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.