A Complete Guide to FreeRADIUS: Features, Installation, and Configuration

Table of Contents

1. What is FreeRADIUS?
2. Why Use FreeRADIUS?
3. Key Features of FreeRADIUS
4. System Requirements
5. How to Install FreeRADIUS
6. Basic Configuration Guide
7. Common Use Cases
8. Security Considerations
9. FreeRADIUS vs Other RADIUS Servers
10. Summary

What is FreeRADIUS?

FreeRADIUS is a free and open-source implementation of the RADIUS protocol (Remote Authentication Dial-In User Service). It is widely used for managing network authentication, authorization, and accounting (AAA). FreeRADIUS is trusted by enterprises, ISPs, universities, and telecom operators worldwide to authenticate millions of users daily.

Why Use FreeRADIUS?

FreeRADIUS offers a powerful, scalable, and highly customizable AAA solution. It is the most popular RADIUS server globally due to:

• Flexibility: Supports various backends like MySQL, PostgreSQL, LDAP, etc.
• Performance: Can handle thousands of requests per second.
• Community Support: Backed by a strong open-source community and comprehensive documentation.

Key Features of FreeRADIUS

• ✅ Supports EAP (Extensible Authentication Protocol)
• ✅ Full IPv6 compatibility
• ✅ Integration with LDAP, SQL, and Active Directory
• ✅ Dynamic client configuration
• ✅ Detailed logging and auditing
• ✅ Supports virtual servers
• ✅ Load balancing and failover capabilities

System Requirements

Minimum requirements for FreeRADIUS server:

Resource	Requirement
OS	Linux (Ubuntu/Debian/CentOS), macOS
RAM	512 MB (minimum)
Disk Space	100 MB (excluding log files)
Dependencies	libssl, libpcap, libtalloc

How to Install FreeRADIUS

🔧 On Ubuntu / Debian:

sudo apt update
sudo apt install freeradius freeradius-utils -y

🔧 On CentOS / RHEL:

sudo dnf install freeradius freeradius-utils -y

📁 Directory Structure:

• /etc/freeradius/3.0/: Main configuration directory
• /etc/freeradius/3.0/mods-enabled/: Enabled modules
• /etc/freeradius/3.0/sites-enabled/: Virtual server configs

Basic Configuration Guide

1. Add a Client (e.g., Wireless AP)

Edit: /etc/freeradius/3.0/clients.conf

client wifi-ap {
    ipaddr = 192.168.1.1
    secret = yoursharedsecret
}

2. Configure Users

Edit: /etc/freeradius/3.0/mods-config/files/authorize

alice Cleartext-Password := "mypassword"
bob   Cleartext-Password := "anotherpass"

3. Test Authentication

radtest alice mypassword localhost 0 yoursharedsecret

Expected output should contain Access-Accept.

Common Use Cases

• 🔐 Wi-Fi Authentication (802.1X)
• 🏢 Enterprise VPN Authentication
• 📶 ISP Dial-up or DSL User Management
• 🎓 Campus Network Access
• 📈 Accounting and Session Tracking

Security Considerations

• Always use strong shared secrets
• Restrict access to port 1812 (authentication) and 1813 (accounting)
• Use EAP-TLS for secure wireless authentication
• Enable TLS/SSL if using RADIUS over Internet
• Monitor logs in /var/log/freeradius/radius.log

FreeRADIUS vs Other RADIUS Servers

Feature	FreeRADIUS	Microsoft NPS	Cisco ISE
Open Source	✅ Yes	❌ No	❌ No
Customizable	✅ High	❌ Limited	⚠️ Medium
Price	Free	Requires License	Very Expensive
Performance	Excellent	Good	Excellent

Summary

FreeRADIUS is a powerful and enterprise-ready solution for managing authentication and network access control. Its open-source nature allows for deep customization, while still being scalable for large environments.

Whether you’re running a Wi-Fi network in a small office, handling thousands of users in a university, or managing broadband users in an ISP, FreeRADIUS is an excellent choice.

❓ Frequently Asked Questions (FAQ) About FreeRADIUS

1. What is FreeRADIUS?

FreeRADIUS is an open-source implementation of the RADIUS protocol used to manage network authentication, authorization, and accounting (AAA). It’s widely deployed in enterprises, ISPs, universities, and telecom environments due to its flexibility and performance.

2. How does FreeRADIUS differ from other RADIUS servers?

FreeRADIUS stands out because it’s free, highly customizable, and supports a broad range of authentication methods and back-ends (like LDAP and SQL). Many commercial RADIUS servers lack this level of flexibility and cost money.

3. What platforms does FreeRADIUS support?

FreeRADIUS runs on most Unix-like systems, including popular Linux distributions such as Ubuntu, Debian, and CentOS. It does not natively run on Windows without compatibility layers.

4. Do I need special hardware to run FreeRADIUS?

No — FreeRADIUS is lightweight. Simple deployments can run with minimal RAM and disk space. For large environments handling millions of authentications, plan your infrastructure accordingly.

5. Can I use FreeRADIUS with databases like MySQL or PostgreSQL?

Yes — FreeRADIUS supports multiple back-ends such as MySQL, PostgreSQL, LDAP, and Active Directory. You can configure it to read user credentials and accounting data directly from these databases.

6. How do I test if my FreeRADIUS installation is working?

After installation, use the radtest utility to send a test authentication request. An Access-Accept response indicates the server is running properly.

7. What are common use cases for FreeRADIUS?

Typical scenarios include Wi-Fi authentication (802.1X), enterprise VPN authentication, ISP user management, and campus network access control, as well as accounting and session tracking.

8. How can I increase security on my FreeRADIUS server?

Use strong shared secrets, restrict access to RADIUS ports (1812/1813), enable EAP-TLS for certificate-based authentication, and monitor logs regularly for suspicious activity.

9. Where can I find official FreeRADIUS documentation and support?

Comprehensive documentation, including FAQs, module guides, and configuration examples, is available on the FreeRADIUS official site. The community wiki and mailing lists are also helpful resources.

10. What should I do if FreeRADIUS doesn’t start after installation?

Run the server in debugging mode (radiusd -X) to view detailed errors, check your configuration files for syntax issues, and verify that required modules (like SQL or LDAP) have their dependencies installed.