TACACS+ Authentication

How Authentication Operates

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.

Local Authentication Process

When the switch is configured to use TACACS+, it reverts to local authentica­ tion only if one of these two conditions exists:

■“Local” is the authentication option for the access method being used.

■TACACS+ is the primary authentication mode for the access method being used. However, the switch was unable to connect to any TACACS+ servers (or no servers were configured) AND Local is the secondary authentica­ tion mode being used.

(For a listing of authentication options, see table 4-2, “Primary/Secondary Authentication Table” on 4-16.)

For local authentication, the switch uses the operator-level and manager-level username/password set(s) previously configured locally on the switch. (These are the usernames and passwords you can configure using the CLI password command, the web browser interface, or the menu interface—which enables only local password configuration).

■If the operator at the requesting terminal correctly enters the username/ password pair for either access level, access is granted.

■If the username/password pair entered at the requesting terminal does not match either username/password pair previously configured locally in the switch, access is denied. In this case, the terminal is again prompted to enter a username/password pair. In the default configuration, the switch allows up to three attempts. If the requesting terminal exhausts the

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