Global denial for certain IPs or agents?

[A. Schulze]

you could also include one file at all relevant places.

nginx.conf:
   server {
     # settings for server1
     include /path/to/include.file;
   }
   server {
     # settings for server2
     include /path/to/include.file;
   }

/path/to/include.file:
   allow from ip1;
   allow from cidr2;
   deny all;

Andreas