Have you faced a similar issue when configuring two routers connected to a mobile hotspot with the network address 192.168.177.0/24? The first router (R1) has an IP of 192.168.177.15, with eth1 configured for the network 10.10.1.0/24, while the second router (R2) has an IP of 192.168.177.1, with eth1 configured for the network 172.16.1.0/24. You've described the routes and firewall rules, and attached a diagram. However, you're unable to ping the eth1 interface of R2 from the eth1 interface of R1, though you can ping the opposite modem from either R1 or R2's eth1 interface. Do you have any insights into what might be causing this issue?