Configure TACACS+

Use the TACACS+ Settings page to manage Terminal Access Controller Access Control System (TACACS+) authentication.

About TACACS+ Management

Terminal Access Controller Access Control System (TACACS)+ is an authentication and accounting protocol designed for use with UNIX platforms. TACACS+ divides authentication, authorization, and accounting into separate functions. A remote TACACS+ server stores the store user and password information. This information is supplied during the authentication process. TCP is used as the communications protocol for TACACS+ messages.

TACACS+ authentication support is provided for the following management interfaces on EdgeMarc:

• HTTP/HTTPS
• Console Login
• SSH
• Telnet

If TACACS+ is enabled, the system prompts for a username and password whenever a user attempts to log in. Upon receiving the username and password, the EdgeMarc attempts to connect with the TACACS+ server. When the connection is established, the user authentication request is transmitted to the TACACS+ server. The details of the request depend upon the authentication mode configured in the EdgeMarc.

TACACS+ authentication may result in any of the following scenarios:

• The TACACS server authenticates the user, and login is successful.
• Connection to the TACACS+ server fails (times out). Administrator password authentication is used for the next login attempt.
• Connection is established with the TACACS+ server, but the authentication parameters (username and password) are not validated, and authentication fails. TACACS+ authentication mechanism is used again for the next login attempt.

TACACS+ Authentication

The EdgeMarc supports the following TACACS+ authentication modes:

• ASCII—The username is sent as part of the TACACS client request, and the password is sent as part of the continue message.
• Password Authentication Protocol (PAP)—Both username and password are sent as part of the request message.
• Challenge Handshake Authentication Protocol (CHAP)—The password calculates the response to a random challenge. Both the challenge and response are sent as part of the TACACS+ request message.

For successful authentication, the username and password entered for TACACS+ authentication at run-time must match the values configured on the TACACS+ server. The username and password settings depend on the authentication mode (PAP/CHAP/ASCII).

GUI Interaction Logging

When TACACS+ logging is enabled, all the configured parameters that have changed from their original stored values are sent as a sequence of attribute-value pairs (AV pairs). The format is attributename=attributevalue, where the attributename is the name of the configurable parameter (similar to the GUI field name), and the attributevalue is the new value of that parameter.

All TACACS+ parameters except for TACACS+ Authentication Mode apply to both logging and authentication features.

For the GUI interface, the TACACS+ logging message also contains the following protocol-specific fields:

• service=http
• page_name=symbolic name of the web page e.g. pg_vpn
• operation=self explanatory action name such as submit, add, delete

For Telnet, SSH, and console, the logging messages consist of the following: Command=issued command.

If the parameter value or command name exceeds the maximum AV Pair length of 255 characters, then the message is broken into multiple AV pairs as follows (this is a TACACS+ limitation):

• attrname=attrvalue
• attrname_continued=attrvalue_cont.

In addition to the field information, the TACACS+ logging message also contains some protocol-specific fields.

TACACS+ and RADIUS

The EdgeMarc supports TACACS+ or Remote Authentication Dial In User Service (RADIUS), but not both simultaneously. If you attempt to enable TACACS+ while RADIUS is enabled, or vice versa, an error message is displayed, and the configuration is not applied.

If TACACS+ or RADIUS is enabled, but the system cannot communicate with the server (TACACS+ or RADIUS, respectively), the system reverts to administrator password authentication.

Using the TACACS+ Configuration Page

This section outlines how to use the TACACS+ configuration page.

Before you Begin

1. Disable RADIUS on your system:
   1. Choose Admin > RADIUS Settings.
   2. Clear the Enable RADIUS checkbox.

   3. Click Submit.

      Note

      Refer to Configure RADIUS Settings for more information about managing RADIUS settings.

2. By default, TACACS performs authentication on every page access. To prevent this, enable Session Management on the Session/User Management - Advanced page:
   1. Choose Users > Advanced or click the Session Management Configuration link provided on the TACACS+ Settings page and click Advanced.
   2. Select the Enable Session Management checkbox.
   3. Click Submit.
      Refer to Configure Session/User Management.

Configuring TACACS+ Settings

From the TACACS+ Settings page, you can configure a single TACACS+ server or a redundant TACACS+ server for the system.

