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Configuring AAA
Overview
Authentication, Authorization, and Accounting (AAA) provides a uniform framework for implementing
network access management. AAA specifies the following security functions:
• Authentication—Identifies users and verifies their validity.
• Authorization—Grants different users different rights and controls their access to resources and
services. For example, you can use this function to grant a user who has successfully logged in to the
device read and print permissions to the files on the device, and prevent a guest from reading or
printing the files.
• Accounting—Records network usage details of users, including the service type, start time, and
traffic. This function enables time-based and traffic-based charging and user behavior auditing.
Typically, AAA uses a client/server model. The client runs on the access device, or the network access
server (NAS), which authenticates user identities and controls user access. The server maintains user
information centrally. See Figure 1.
Figure 1 AAA network
diagram
A user who wants to access networks or resources beyond the NAS sends its identity information to the
NAS, which transparently passes the user information to the servers. The servers perform user
authentication, authorization, and accounting and return the result to the NAS. Based on the result, the
NAS determines whether to permit or deny the access request.
AAA has various implementations, including RADIUS, HWTACACS, and LDAP. RADIUS is most often
used.
The network in Figure 1 ha
s o
ne RADIUS server and one HWTACACS server. You can use different
servers to implement different security functions. For example, you can use the HWTACACS server for
authentication and authorization, and use the RADIUS server for accounting.
You can choose the security functions provided by AAA as needed. For example, if your company wants
employees to be authenticated before they access specific resources, you would deploy an
authentication server. If network usage information is needed, you would also configure an accounting
server.
Remote user
NAS
RADIUS server
HWTACACS server
Internet
Network
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