What's the reason behind preventing users from changing Wi-Fi channel in repeater mode?

Routers
1

TL;DR
After upgrading my Beryl GL-MT1300's firmware from 4.3.19 to 4.3.25 (released in March 2025), I noticed that I couldn't change the 5GHz Wi-Fi channel anymore while in repeater mode. What's the reason for not allowing this anymore ?

The full story
Yesterday I needed my Beryl GL-MT1300 for the first time in a few months, and after logging in it proposed to upgrade the firmware, from 4.3.19 to 4.3.25, which I did. After the upgrade, it became excruciatingly slow (pinging the Beryl from 1m away, I had around 700ms delay !). Web UI was hardly usable. Rebooting the device didn't help.

Applying "Reset firmware" solved the problem.
Note that it isn't a factory reset, because it didn't restore the firmware shipped with the device. It still was on 4.3.25 after doing the reset. But everything went back to normal (of course I had to redo all the config).

But I think I may have identified what caused the slow Wi-Fi after upgrading to 4.3.25.

I'm using it as a repeater. Back with 4.3.19, I changed the Wi-Fi 5GHz channel to 48, because I have a rather old Chromecast (NC2-6A5, around 2015) that can only connect to Wi-Fi 5GHz with a channel below 149.

Now, I noticed that 4.3.25 doesn't allow changing the Wi-Fi 5GHz channel anymore while in repeater mode. Upgrading from 4.3.19 to 4.3.25 with a custom channel may have caused that slowness.

Thus, my question : what's the reason for preventing us from modifying the Wi-Fi 5GHz channel in repeater mode in 4.3.25 ? (at least from the web UI, I think it's still possible to change it through CLI, or maybe even through LuCI, although I didn't try).

I ended up reverting to 4.3.19, to get my channel 48 back ! Now everything is back to normal and I can use my old Chromecast again. But I wasted 2 hours applying a firmware update, only to revert everything to how it was before.

1 Like
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Most Wi-Fi PHYs only support simultaneous operation on a single channel.
This means that both the AP and STA need to use the same channel.
In other words, when in repeater mode, and router connects to another Wi-Fi network, its own SSID must also operate on that same channel.

Reference: ArchWiki – Wireless client and software AP with a single Wi-Fi device

To prevent users from unintentionally changing configurations that could make it impossible to connect to Wi-Fi networks or SSIDs operating on different frequency bands or settings, we have implemented these restrictions.

2 Likes
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Many thanks for these clarifications. May I ask two additional questions :

1/ How come that in my case everything works flawlessly (fw 4.3.19), even though I forced a custom 5GHz channel (48) to accommodate my Chromecast ? Is it because I connect the router to the hotel's 2.4 GHz network (for the simple reason that the hotel doesn't have a 5GHz network), and I use the router's 5GHz network ? Incidentally, I have also disabled the router's 2.4GHz network, because all my devices support 5Ghz and I've decided to use only that and thus don't need the router's 2.4Ghz network.

In other words, your statement that

when in repeater mode, and router connects to another Wi-Fi network, its own SSID must also operate on that same channel.

is only valid in case both the hotel's network and the router's network operate on the same frequency (either 2.4GHz for both, or 5GHz for both). Am I right ?

2/ Do you know if with firmware 4.3.25 it's still possible to change the channel through SSH and/or through LuCI ?

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Yes, right.

We have only restricted modifications to SSIDs within the same frequency band (2.4 GHz or 5 GHz).
Therefore, if you are connected to the hotel’s 2.4 GHz Wi-Fi network, you should still be able to modify the channel of the 5 GHz SSID via the GL UI as shown below.

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It is also possible to modify the channel via SSH/Luci, as we have not applied restrictions there. However, as mentioned earlier, this may lead to certain issues.

7

You are absolutely right, my bad. I just upgraded to 4.3.25 again, to get to the bottom of this.

It appears my hotel has a 5GHz network after all, I wasn't aware of it :

  • Before the update, the router always automatically connected to the hotel's 2.4Ghz network, and the router's own 5GHz network (with a modified channel) worked just fine
  • After the update, the router automatically connects to the hotel's 5GHz network, thus the perturbations on the router's own 5GHz network with a modified channel (channel modification is indeed greyed out, but the modification had already been done before the update).

Forcing the router to use the hotel's 2.4GHz network fixed the problem.

Many thanks for your help