Copy files between two Windows hosts in different subnets

Question

I have a laptop which resides in the main router (a Telekom Speedport) WiFi subnet 192.168.2.0 and another desktop machine sitting in a different subnet 192.168.90.0, that is created by a switch plugged into the Speedport.

Their respective gateways are 192.168.2.254 and 192.168.90.254, both bear the submask 255.255.255.0, indicating that they do not consider each other local.

WAN
|
Speedport - Wifi (192.168.2.0) - Host 1
|
Switch - Subnet (192.168.90.0) - Host 2

Is it possible to configure the routing on the Windows hosts that they can see each other by hostname or IP and exchange files or is that something I need to change in the Speedport router (or the switch or both) ? I tried setting the submask manually (to 255.255.0.0) for both hosts in their connection managers, but after that no internet connection worked at all.

Where do I need to change the configuration?

Answer 1

I assume your switch is a SOHO router, because otherwise this doesn't make any sense. Switches do not isolate subnets.

The missing piece is your second router will always drop unsolicited traffic arriving on its WAN port. Even if you added routes or adjusted subnet settings to drive 192.168.90.0/24 traffic to that router, this router's NAT firewall will not allow 192.168.2.0/24 machines to talk directly to 192.168.90.0/24 machines.

You need to set up port forwarding or Destination NAT rules on the inner router so that you can use that router's WAN IP address to reach the machines inside the network.

For example, I might forward port 445 for SMB to the machine in 192.168.90.0/24 I need to transfer files to. Then, from my 192.168.2.0/24 machine, I will put in the IP address of the router. The router will forward the traffic to the machine designated for port 445 and I can transfer files.