To Configure TACACS+ Settings

1. Choose Admin > TACACS Settings.
   

2. Configure settings using the information in the following table as a guide.

   TACACS Settings

   Item	Description
   Enable TACACS+ Authentication	Select the Enable TACACS+ Authentication checkbox.
   Enable TACACS+ Logging	If enabled, all configuration changes over HTTP, HTTPS, SSH, Telnet, and System Console are logged. Note: Enable TACACS+ Authentication and Enable TACACS+ Logging can be independently enabled.
   TACACS+ Server Address	Enter the TACACS+ server IP address to contact for authentication.
   Shared Secret	Displays whether a password for TACACS+ authentication requests has been set.
   Edit Secret	Select the Edit Secret checkbox to set the shared secret password.
   Shared Secret	Enter a password for the TACACS+ request. The client and the server must have the same secret.
   Shared Secret (confirm)	Reenter the shared secret to confirm.
   Server Timeout (in seconds)	Enter the time in seconds that a TACACS+ server does not respond to a request and is deemed unavailable. The valid range is 1 to 100 seconds; the default is 5 seconds.
   TACACS+ Authentication Mode	Select a TACACS+ authentication mode from the drop-down list: •ASCII—The username is sent as part of the TACACS client request, and the password is sent as part of the continue message. •Password Authentication Protocol (PAP)— Both username and password are sent as part of the request message. •Challenge Handshake Authentication Protocol (CHAP)—The password calculates the response to a random challenge. Both the challenge and response are sent as part of the TACACS+ request message.
   Enable TACACS+ Logging	Select the Enable TACACS+ Logging checkbox to enable logging for all configuration changes over HTTP, HTTPS, SSH, Telnet, and the system console.
   TACACS+ Server	Click the Create button to configure a redundant TACACS+ server. For information, see procedure To configure a redundant TACACS+ server configuration.

3. Click Submit to make your changes take effect. A message indicates that service will be temporarily interrupted.

4. Click OK to confirm.

To Configure a Redundant TACACS+ Server Settings 

A redundant TACACS+ server configuration enhances the reliability and availability of network authentication and adds failover capabilities. This configuration provides the following capabilities:

• Primary-Secondary Server Configuration: The system is configured to communicate with either the primary or secondary TACACS+ server.

• Failover Mechanism: Upon detecting the failure of the primary server, the system seamlessly switches authentication control to the secondary server.

• Automatic Recovery: When the primary server becomes available again, control reverts to it automatically, ensuring optimal resource utilization.

• Fallback to Root User: If both primary and secondary servers fail, authentication control falls back to the root user.

Use the following procedure to configure a redundant TACACS+ server.

1. Choose Admin > TACACS Settings.
2. Click the Create button to add a TACACS+ Server.
   
   
   The List of TACACS Server table displays.  
3. Configure settings using the information in the Add a TACACS+ Server frame.
   

   Item	Description
   Server IP	Type the server IP address. The IP address of the TACACS+ server is used when attempting to authenticate via TACACS+. There is no default for the Server IP Address.
   Server Key	Type the server key. Key length: Up to 120 characters This value is used for authentication of the TACACS+ request. The client and the server must have the same secret. There is no default for the Server Key.
   Confirm Key	Type the server key again. The server key verifies that the entered secret key matches the expected value. This confirmation step is crucial for preventing configuration errors and ensuring the security of authentication processes.

4. Click Add. The TSCACS server appears under the List of TACACS Server frame. Note that you can only add two TACACS servers. 
   
   
   
   Note

   The List of TACACS Server table not only provides a comprehensive list of configured TACACS servers within the network infrastructure but also information about network authentication and authorization processes.

   
   
5. Click Submit to save your configuration changes to theEdgeMarc,

Disabling TACACS+ Services

This section outlines how to disable the TACACS+ services.

To Disable the TACACS+ Services

1. To disable TACACS+ authentication, clear the Enable TACACS+ Authentication checkbox and click Submit. 

   Note that clicking Submit only disables the TACACS process and does not impact network operations.
2. To disable TACACS+ logging, clear the Enable TACACS+ Logging checkbox and click Submit.