# Integrating external authentication services

An external authentication server can be any server that supports either the RADIUS or the TACACS+ protocol, including Microsoft Active Directory servers.

Active Directory Server, RADIUS Authentication Server, and TACACS+ Authentication Server elements define the settings necessary for connecting to an external authentication server.

Authentication Method elements define the allowed authentication methods for the server, or the servers that use a particular authentication method.

In addition to the server element configuration in the SMC Client, you must configure the external authentication server to allow the engines to use the authentication services.