The ngx_stream_geoip_module module (1.11.3) creates variables with values depending on the client IP address, using the precompiled MaxMind databases.

When using the databases with IPv6 support, IPv4 addresses are looked up as IPv4-mapped IPv6 addresses.

This module is not built by default, it should be enabled with the --with-stream_geoip_module configuration parameter.

stream {
    geoip_country         GeoIP.dat;
    geoip_city            GeoLiteCity.dat;

    map $geoip_city_continent_code $nearest_server {
        default        example.com;
        EU          eu.example.com;
        NA          na.example.com;
        AS          as.example.com;
    }
   ...
}