I have two non-commercial home routers. Router A is a TP-Link AX1500 and Router B is a TP-Link AX1800. Router A is downstairs with its WAN interface connected to my modem. Router B's WAN interface is connected to Router A's LAN interface.
Router A's default gateway is assigned to the IP address of 192.168.0.1/24, and I have a DHCP reservation in Router A assigned for Router B as 192.168.0.100. Router B's default gateway is 192.168.1.0/24. Router B is currently running with DHCP enabled as I have a Raspberry Pi connected with a static IP of 192.168.1.101. The firewall is disabled on Router B.
From the Raspberry Pi, I can ping both Router B and Router A (192.168.1.1 and 192.168.0.1), however; from any device connected directly to Router A, I cannot ping my Pi. I attempted to configure the routing table of Router A with route 192.168.1.0/24 via 192.168.0.100, however; when I ping 192.168.1.101 I receive a host unreachable error. Therefore, I can ping upwards so to speak, but not downwards.
I am new to networking so I do not even know how to specify my problem, however; I think that I am trying to connect two subnets. I would like to make my Pi which is connected to Router B exposed to Router A such that I can configure port forwarding and make the device accessible over the internet. Of course, the easiest solution would be to relocate the Pi and directly connect it to Router A. This is unfortunately non-ideal for my setup for reasons I will not go into.
I have access to the configuration for both routers.