[GL-AR750] No connection between devices connected to LAN ports

Hi,

so I'm sitting in front of a GL-AR750 with Firmware 4.3.18 and I'm pulling my hairs out, honestly.

I did a reset of the router via the web intererface -> System -> Reset firmware to make sure I'm in a clean state.

I have two devices connected to the router via the LAN ports (the WAN port is not connected).

I can connect to the router from both devices.

I can ping both devices from the router (after connecting to the router via SSH).

I can ping the router from both devices.

I can NOT get a SSH connection between the two devices.

I can NOT send a ping between the two devices, no matter the direction.

What is going on here?

I did not change anything on the router after the reset, the only thing I did was set a password for the web interface.

Thanks already!

What IP addresses do they have? DHCP enabled?

Yeah, IP addresses are assigned via DHCP in 192.168.8.0/24.
If I connect one of the devices via WiFi, it works just as expected.
It's only an issue when both are connected via LAN ports.

edit: It also works fine if I reconfigure the WAN-port as LAN-port and plug one of the devices into the WAN-port.

So, I contacted support regarding this issue and they confirmed it.

They also provided me with a solution which I'll share here, should anyone else need it:

  1. ssh into the router (ssh root@192.168.8.1)
  2. edit /etc/config/network with your favorite text editor
  3. make the following changes