As an organization grows, more people have to log into the BIG-IP.

Comprehensive and Detailed Explanation From BIG-IP Administration Control Plane Administration documents:

BIG-IP supportsremote authenticationby integrating with centralized authentication services through its AAA framework. Thesupported and commonly used remote authentication serversinclude:

LDAP (A)Used to authenticate users against directory services such as Active Directory or other LDAP-compliant directories.

RADIUS (C)Commonly used for centralized authentication, authorization, and accounting, especially in network and security environments.

Why the other options are incorrect:

OAUTH (B)is an authorization framework, not supported as a direct administrative authentication backend for BIG-IP management access.

SAML (D)is primarily used forsingle sign-on (SSO)in application authentication scenarios, not for BIG-IP administrative login authentication.

Thus, the correct remote authentication server types areLDAP and RADIUS.