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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 9      Configuring IEEE 802.1x Port-Based Authentication
    Configuring IEEE 802.1x Authentication
Configuring IEEE 802.1x Authentication
To configure IEEE 802.1x port-based authentication, you must enable AAA and specify the 
authentication method list. A method list describes the sequence and authentication methods to be 
queried to authenticate a user. 
The software uses the first method listed to authenticate users. If that method fails to respond, the 
software selects the next authentication method in the method list. This process continues until there is 
successful communication with a listed authentication method or until all defined methods are 
exhausted. If authentication fails at any point in this cycle, the authentication process stops, and no other 
authentication methods are attempted.
To allow VLAN assignment, you must enable AAA authorization to configure the switch for all 
network-related service requests.
This is the IEEE 802.1x authentication, authorization and accounting process:
Step 1 A user connects to a port on the switch.
Step 2 Authentication is performed.
Step 3 VLAN assignment is enabled, as appropriate, based on the RADIUS server configuration.
Step 4 The switch sends a start message to an accounting server.
Step 5 Re-authentication is performed, as necessary.
Step 6 The switch sends an interim accounting update to the accounting server that is based on the result of 
re-authentication.
Step 7 The user disconnects from the port.
Step 8 The switch sends a stop message to the accounting server.
Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x port-based 
authentication:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
aaa new-model Enable AAA.
Step 3
aaa authentication dot1x {default} 
method1 [method2...]
Create an IEEE 802.1x authentication method list.
To create a default list that is used when a named list is not specified in 
the authentication command, use the default keyword followed by the 
methods that are to be used in default situations. The default method list 
is automatically applied to all ports.
Enter at least one of these keywords:
• group radius—Use the list of all RADIUS servers for authentication. 
• none—Use no authentication. The client is automatically 
authenticated by the switch without using the information supplied by 
the client.
Step 4
dot1x system-auth-control Enable IEEE 802.1x authentication globally on the switch.