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Configuring RADIUS
RADIUS is a protocol for implementing Authentication, Authorization, and Accounting (AAA). For more
information about AAA, see "Configuring AAA."
Overview
Remote Authentication Dial-In User Service (RADIUS) is a distributed information interaction protocol that
uses a client/server model. It can protect networks against unauthorized access and is often used in
network environments with requirements for both high security and remote user access.
RADIUS uses UDP as the transport protocol. It uses UDP port 1812 for authentication and UDP port 1813
for accounting.
RADIUS was originally designed for dial-in user access. With the addition of new access methods,
RADIUS has been extended to support additional access methods, such as Ethernet and ADSL. RADIUS
provides access authentication and authorization services, and its accounting function collects and
records network resource usage information.
Client/Server model
The RADIUS client runs on the NASs located throughout the network. It passes user information to
RADIUS servers and acts on the responses to, for example, reject or accept user access requests.
The RADIUS server runs on the computer or workstation at the network center and maintains information
related to user authentication and network service access. It listens to connection requests, authenticates
users, and returns user access control information (for example, rejecting or accepting the user access
request) to the clients.
In general, the RADIUS server maintains the following databases: Users, Clients, and Dictionary.
Figure 413 RADIUS server databases
• Users—Stores user information, such as the usernames, passwords, applied protocols, and IP
addresses.
• Clients—Stores information about RADIUS clients, such as shared keys and IP addresses.
• Dictionary—Stores RADIUS protocol attributes and their values.
RADIUS servers
Users Clients Dictionary
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