidth ISPs). If you have a fast internet connection, you might want to keep your old router, and only use the Deco units as Wifi access points. You should use wired ethernet wherever you need real speed, and only use Wifi for small, mobile units, in which case the absolute speed may not matter that much.

Known (possible) issue(s)

Fast Roaming seems to trigger error messages and may cause intermittent hiccups, according to some sources on the Internet. A possible test is continuous pinging of the M4 routers, and see if the ping results are irregular.

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