xStack DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual
126
Access Authentication Control
The TACACS/XTACACS//RADIUS commands let you secure access to the Switch using the
TACACS/XTACACS//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//RADIUS authentication is enabled on the
Switch, it will contact a TACACS/XTACACS//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.
•
(Terminal Access Controller Access Control System plus
) - Provides detailed access control for
authentication for network devices. is facilitated through Authentication commands via one or more
centralized servers. The protocol encrypts all traffic between the Switch and the daemon, using
the TCP protocol to ensure reliable delivery
In order for the TACACS/XTACACS//RADIUS security function to work properly, a
TACACS/XTACACS//RADIUS server must be configured on a device other than the Switch, called an Authentication
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//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
Authentication Server Groups
, one for each of the TACACS, XTACACS, and RADIUS
protocols. These built-in Authentication Server Groups are used to authenticate users trying to access the Switch. The users will
set
Authentication Server Hosts
in a preferable order in the built-in Authentication Server Groups and when a user tries to gain
access to the Switch, the Switch will ask the first Authentication Server Hosts for authentication. If no authentication is made, the
second server host in the list will be queried, and so on. The built-in Authentication Server Groups can only have hosts that are
running the specified protocol. For example, the TACACS Authentication Server Groups can only have TACACS Authentication
Server Hosts.
The administrator for the Switch may set up six different authentication techniques per user-defined method list
(TACACS/XTACACS//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 Authentication 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 users granted access to the Switch will be granted normal user privileges on the Switch. To gain access to
administrator level privileges, the user must access the
Enable Admin
window and then enter a password, which was previously
configured by the administrator of the Switch.
NOTE:
TACACS, XTACACS and 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.)
