Allied Telesis AT-9724TS - Manual (Page 136)

7-3 Access Authentication Control
The TACACS / XTACACS / TACACS+ / RADIUS commands let you 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 security function to work properly, a 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 6 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 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 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.)
Policy & Parameters
This command will enable an administrator-defined authentication policy for users trying to access the Switch.When enabled, the device will check the Login
Method List and choose a technique for user authentication upon login.
To access the following window, click Security Management > Access Authentication Control > Policy & Parameters:
Figure 7- 5. Policy & Parameters Settings window
135 Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch