How to configure Nginx to limit the number of concurrent connections per IP address?

To configure Nginx to limit the number of concurrent connections per IP address, you can follow these steps:

Open the Nginx configuration file. The default location is usually /etc/nginx/nginx.conf, but it can vary depending on your system configuration.
Inside the http block, add the following code to define a limit zone and set the maximum number of connections:

http {
    ...
    limit_conn_zone $binary_remote_addr zone=conlimit:10m;
    limit_conn conlimit 5;
    ...
}

In the above example, we define a limit zone named conlimit using the $binary_remote_addr variable, which will store the IP addresses and their connection counts. The 10m specifies the maximum memory size for the limit zone. The limit_conn conlimit 5; sets the maximum number of concurrent connections per IP address to 5.

Save the configuration file and exit the editor.
Test the configuration file to make sure there are no syntax errors:

$ nginx -t

If the configuration file test is successful, reload Nginx for the changes to take effect:

$ systemctl reload nginx

With these configuration changes, Nginx will limit the number of concurrent connections per IP address to 5. You can adjust the values according to your requirements.