OpenWRT "Repeater" with multiple SSIDs/VLANs

Installing and Using OpenWrt Network and Wireless Configuration
1

I am currently using OpenWRT on a device that is configured as a Dumb AP. Behind it, there's a router running OPNsense. I have two completely separate VLANs: one for "Home" and one for "Guest." Each of these networks has its own SSID on the AP.

To extend the Wi-Fi range, I now want to use another device with OpenWRT. This device should be connected via a wireless backhaul (unfortunately, using LAN cables is not an option) and should also broadcast both SSIDs from the two VLANs.

If I didn't have this requirement with the two VLANs, I would simply configure WDS, but I don't know if or how that would work with VLANs. I have found some posts suggesting that VXLAN tunnels could be used, but I have no idea how to set that up. In this blog post (https://badgateway.qc.to/vlans-and-wifi/), GRE is used, and an extra SSID is utilized for communication between the Wi-Fi APs. Is this the right approach? I am grateful for any suggestions.

2

Depending on the hardware, it is possible to connect as a client to multiple SSIDs at the same time. You can check the capabilities using the iw command:

root@OpenWrt:~# iw phy0 info
[…]
	valid interface combinations:
		 * #{ IBSS } <= 1, #{ AP, mesh point } <= 16, #{ managed } <= 19,
		   total <= 19, #channels <= 1, STA/AP BI must match, radar detect widths: { 20 MHz (no HT), 20 MHz, 40 MHz, 80 MHz, 160 MHz }
[…]

"managed" specifies the number of possible client connections. But you'll need to try if it actually works reliably.