How to set up the system?

Question

Debian

In general, there are two network cards, one is hooked up to the router, the second to the Internet, for example: if I enter 192.168.0.1 in the browser, then the connection request goes through map 1; if I enter a global address, then through interface 2. What means to use? It is desirable that the advice be about settings files and not utilities! I will also take advice on kernel programming, tell me which sources to pick, such as networking?

Answer 1

What means to use?

Routing tools must be used.
/etc/network/interfaces

Answer 2

Google always gives advice.
https://serveradmin.ru/nastroyka-seti-v-debian/