IOS Authentication and Accounting
IOS supports two modes of system authentication: old-mode and new-mode. Old-mode uses a static, locally stored user table or Terminal Access Controller Access Control System (TACACS) for user authentication. TACACS (introduced in IOS version 10.0) is a security software suite that provides a configurable modular system for providing authentication, accounting, and authorization. The service is provided by running a service or process daemon on a Windows NT or UNIX system. The server stores the user authentication and authorization data, and logs user and system accounting events. There are three versions of TACACS supported by IOS:
TACACS (CiscoSecure 1.x)
Extended TACACS (available in old-mode and new-mode) ...