Port-Based Authentication And Switch Stacks - Cisco Catalyst 2960-X Security Configuration Manual
Cisco ios release 15.0(2)ex
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- Command reference manual (135 pages) ,
- Hardware installation manual (34 pages) ,
- Getting started manual (25 pages)
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Configuring IEEE 802.1x Port-Based Authentication
When a client is successfully authenticated, the port changes to the authorized state, allowing all traffic for
the client to flow normally. If the port is configured as a voice VLAN port, the port allows VoIP traffic and
802.1x protocol packets before the client is successfully authenticated.
CDP bypass is not supported and may cause a port to go into err-disabled state.
Note
If a client that does not support 802.1x authentication connects 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 standard, 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 authentication port-control interface configuration
command and these keywords:
• force-authorized—disables 802.1x authentication and causes the port to change to the authorized state
• force-unauthorized—causes the port to remain in the unauthorized state, ignoring all attempts by the
• auto—enables 802.1x authentication and causes the port to begin in the unauthorized state, allowing
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 resend 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 change to the unauthorized
state.
If the link state of a port changes from up to down, or if an EAPOL-logoff frame is received, the port returns
to the unauthorized state.
Port-Based Authentication and Switch Stacks
If a switch is added to or removed from a switch stack, 802.1x authentication is not affected as long as the IP
connectivity between the RADIUS server and the stack remains intact. This statement also applies if the stack
master is removed from the switch stack. Note that if the stack master fails, a stack member becomes the new
stack master by using the election process, and the 802.1x authentication process continues as usual.
If IP connectivity to the RADIUS server is interrupted because the switch that was connected to the server is
removed or fails, these events occur:
OL-29048-01
without any authentication exchange required. The port sends and receives normal traffic without
802.1x-based authentication of the client. This is the default setting.
client to authenticate. The switch cannot provide authentication services to the client through the port.
only EAPOL frames to be sent and received through the port. The authentication process begins when
the link state of the port changes 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 MAC address.
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
Port-Based Authentication and Switch Stacks
271
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