RADIUS vs. TACACS+: What’s the Difference?

Last updated on February 18, 2025

TACACS+ and RADIUS are two common AAA (Authentication, Authorization, and Accounting) protocols. Learning about the differences between these two protocols can help you choose the protocol that best suits your needs. Read on to get to know more differences between RADIUS vs. TACACS+.

TACACS+ vs. RADIUS: What’s the Difference?

The main difference between RADIUS and TACACS+ is that RADIUS is mainly a network access protocol for user authentication, whereas TACACS+ is predominantly used for administrating network devices like routers and switches.

But there are many more differences than just that.

Here’s a handy table that outlines the most important differences between TACACS+ and RADIUS.

TACACS+ vs. RADIUS: Differences Table

RADIUS	TACACS+
RADIUS stands for Remote Authentication Dial-In User Service.	TACACS+ is an abbreviation of Terminal Access Controller Access-Control System Plus.
Documented in RFC 2865.	Described in RFC 1492.
RADIUS uses User Datagram Protocol (UDP) as Transport Layer Protocol.	TACACS+ uses Transmission Control Protocol (TCP) as Transport Layer Protocol.
RADIUS uses UDP port 1812 or 1645 for authentication and port 1813 or 1646 for accounting.	TACACS uses TCP port 49 to communicate between the client and server.
RADIUS provides no support for the external authorization of commands.	TACACS+ provides control over the authorization of commands, allowing granular control.
RADIUS encrypts passwords only, leaving other information unencrypted.	TACACS+ encrypts all packets.
RADIUS bundles authentication and authorization, making it impossible to perform them separately. Accounting can be used separately.	TACACS+ separates Authentication, Authorization, and Accounting, making it possible to use different protocols for authentication and authorization or accounting.
RADIUS does not support command accounting.	TACACS+ supports command accounting.
RADIUS is an open-standard protocol that works with virtually all modern devices.	TACACS+ is Cisco’s proprietary protocol and works with Cisco devices only.
RADIUS supports only one privilege level (limited to privilege mode)	TACACS+ supports multiple privilege levels.
RADIUS supports 802.1x. port-based network access control	TACACS+ does not support 802.1x port-based network access control.
RADIUS is mainly a network access protocol.	TACACS+ is mainly used for device administration using Access Control Server (ACS) servers.
RADIUS has no multiprotocol support – IP only.	TACACS+ has multiprotocol support (IP, Novell, NetBIOS, Apple, X.25).
RADIUS cannot authenticate network devices.	TACACS+ can authenticate network devices.

Advantages of TACACS+ over RADIUS

Here are the reasons why TACACS+ can be a better choice than RADIUS.

• TACACS+ encrypts all packets ensuring higher security than RADIUS, which only encrypts passwords.
• TACACS+ provides control over the authorization of commands, which allows granular control of authorization.
• TACACS+ allows you to use different protocols for authentication and authorization, which improves flexibility.
• TACACS+ supports command accounting and multiple privilege levels.

Advantages of RADIUS over TACACS+

Here’s why RADIUS can be better than the TACACS+ protocol.

• RADIUS works with virtually all routers and switches, while TACACS+ only works with Cisco devices.
• RADIUS supports 802.1x. port-based network access control, while TACACS+ does not.
• RADIUS is better for accounting purposes.

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