# Default elements for user authentication

There are predefined Authentication Method elements for user authentication on the engine and for external user authentication.

There are four predefined Authentication Method elements for user authentication on the engine.

- Client Certificate is for certificate-based authentication.
- LDAP Authentication is for simple password authentication against LDAP databases on external LDAP or Active Directory servers.
- Pre-Shared Key Method is for use with some third-party VPN clients.
- User Password is for simple password authentication against the internal LDAP database, including user authentication in Forcepoint VPN Client hybrid authentication.

To use the engine for user authentication, you must use one of the predefined Authentication Method elements.

There are three predefined Authentication Method elements for use with RADIUS Authentication Server or TACACS+ Authentication Server elements.

- Network Policy Server is for use with an external Network Policy Server (NPS) server.
- Pre-Shared Key Method is for use with some third-party VPN clients.
- User Password is for simple password authentication against the internal LDAP database.