How does the geo module in nginx work?

Question

Nginx

Good afternoon! I started to study web servers, in particular nginx, I look at different settings and configs, but I didn’t understand the geo module, incl. according to official documentation. I saw this setting on one web server

geo $nonlocal_addr {
  default 1;

  192.168.0.0/16 0;
  172.16.0.0/12 0;
  10.0.0.0/8 0;
}

it is clear that local addresses are marked there, but what does 0 at the end mean?) well, in general, an educational program on geo would be very necessary
Thank you in advance

Answer 1

"Zero at the end" means the value of the variable, which is assigned if the IP address falls into the appropriate range. By default (if it does not hit) - one. This is how geo works.
I don’t even know what else to offer you besides documentation - it seems to be quite exhaustive ...