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Command tacacs-server directed-request on Cisco IOS Routers

Created by Deepak Sharma in Articles 29 Aug 2024
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The TACACS-server directed-request command is a critical feature in Cisco security that enhances the authentication process for network devices. This command enables the configuration of a TACACS+ server to direct specific authentication requests to designated servers, improving security management and control over user access.

By utilizing this command, network administrators can streamline authentication processes, ensuring that only authorized users gain access to sensitive resources while maintaining a robust security posture within the network infrastructure.

In this article, we are going to understand about TACACS-server directed-request command in simple language. Understanding this command is very important as it is a fundamental concept in every Cisco security training course.

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What is TACACS?

TACACS full form is Terminal Access Controller Access-Control System which is a network authentication protocol that is used to provide centralized authentication, authorization, and accounting (AAA) services for network devices.

A TACACS server runs the TACACS+ protocol which works on the AAA model i.e. It is used to Authenticate, Authorize, Accounting for all the users who are trying to access network devices such as routers, switches, and firewalls. The Cisco Identity Services Engine (ISE) can act as a TACACS server along with open-source Linux platforms.

In case you are more interested in learning Cisco ISE with an expert instructor in live sessions and how Tacacs is configured on it with many more scenarios. Feel free to contact our learning advisors for more information.

It has a database in which the user's information is stored, when any user tries to access a network device, it verifies the user's credentials (username and password) and grants or denies access to them based on the user's authorization level.

TACACS+ is an enhanced version of TACACS supported by Cisco ISE, that provides more security features like encryption and improved authentication. TACACS+ is widely used in enterprise networks to provide centralized AAA services, enabling administrators to manage and monitor access to network devices from a single location.

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Configure TACACS Servers on the Cisco Router

Now let's have a look and understand how the command “tacacs-server directed-request” behaves. Suppose we have two Tacacs servers configured on a Cisco router (there may be more in the configuration order list).

tacacs-server host 10.0.0.1

tacacs-server host 172.16.0.1

The router will use the IP address which is first appearing in the configuration. In this case, it will use 10.0.0.1, and then the router will create a session with tacacs server and the user will be authenticated.

If the first tacacs IP is not reachable then the router will use the next tacacs IP in the configuration order list for authentication.

The use case of the command “tacacs-server directed-request” is that it allows a user to specify a particular tacacs IP address for authentication instead of using the first tacacs IP address that appeared in the configuration order list.

It also applies to Authorization and Accounting as well along with Authentication.

Configure "tacacs-server directed-request" Command

Now suppose we also have “tacacs-server directed-request” command with two tacacs servers configured, one is used as the company’s tacacs Server, and the other is managed by its service provider.

tacacs-server directed-request

tacacs-server host 10.0.0.1

tacacs-server host 172.16.0.1

Login Using Service Provider TACACS

In this case, company users will be able to log in as usual, but the service provider needs to contact the device as:

[Service_Provider_Machine]$ telnet router_ip

Username: xyz@172.16.0.1    //xyz is the username for authentication with tacacs ip 172.16.0.1

Password:

Router>

Conclusion

In conclusion, understanding the tacacs-server directed-request command is an essential skill in every network security training on Cisco environments. This command allows administrators to direct authentication requests to specific TACACS+ servers, improving access control and management.

By effectively implementing this command, organizations can ensure that user authentication is streamlined and secure, reinforcing their overall security posture while managing network access efficiently.

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Deepak Sharma

He is a senior solution network architect and currently working with one of the largest financial company. He has an impressive academic and training background. He has completed his B.Tech and MBA, which makes him both technically and managerial proficient. He has also completed more than 450 online and offline training courses, both in India and ...

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FAQ

A TACACS (Terminal Access Controller Access-Control System) server is a centralized authentication, authorization, and accounting (AAA) system that controls access to network devices. It verifies user credentials and determines their permissions. What
TACACS+ is an enhanced version of TACACS that provides better security through encryption and supports multiple protocols like PPP, SLIP, and ARA. TACACS only supports ASCII logins.
To access a TACACS server, configure your network devices with the server's IP address and shared secret key. Users can then authenticate through the TACACS server to gain access to the devices.
TACACS supports three types of authentication: ASCII (plain text passwords), PAP (Password Authentication Protocol), and CHAP (Challenge-Handshake Authentication Protocol). The choice depends on the security requirements and supported protocols of the network devices.

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