- Each client (laptop) needs to have a route to the other network, usually there's just a default gateway - in this case this must be
- The router gw-test needs to route between the networks. Since there's only a single router and both networks are directly attached, there's no need for setting static routes or using a routing protocol (which exchanges routes between routers).
- The network
172.16.0.0(/16?) cannot be used between the networks because both subnets belong to this network.
- The dotted link in the diagram makes no sense unless you separate both networks/subnets into VLANs and use VLAN trunks between the switches and to the router.