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Using Passwords and TACACS+ To Protect Against Unauthorized Access
TACACS+ Authentication for Central Control of Switch Access Security
Using Passwords and
TACACS+
Table 9-3. Primary/Secondary Authentication Table
Caution
Regarding the
Use of Local
for Login
Primary
Access
During local authentication (which uses passwords configured in the switch
instead of in a TACACS+ server), the switch grants read-only access if you
enter the Operator password, and read-write access if you enter the Manager
password. For example, if you configure authentication on the switch with
Telnet Login Primary as Local and Telnet Enable Primary as Tacacs, when you
attempt to Telnet to the switch, you will be prompted for a local password. If
you enter the switch’s local Manager password (or, if there is no local Manager
password configured in the switch) you can bypass the TACACS+ server
authentication for Telnet Enable Primary and go directly to read-write (Man-
ager) access. Thus, for either the Telnet or console access method, configuring
Login Primary for Local authentication while configuring Enable Primary for
TACACS+ authentication is not recommended, as it defeats the purpose of
using the TACACS+ authentication. If you want Enable Primary log-in
attempts to go to a TACACS+ server, then you should configure both Login
Primary and Enable Primary for Tacacs authentication instead of configuring
Login Primary to Local authentication.
Access Method and
Privilege Level
Authentication Options Effect on Access Attempts
Primary Secondary
Console — Login local none* Local username/password access only.
tacacs local If Tacacs+ server unavailable, uses local username/password access.
Console — Enable local none* Local username/password access only.
tacacs local If Tacacs+ server unavailable, uses local username/password access.
Telnet — Login local none* Local username/password access only.
tacacs local If Tacacs+ server unavailable, uses local username/password access.
tacacs none If Tacacs+ server unavailable, denies access.
Telnet — Enable local none* Local username/password access only.
tacacs local If Tacacs+ server unavailable, uses local username/password access.
tacacs none If Tacacs+ server unavailable, denies access.
*When "local" is the primary option, you can also select "local" as the secondary option. However, in this case, a secondary
"local" is meaningless because the switch has only one local level of username/password protection.