# User authentication methods

Authentication Method elements define the authentication method used by particular authentication servers, and by particular users and user groups.

The SMC supports many third-party authentication methods. You can integrate third-party authentication products with the SMC through the RADIUS and TACACS+ protocols.

The following authentication methods can be used:

- User passwords stored in internal or external LDAP databases.

  LDAP authentication is used for simple password authentication against external LDAP databases.

- Client certificates.
- Pre-shared keys (for use with some third-party VPN clients).
- External authentication provided by servers that support the TACACS+ (Terminal Access Controller Access Control System Plus) protocol.
- External authentication provided by servers that support the RADIUS (Remote Authentication Dial-in User Service) protocol.