What is required to ensure proper API access from an on-premises environment to Google Cloud APIs?

Ensuring proper API access from an on-premises environment to Google Cloud APIs involves securing the communication channels and managing access permissions effectively. The most appropriate method to achieve this is by setting up private access using restricted.googleapis.com domains.

When establishing a connection from an on-premises system to Google Cloud APIs, it’s essential to control how this access occurs to maintain data privacy and security. By configuring private access, an organization can leverage Google's private network for API calls rather than exposing the data to the public internet. This enhances security by minimizing the risk of data interception or exposure to unauthorized entities.

Additionally, using restricted.googleapis.com ensures that the API calls remain within Google’s network infrastructure, which enhances both performance and security because there's less external traffic that can potentially be compromised. This setup is particularly important for organizations handling sensitive data or those that need to comply with various regulatory standards regarding data protection.

The other options do not specifically address the direct need for securing API access between an on-premises environment and Google Cloud APIs. Configuring external DNS settings pertains more to domain name resolution, and while the gcloud SDK might assist with API management, it does not inherently secure access. Establishing public key encryption is more related to securing data transmission rather than controlling API access as