Supported Topologies - Cisco Catalyst 2950 Software Configuration Manual

Chapter 8 Configuring 802.1X Port-Based Authentication
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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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In a point-to-point configuration (see
802.1X-enabled switch port. The switch detects the client when the port link state changes to the up state.
If a client leaves or is replaced with another client, the switch changes the port link state to down, and
the port returns to the unauthorized state.
Figure 8-3
as a multiple-host port that becomes authorized as soon as one client is authenticated. When the port is
authorized, all other hosts indirectly attached to the port are granted access to the network. If the port
becomes unauthorized (re-authentication fails or an EAPOL-logoff message is received), the switch
denies access to the network to all of the attached clients. In this topology, the wireless access point is
responsible for authenticating the clients attached to it, and the wireless access point acts as a client to
the switch.
Figure 8-3
Wireless client
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auto—enables 802.1X 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
shows 802.1X-port based authentication in a wireless LAN. The 802.1X port is configured
Wireless LAN Example
Access point
Understanding 802.1X Port-Based Authentication
Figure 8-1 on page 8-2), only one client can be connected to the
Catalyst 2950 switch
Catalyst 2950 Desktop Switch Software Configuration Guide
Authentication
server
(RADIUS)
8-5