HE160/HE80/HE40/HE20 mesh networking

Doesn't seem to be supported by OpenWrt stable right due to a limitation in the iw utility. Mesh nodes revert to VHT80 on 5 GHz and HT40/HT40 on 2.4 GHz.

Is there any workaround available?

Mesh is incompatible with DFS since all nodes are required to operate on a fixed channel. In DFS countries, there are no 160 MHz channels that don't require DFS compliance, as part of the bandwidth is in the DFS portion of the band.

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DFS is not the topic here. OpenWrt isn't able to use any HE modes at all for 802.11s mesh networking. Neither at 80 MHz or smaller channels widths, not even HE20 on 2.4 GHz. It's not properly supporting Wi-Fi 6 and I'm asking for workarounds, because the drivers probably do.

You are correct that DFS is not the topic here, but it can be an issue for 802.11s in general as @mk24 said.

The issue here is indeed the lack of support for HE modes in the iw utility, or at least its apparent lack of support.

The OpenWrt mac80211.sh library scripts use iw for setting up a mesh network, and there does not seem to be any way to specify HE modes in iw.

However, does the wireless driver actually use "Wifi 6" but iwinfo does not report it?

I do not know of a workaround yet, but of course a fix is possible, but it would need someone up to speed with the deep down driver related code to sort it out....

inwinfo is not iw, it seemingly supports reporting HE modes.

When I configure an AX 160 MHz mesh point on OpenWrt, inSSIDer reports another 80 MHz Wi-Fi 6 mesh point on top of the already running 160 MHz Wi-Fi 6 access point with half the data rate. iwinfo reports VHT80.

Downgrading OpenWrt config to AC gets me 160 MHz Wi-Fi 5 access point and an 80 MHz Wi-Fi 6 mesh point, while iwinfo still reports VHT80 for the mesh.

Same goes for 2.4 GHz, where iwinfo is reporting HT20 instead of HE20 for mesh point. On air the mesh looks like AX, but I have to confirm that.

So the driver is doing its own thing anyway, but I want to figure this out before I purchase more Wi-Fi 6 hardware intended for running OpenWrt.

Not on a mesh interface, as you pointed out later.

It is difficult to find out what the driver is doing, not least because both mesh and ax modes seem to confuse wireless analyser tools, at least all the ones I have tried so far.

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I guess iwinfo reports the driver configuration, not what the hardware actually does on air.

They are pretty consistent with what Wireshark reports. Currently I have no AX 160 MHz client for setting up mesh points to make sure that channel width and throughput matches expectations, there is only AX 80 MHz and AC 160 MHz client hardware available to test with.