How to find out the Default Gateway from the first router?

Question

Computer networks

1. At the entrance there is a cable from the Internet - the cable is connected to the router
2. The Internet cable is scattered around the rooms, already with the Internet from the router above.
3. In one of the rooms, another router2 is connected to the cable.
The task is to set a static address on the first router so that the second one immediately receives a static address from router1 automatically.
To set the settings (static address) in router 1, you need information about the Default Gateway
How to find out the Default Gateway from router 1?
It is not possible to connect a PC / laptop to router 1, it is possible to connect to WI-FI of Router 1, but when connected, it shows the main gateway that it does not want to accept in its settings, and writes:
Error code: 5007
Bad Gateway for WAN IP, please input another one.
In short, you need to make a static address, while having two routers in a bunch

Answer 1

Connecting a PC / laptop to a router1 is not possible

There is web access.

Default Gateway

tracert

Answer 2

what prevents you from looking at the default gateway in the wifi / lan information of a PC or laptop?
What prevents you from entering the wan settings and setting everything automatically
Then put at the end the ip of the device that is not included in the dhcp range?
What prevents you from reserving ip on the first router at the mac address of the second router?
What prevents routers from connecting lan to lan?
Why can't you explain more clearly what you can't do there

It is not possible to connect a PC / laptop to router 1, it is possible to connect to WI-FI Router 1, but when connected, it shows the main gateway that it does not want to accept in its settings

To get access to the router, just
Open the browser, enter the main gateway (which can be found in the information)
Enter the login and password to access the gui settings
PS First, we would like to understand why you need to connect 2 routers in your home network, do you need to make a common wifi than automatic the definition of the settings did not suit and then the community will be able to find the optimal solution