Allow wired client access to WAN but block access to LAN
I recently had to provide an internet connection to my PV Solar Panel system inverter (SolarEdge brand) to allow system monitoring. It had previously used a 2G cellular data connection through T-Mobile, but with T-Mobile shutting down its 2G network, the inverter needed a different internet connection. The inverter has an ethernet port, so the simplest solution was to use an ethernet patch cord between the inverter and my Archer C9 router.
The inverter only needs the internet connection to allow my PV system's performance to be monitored via a website and app. There is no need for the inverter to communicate with or have access to any other clients on my home network.
Is there a way to allow a client hard wired to my router access to the WAN while blocking access to my LAN?
There's no mechanism for isolating a directly connected device through the router ethernet port from its LAN.
You could use a travel router like TL-WR902AC in client mode and connect it to the C9 guest wi-fi network, but I don't think that's worth the effort:
Don't know if you have the same features as me ( AX72 EU)
But on my tether app if I go into my client list and select a client from the client page.
I'm greeted with the option of device isolation,
If I click on the device isolation option it then gives me the next page as shown.
If I read your post correctly that in theory should solve your issue
I had the same options on wireless and wired devices on my client list if you have this option then that should solve your problem as you described it to not need to talk with anything on your home network but be connected to the WAN and work with apps 👍🏻