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xStack® DES-3200 Series Layer 2 Ethernet Managed Switch CLI Reference Guide
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ACCESS AUTHENTICATION CONTROL COMMANDS
The TACACS / XTACACS / TACACS+ / RADIUS commands allows secure access to the Switch using the TACACS /
XTACACS / TACACS+ / RADIUS protocols. When a user logs in to the Switch or tries to access the administrator level
privilege, he or she is prompted for a password. If TACACS / XTACACS / TACACS+ / RADIUS authentication is enabled on the
Switch, it will contact a TACACS / XTACACS / TACACS+ / RADIUS 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 codes 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.
The Switch also supports the RADIUS protocol for authentication using the Access Authentication Control commands. RADIUS
or Remote Authentication Dial In User Server also uses a remote server for authentication and can be responsible for receiving
user connection requests, authenticating the user and returning all configuration information necessary for the client to deliver
service through the user. RADIUS may be facilitated on this Switch using the commands listed in this section.
In order for the TACACS / XTACACS / TACACS+ / RADIUS security function to work properly, a TACACS / XTACACS /
TACACS+ / RADIUS 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+ / RADIUS server to verify, and the server will
respond with one of three messages:
The server verifies the username and password, and the user is granted normal user privileges on the Switch.
The server will not accept the username and password and the user is denied access to the Switch.
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 four built-in server groups, one for each of the TACACS, XTACACS, TACACS+ and RADIUS 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 access 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 five different authentication techniques per user-defined method list (TACACS /
XTACACS / TACACS+ / RADIUS / 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 access to admin
level privileges, the user must enter the enable admin command and then enter a password, which was previously configured by
the administrator of the Switch.
The Access Authentication Control 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.)