Configure nginx to accept connection from a single host/ip on specific subdomain

Question

I would like to know how to configure nginx to allow access to a single IP, for a subdomain.

Which means, all *.domain.com can be accessed by public, except dev-stg.domain.com

as you might have guessed, I am trying to reserve one subdomain for a pre-production check.

Answer 1

I would recommend using the geo module:

geo $unknown_ip {
    default 1;
    192.0.2.1 0;  # or use CIDR notation
}

server {
    listen 80;
    server_name example.com;

    location / {
        if ($unknown_ip) {
            return 403;
        }
        try_files $uri $uri/ =404;
    }
}