A main router, then a second router which connects from its WAN port to a LAN port of the main router. This second router's goal is to establish a separated network for guest devices.
I disable the DHCP function of the second router, and set a static IP (which is different than the IP of the main router). For example if the main router is 184.108.40.206, then I would set second router to 220.127.116.11).
If guests connect to the second router via LAN or WiFI, would the guest's devices be able to "interact" with the devices connected to the WIFI of the main router? Could there be any kind of interaction on Layer 2 or 3?
Is it correct to connect the WAN port of the second router to a LAN of the main router, or should it be LAN to LAN?
If this setup does not fulfill the "separation" criteria, what changes are needed to achieve separated networks (using a two routers approach - without the need of VLANs)?