Some APIs that implement server-to-server communication will authenticate using IP address whitelists. For this use case, we have the IP Consumer Auth module. Whitelisted IP addresses are controlled by a form that saves a configuration value.

If an IP address is whitelisted, the user is authenticated as an anonymous user. While this may not be recommended for POST, PATCH, and DELETE requests, it can provide a simple way to control specific GET endpoints in a private network.

You can download IP Consumer Auth from its project page at https://www.drupal.org/project/ip_consumer_auth.