Setting up a second router to be a separate network on a home networking router

Solution 1:

I understand this question is a few years old, but it still pops as first result on google searches, so here is the most direct route for what the asker was trying to achieve.

Modem -> WAN on Router A

LAN on Router A -> WAN on Router B.

Router A configured with a DHCP pool of 192.168.1.1/24

Router B configured with WAN port at an IP in the 192.168.1.x range (or just set to receive dynamically), and a DHCP pool on the LAN side of 192.168.2.1/24.

Solution 2:

When a packet from router 1's client, let’s say from 192.168.1.5/24 wants to send a packet to a client on router 2, let’s say 192.168.2.5/24 it simply cannot.

Routers that we use at home would send a packet that is addressed to a client in different subnet to the gateway and in this case it would be 192.168.1.1.

Little does router 1 know the presence of 192.168.2.0/24 unless your router supports routing; either static or some routing algorithm.

If it does then the routing table in router 1 should have an entry for 192.168.2.0/24 and the port that can be used to reach it.