Hi @llama-for3ver 

Thanks for posting in our business forum.

llama-for3ver wrote

I have a setup as the following: Device > switch > modem. After adding the switch, I can no longer use port forwarding on my router on it, it just times out outside LAN. How do I fix this?

Switch is a layer 2-based device and it should not have any involvement in layer 3 IP and layer 4 port.

You should really examine the port forwarding rules and server with the guide from your modem vendor. Or try out the basic troubleshooting guide on our forum on the router page.