Actually, you answered this way
[1] Exit connection
[2]'s exit] is equivalent to using the second router as a switch.
Before connecting, you can use one machine to connect to router No. 2 and check the instructions of the two routers. If their default IPs are the same, modify them.
[2] The intranet IP is fine. Fill in as you just use it as a switch.
Another method is what the second floor said, which can isolate the machines connected to different routers.
This is the method
[1] An outlet connection
[2] Entrance
For example, at this time, the ip of 1 is 192.168.1.1, you can change it
[2] The wan port is set to 192.168.1.254. The ip of the intranet of 2 is another network segment 192.168.0.1. At this time, the machine connected to 2 is only set to 192.168. The ip of the network segment can be pulled online.
[1] Exit connection
[2]'s exit] is equivalent to using the second router as a switch.
Before connecting, you can use one machine to connect to router No. 2 and check the instructions of the two routers. If their default IPs are the same, modify them.
[2] The intranet IP is fine. Fill in as you just use it as a switch.
Another method is what the second floor said, which can isolate the machines connected to different routers.
This is the method
[1] An outlet connection
[2] Entrance
For example, at this time, the ip of 1 is 192.168.1.1, you can change it
[2] The wan port is set to 192.168.1.254. The ip of the intranet of 2 is another network segment 192.168.0.1. At this time, the machine connected to 2 is only set to 192.168. The ip of the network segment can be pulled online.