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DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch CLI Manual
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8
ACCESS AUTHENTICATION CONTROL COMMANDS
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:
a) 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.
b) 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.
c) 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:
1. The server verifies the username and password, and the user is granted normal user privileges on the Switch.
2. The server will not accept the username and password and the user is denied access to the Switch.
3. 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.