How to open access from one subnet to another?

Question

System administration

Hello. There is a main router with subnet 0.1. The second router is connected via the WAN port to the switch. Subnet of the second router 1.1. From the second router there is access to subnet 0.1, everything is pinged and everything is ok. From the first router there is no access to the second subnet, there is no ping, IP Scanner sees only the router itself. What do I need to do / configure in order to access the subnet of the second router from the first one?

Answer 1

Disable the firewall on the WAN port on the router with ip 1.1
Or allow any traffic INCOMING to this port

Answer 2

There are 2 options for access between networks.
1. Routing. Requires prescribed routes between networks on all devices in these networks.
2. NAT. Does not require routes on each device, since the router replaces source addresses on subnets with its originating address on the home subnet of the destination address.

Answer 3

implement the third option. Turn off dhcp on the second router, connect it with a LAN port. There will be one network, and no headaches with routing and firewalls.