TACACS+ Authentication

Configuring TACACS+ on the Switch

Figure 4-6. Using a TACACS+ Server for Authentication

Using figure 4-6,above, after either switch detects an operator’s logon request from a remote or directly connected terminal, the following events occur:

1.The switch queries the first-choice TACACS+ server for authentication of the request.

•If the switch does not receive a response from the first-choice TACACS+ server, it attempts to query a secondary server. If the switch does not receive a response from any TACACS+ server, then it uses its own local username/password pairs to authenti- cate the logon request. (See “Local Authentication Process” on page 4-22.)

•If a TACACS+ server recognizes the switch, it forwards a user- name prompt to the requesting terminal via the switch.

2.When the requesting terminal responds to the prompt with a username, the switch forwards it to the TACACS+ server.

3.After the server receives the username input, the requesting terminal receives a password prompt from the server via the switch.

4.When the requesting terminal responds to the prompt with a password, the switch forwards it to the TACACS+ server and one of the following actions occurs:

•If the username/password pair received from the requesting terminal matches a username/password pair previously stored in the server, then the server passes access permission through the switch to the terminal.

•If the username/password pair entered at the requesting terminal does not match a username/password pair previously stored in the server, access is denied. In this case, the terminal is again prompted to enter a username and repeat steps 2 through 4. In the default configuration, the switch allows up to three attempts to authenticate a login session. If the requesting terminal exhausts the attempt limit without a successful TACACS+ authentication, the login session is terminated and the operator at the requesting terminal must initiate a new session before trying again.

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