Ports In Authorized And Unauthorized States; Supported Topologies - Cisco 6500 Series Software Configuration Manual

Understanding 802.1X Port-Based Authentication

Ports in Authorized and Unauthorized States

The switch port state determines whether or not the client is granted access to the network. The port
starts in the unauthorized state. While in this state, the port disallows all ingress and egress traffic except
for 802.1X protocol packets. When a client is successfully authenticated, the port transitions to the
authorized state, allowing all traffic for the client to flow normally.
If a client that does not support 802.1X is connected to an unauthorized 802.1X port, the switch requests
the client's identity. In this situation, the client does not respond to the request, the port remains in the
unauthorized state, and the client is not granted access to the network.
In contrast, when an 802.1X-enabled client connects to a port that is not running the 802.1X protocol,
the client initiates the authentication process by sending the EAPOL-start frame. When no response is
received, the client sends the request for a fixed number of times. Because no response is received, the
client begins sending frames as if the port is in the authorized state.
You control the port authorization state by using the dot1x port-control interface configuration
command and these keywords:
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If the client is successfully authenticated (receives an Accept frame from the authentication server), the
port state changes to authorized, and all frames from the authenticated client are allowed through the
port. If the authentication fails, the port remains in the unauthorized state, but authentication can be
retried. If the authentication server cannot be reached, the switch can retransmit the request. If no
response is received from the server after the specified number of attempts, authentication fails, and
network access is not granted.
When a client logs off, it sends an EAPOL-logoff message, causing the switch port to transition to the
unauthorized state.
If the link state of a port transitions from up to down, or if an EAPOL-logoff frame is received, the port
returns to the unauthorized state.

Supported Topologies

The 802.1X port-based authentication is supported in two topologies:
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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
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force-authorized—Disables 802.1X port-based authentication and causes the port to transition to
the authorized state without any authentication exchange required. The port transmits and receives
normal traffic without 802.1X-based authentication of the client. This is the default setting.
force-unauthorized—Causes the port to remain in the unauthorized state, ignoring all attempts by
the client to authenticate. The switch cannot provide authentication services to the client through the
interface.
auto—Enables 802.1X port-based authentication and causes the port to begin in the unauthorized
state, allowing only EAPOL frames to be sent and received through the port. The authentication
process begins when the link state of the port transitions from down to up or when an EAPOL-start
frame is received. The switch requests the identity of the client and begins relaying authentication
messages between the client and the authentication server. Each client attempting to access the
network is uniquely identified by the switch by using the client's MAC address.
Point-to-point
Wireless LAN
Chapter 25 Configuring IEEE 802.1X Port-Based Authentication
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