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ACCESS AUTHENTICATION CONTROL COMMANDS
The TACACS / XTACACS / TACACS+ commands let you secure access to the switch using the TACACS / XTACACS /
TACACS+ protocols. When a user logs in to the switch or tries to access the administrator level privelege, he or she is prompted
for a password. If TACACS / XTACACS / TACACS+ authentication is enabled on the switch, it will contact a TACACS /
XTACACS / TACACS+ server to verify the user. If the user is verified, he or she is granted access to the switch.
There are currently three versions of the TACACS security protocol, each a separate entity. The switch’s software supports the
following versions of TACACS:
• TACACS (Terminal Access Controller Access Control System) —Provides password checking and authentication,
and notification of user actions for security purposes utilizing via one or more centralized TACACS servers, utilizing the UDP
protocol for packet transmission.
• Extended TACACS (XTACACS) — An extension of the TACACS protocol with the ability to provide more types of
authentication requests and more types of response condes than TACACS. This protocol also uses UDP to transmit packets.
• TACACS+ (Terminal Access Controller Access Control System plus) — Provides detailed access control for
authentication for network devices. TACACS+ is facilitated through Authentication commands via one or more centralized
servers. The TACACS+ protocol encrypts all traffic between the switch and the TACACS+ daemon, using the TCP protocol to
ensure reliable delivery
In order for the TACACS / XTACACS / TACACS+ security function to work properly, a TACACS / XTACACS / TACACS+
server must be configured on a device other than the switch, called a server host and it must include usernames and passwords
for authentication. When the user is prompted by the switch to enter usernames and passwords for authentication, the switch
contacts the TACACS / XTACACS / TACACS+ server to verify, and the server will respond with one of three messages:
A) The server verifies the username and password, and the user is granted normal user priviledges on the switch.
B) The server will not accept the username and password and the user is denied access to the switch.
C) The server doesn’t respond to the verification query. At this point, the switch receives the timeout from the server and
then moves to the next method of verification configured in the method list.
The switch has three built-in server groups, one for each of the TACACS, XTACACS and TACACS+ protocols. These built-in
server groups are used to authenticate users trying to access the switch. The users will set server hosts in a preferable order in
the built-in server group and when a user tries to gain acess to the switch, the switch will ask the first server host for
authentication. If no authentication is made, the second server host in the list will be queried, and so on. The built-in server
group can only have hosts that are running the specified protocol. For example, the TACACS server group can only have
TACACS server hosts.
The administrator for the switch may set up 5 different authentication techniques per user-defined method list (TACACS /
XTACACS / TACACS+ / local / none) for authentication. These techniques will be listed in an order preferable, and defined by
the user for normal user authentication on the switch, and may contain up to eight authentication techniques. When a user
attempts to access the switch, the switch will select the first technique listed for authentication. If the first technique goes
through its server hosts and no authentication is returned, the switch will then go to the next technique listed in the server group
for authentication, until the authentication has been verified or denied, or the list is exhausted.
Please note that user granted access to the switch will be granted normal user privileges on the switch. To gain acess to admin
level priveledges, the user must enter the
enable admin
command and then enter a password, which was previously
configured by the administrator of the switch.
The TACACS (Terminal Access Controller Access Control System) commands in the Command Line Interface (CLI) are listed
(along with the appropriate parameters) in the following table.
NOTE: TACACS, XTACACS and TACACS+ are separate entities and are not
compatible. The switch and the server must be configured exactly the same, using
the same protocol. (For example, if the switch is set up for TACACS authentication,
so must be the host server.)