OpenWrt for Zyxel WSM20 (Multy M1) development discussion

You may be running into this bug with 802.11s

If you use the same frequency, yes (and for most APs that means the same band). Think about it this way: if you want to connect to AP3, your actual connection might need to go through AP2, since the signal is too weak to reach AP1. That means that both AP1 and AP2 need to send the data at some point and they cannot do that at the same time, since they share the "medium" (frequency band) - thus the effective bandwidth is halved. In practice you have to deal with 'congestion' (figuring out who can send when) as well, and this gets worse the more APs you have trying to get their data out at the same time.

Your actual mesh "connection tree" might look different from what you have draw above: here a metric is used to figure out who is actually communicating with whom, and this can depend on things like error count, bandwidth, latency and hop count. I have no experience in that, maybe someone else here can help out?

You could read more about this at about pages 17ff at

One other option would also be the following: you add another AP. How can this improve things? You split the mesh: you add it next to AP2 (let's call it AP2a) and connect it to AP2 using Ethernet. Since it will sit right next to it, that should be possible. Then, you use a different frequency band for the connection AP2a and AP3. Now the connection router -> AP3 still involves 2 wifi links, but 2 different (need to be non-overlappting) frequency bands, and thus, can work in parallel.

It sounds as though you’re hitting some of the fundamental limits around meshing, which can never be as good as a wired setup.

That depends how mad you want to go. You could add four more WSM20 units as “point to point” connections using a non overlapping channel and remove the mesh.

You would then have AP1 connected with a short wire to AP1A, AP2 connected with short wires to AP2A and AP2B, and AP3 connected with a short wire to AP3B.

The “A” and “B” devices would be set up with different SSIDs and provide dedicated links between the existing access points, with the network being bridged across the links

I don’t recommend this setup. It’s complex, wasteful and will be a pain to set up manage and maintain. So my questions back are:

  1. Do you really need higher speeds from AP3? A real world 100Mbps is pretty fast for home use, especially if you can just move rooms temporarily for a big transfer.

  2. Is it really impossible to run an Ethernet cable for at least one of the gaps? You can put a lot of time, effort and money into improving the wireless connection, but it may be less effort to bite the bullet and wire things in.

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I want to use maximum 3 units, but before mesh I was using Powerline, with same speed of 100mbps, so I wanted to improve this situation with mesh, but maybe it's not possible, I hope that I can pass a cable into my wall, so I can solve the speed problem, in this case do you have any cheap router/access point compatible with openwrt? I should use WiFi from main router, then from my secondary AP, and use just as a Dumb AP

The WSM20 are one of the cheapest devices you can find and they work fine as pure APs.

On Amazon Italy 3 WSM20 70€ , but 1 costs 77€ and 2 94, that's why I asked for an alternative, if I use just 1 device I want to spend around 20/30€

Single units are currently £19.98 inc VAT on

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Shoot, I ordered one via eBuyer's eBay shop only on Tuesday for £24.64, today it's £22.05. Note the eBuyer eBay shop offers free delivery.
Excellent device.

It's nice if you post links/info when the device is cheaply available, but:

This is the development thread! This has absolutely nothing to do with development!

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Aye, but it also has nothing to do with operating or configuring the device, so encouraging people to acquire one seems to fit better here.

Point taken though. I'll enjoy my cheap devices when they arrive, with the help of this thread.

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Hi guys, I'm sorry if i'm bother you, but I can't find a way to restore stock firmware, on WSM20 page i found this, but I don't know where to find the original ".bin"

mtd write zyxel.bin Kernel2
echo -ne "\x02" | dd of=/dev/mtdblock7 count=1 bs=1 seek=4 conv=notrunc

Can you help me please?
Thank you

The WSM20 page also contains instructions how to obtain it: by capturing the upgrade URL during a real upgrade. I don't have access to my files right now, but I'm sure someeone else can provide you with either URL or file.

Maybe I figured out, thanks for the quick reply, appreciated!

It works!
If someone needs help to restore stock firmware, this is the procedure that I did.

cd /tmp
wget ""
mv "V1.00(ABZF.4)C0.bin" "zyxel.bin"
[ "$(md5sum zyxel.bin | awk '{print $1}')" == "b601f1ee260460e4107345003f82b7f4" ] && echo "Firmware check passed!" || echo "Firmware is corrupted, download it again!"
mtd write zyxel.bin Kernel2
echo -ne "\x02" | dd of=/dev/mtdblock7 count=1 bs=1 seek=4 conv=notrunc

I recommend running one command at a time, to check if it was successful.
If it says Firmware is corrupted, download it again! do again the wget.


This is sufficient to get back to the stock firmware. Does anyone have the URL for the current version 6, though? You can always flash 4 and upgrade to 6 later, but it would be nice to have the URL as well.

Can I ask why you want to restore stock? The consensus is that it’s pretty awful, so I’m interested to know what feature is missing from/not working in OpenWrt and is working in stock.

Yes, the stock firmware is terrible, but I had a lot of problems with wifi mesh / wifi ap, with cable it works very good, but I can't connect 3 devices with cable. (That's why I bought wifi mesh system)
I restored stock firmware because I decided to return them.

Thanks for posting the restore to factory process. I have recently "upgraded" mine to OpenWrt and had been trying to figure out how to get the firmware and revert the routers back to stock firmware in the event that I wanted to sell them in the future. I couldn't help wondering however, whether they would have more value being pre-installed with OpenWrt ...

Can I ask why you couldn't connect all three with cable? Was this a practical issue or a technical one? I presume you are referring to wiring them together with Ethernet which is what I am about to do and have already purchased the CAT6 for the purpose, hence my question. The mesh seems to work OK and I was able to get it up and running on either 2.4GHz or 5GHz, but haven't used it "in anger" yet. I guess there are multiple variables, including distance between nodes, types of wall in-between, contention etc which may impact the effectiveness of the mesh over WiFi.

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These units have a button on the back which, in the original firmware, controls the LEDs. Since I do not have the OEM firmware anymore one question to those that still do or still remember: does this control "only" the white LED in the front?

OpenWRT currently does not offer the same working "out-of-the-box" button. It is, however, not that difficult to add it to a working system. I did that for mine and it works: letting the button in the back control the front LED. I opened a pull request for openWRT: You do not have to wait until this (hopefully) gets approved. All you need to do is to replace the file /etc/rc.button/lights_toggle with the code in the pull request (direct link: No reboot necessary.

This can also serve as a starting point for more elaborate ideas. Happy hacking.

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