Overview of Remote Authentication
The User Management feature manages all the tasks related to user authentication and authorization. The types of authentication and authorization are dependent on the device they are performed. If authentication and authorization are performed by the device itself, it is called local authentication. If authentication and authorization are performed on an authentication server such as a RADIUS server, it is called remote authentication.
Remote authentications work only if the user login credentials are stored on the authentication server and a connection exists between the device and the authentication server.
Local authentication is used by default.
Remote authentication supports RADIUS authentication and TACACS+ authentication. You can configure both remote authentication and local authentication for a device. However, the remote authentication takes precedence. Moreover, local authentication is attempted only when remote authentication fails.