The LDAP proxy mode of TOTPRadius was introduced as a workaround for implementing 2FA access for systems without native support for multiple authentication sources. This works perfectly fine for organizations with full on-premises or hybrid Active Directory implementations where domain controllers can be accessed over the local network directly using LDAP protocol. But we are discovering more and more organizations moving to full cloud Azure AD implementation while keeping some services, such as VPN, on-premises. As the LDAP interface of Azure AD is not accessible directly, it was not possible to configure TOTPRadius to use Azure AD as its authentication source.
This is the reason we added a new feature, Azure AD Proxy, which will address this gap. Starting from v0.2.7, TOTPRadius can be configured to use Azure AD as the authentication source.