Access Authentication Control - D-Link DES-3528 User Manual

xStack DES-3528 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual

Access Authentication Control

The TACACS/XTACACS/TACACS+/RADIUS commands allow users to 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
In order for the
TACACS/XTACACS/TACACS+/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/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 Authentication Server Groups, one for each of the TACACS, XTACACS, TACACS+ 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/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 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 when the user logins to the device successfully through
none method, the "user" priviledge level is the only level assigned. If the user wants to get the administration privilege
level, the user must use the "enable admin" command to promote his privilege level. However when the user logins to
the device successfully through the RADIUS server or through the local method, 3 kinds of privilege levels can be
assigned to the user and the user can not use the "enable admin" command to promote to the admin privilege level.
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.)
TACACS/XTACACS/TACACS+/RADIUS security
TACACS/XTACACS/TACACS+server or
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function to work properly, a