RADIUS Protocol: A Comprehensive Guide

RADIUS Protocol: A Comprehensive Guide

Understanding RADIUS Protocol: A Comprehensive Guide

In today’s digital age, security is a top priority for businesses and organizations. One of the most widely used security protocols in the world is RADIUS, which stands for Remote Authentication Dial-In User Service. RADIUS is used to authenticate and authorize access to network resources, including servers, routers, and wireless access points.

In this comprehensive guide, we will take an in-depth look at the RADIUS protocol, how it works, and its benefits. By the end of this article, you will have a better understanding of the RADIUS protocol and how it can benefit your organization.

What is RADIUS?

RADIUS is a networking protocol that provides centralized authentication, authorization, and accounting (AAA) for users who connect to and use a network service. It was originally developed by Livingston Enterprises for use with dial-up networks, but it has since become a widely adopted standard for all types of networks.

RADIUS is used by network administrators to manage access to network resources. When a user attempts to connect to a network, the RADIUS server is contacted to verify the user’s credentials. If the credentials are valid, the RADIUS server sends an access approval message to the network access server, which grants access to the user.

How RADIUS Works?

RADIUS works by authenticating users who are trying to access a network resource. It does this by using a username and password, which are passed to the RADIUS server for validation. The RADIUS server then sends a response back to the network access server, which either grants or denies access.

RADIUS also provides authorization and accounting services. Authorization involves determining which resources a user is allowed to access, based on their user profile. Accounting involves tracking the resources that a user has accessed, including the amount of time they have spent on the network and the amount of data they have transmitted.

RADIUS Authentication Methods

RADIUS supports a variety of authentication methods, including:

  • Password-based authentication: This is the most common method of authentication, where users enter a username and password to gain access to the network.
  • Certificate-based authentication: This method uses digital certificates to authenticate users.
  • Token-based authentication: Token-based authentication uses a physical device, such as a smart card or security token, to authenticate users.

Benefits of Using RADIUS

Improved Security

RADIUS provides strong authentication and authorization services, which helps to ensure that only authorized users can access network resources. This helps to prevent unauthorized access and reduce the risk of data breaches.

Centralized Management

RADIUS allows for centralized management of user accounts, which makes it easier to manage access to network resources. This can save time and reduce the risk of errors.


RADIUS is highly scalable, which means it can be used to manage access to networks of any size. This makes it an ideal solution for both small and large organizations.


RADIUS is a widely adopted standard, which means it is compatible with a wide range of networking equipment, including servers, routers, and wireless access points.

Note: The diagram above shows a high-level overview of how RADIUS works, with the user (A) requesting access to the network through the RADIUS client (B). The RADIUS server (C) then authenticates and authorizes the request (D), granting access (E) or denying access (F). Finally, the RADIUS server records accounting information (G) to track network usage (H).

Diagram with high-level overview of how RADIUS works


What Integrations are allowed with RCDevs' Radius Bridge?
RADIUS Bridge provides the RADIUS interface on top of the OpenOTP server. And it is included in your OpenOTP license at no extra charge. The RADIUS standard is supported by all major security products on the market. You can also implement OpenOTP authentication methods for
  • VPN Servers (Checkpoint, Cisco ISE/ASA, F5, Fortigate, Palo Alto…)
  • Microsoft VPN, TMG, UAG
  • Citrix (Access Gateway, XenApp, Netscaler)
  • VMWare View
  • NAC Enterprise Wifi (EAP-TLS/GTC, TTLS)
  • Radius-enabled Linux services (OpenVPN, Apache…)
  • SWIFT Alliance Access
  • More info
    What types of non-RADIUS applications can be integrated with RADIUS Bridge?
    RADIUS Bridge supports various types of non-RADIUS applications, including web applications, VPNs, firewalls, and network devices. You can configure RADIUS Bridge to communicate with these applications using standard protocols such as LDAP, RDP, SSH, and TACACS+.
    Can RADIUS Bridge be used for high availability and load balancing?
    Yes, RADIUS Bridge supports high availability and load balancing configurations. You can set up multiple RADIUS Bridge instances to work together in a cluster, with each instance sharing the load and providing redundancy in case of failure.
    What authentication protocols does RCDevs' Radius Bridge support?
    Radius Bridge supports a wide range of authentication protocols, including RADIUS, SAML, LDAP, Active Directory, OAuth, and OpenID Connect. It also supports a variety of multi-factor authentication methods, such as SMS, email, and push notifications.
    OpenOTP and WebADM support a range of RADIUS protocols through the OpenOTP Radius Bridge, which provides the RADIUS RFC-2865 (Remote Authentication Dial-In User Service) API for the OpenOTP Authentication Server. This setup allows for a variety of configurations, including handling of passwords and concatenation, support for Active Directory User Principal Names (UPNs), and the ability to pass additional information such as client ID and user source IP address through specific RADIUS attributes​​. The OpenOTP Radius Bridge is compatible with numerous integrations and authentications, including but not limited to Palo Alto, NetIQ, pfSense, Swift Alliance Access, OpenVPN, EAP Authentications, and Microsoft Network Policy Server, among others. This extensive support underscores the flexibility and adaptability of the OpenOTP and WebADM platforms to various network and security requirements.
    More info : RCDevs' Radius Bridge
    Can RCDevs' Radius Bridge be deployed on-premise or in the cloud?
    Yes, Radius Bridge can be deployed on-premise or in the cloud, depending on the specific needs and requirements of the organization. RCDevs provides both options to ensure flexibility and scalability. More infos : Radius Bridge documentation
    How can I troubleshoot issues with RADIUS Bridge?
    RADIUS Bridge provides detailed logging and debugging information that can help you diagnose and resolve issues. You can view logs and configuration files from the web interface or access them directly from the server. Additionally, RADIUS Bridge provides a testing tool that allows you to simulate RADIUS authentication and accounting requests to verify that the system is functioning correctly.
    How to secure my VPN endpoint with RCDevs's Radius Bridge?
    RCDevs' RADIUS Bridge integrates seamlessly with your VPN infrastructure, enabling robust multi-factor authentication (MFA) that enhances security across various third-party systems. It supports a wide range of VPN servers and other RADIUS-compliant services, allowing for flexible user authentication options including OTPs, passkeys, and biometrics. The system can handle multiple authentication mechanisms like challenge-response or concatenated password entry, tailored to your network or geographic location. It's designed to function with existing AD servers and requires no additional OpenOTP configuration, ensuring an efficient setup and high-performance operation with support for clustering and high availability. For more details, you can visit their website: RCDevs RADIUS Bridge.