Final answer:
When first configuring Marketing Cloud, it is recommended to whitelist the entire set of IP ranges for your region and the IP ranges of frequent users and administrators. This ensures secure access to the platform.
Step-by-step explanation:
When first configuring Marketing Cloud (MC), it is important to determine which IPs should be whitelisted for security reasons. The best practice is to whitelist the entire set of IP ranges for your region. This ensures that all users within your region can access MC. Additionally, you should whitelist the IP ranges of your frequent Marketing Cloud users and administrators and Marketing Cloud Support to provide them with easy access to the platform.