Which user authentication method is most suitable for a large number of users?

RADIUS (Remote Authentication Dial-In User Service) is particularly well-suited for environments with a large number of users due to its centralized authentication mechanism. This method allows for the effective management of user credentials by maintaining them on a dedicated server rather than on individual devices. As a result, RADIUS streamlines user access across various systems and services, facilitating integration with other security practices and protocols.

Additionally, RADIUS enables multi-factor authentication, which enhances security for a larger user base. It can also handle various user groups and policies, which is critical in larger organizations where different users may require different access levels. Moreover, by using RADIUS, organizations can easily scale user management as their needs grow, making it a robust option for high-volume user environments.

In contrast, approaches such as Local Database, LDAP, and Local Users generally involve more manual management and may not offer the same scalability and efficiency in user authentication as RADIUS, making them less suitable for handling large numbers of users.