Cisco NM-8B-U - HW ROUTERS L-M User Manual page 11

16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series
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
packets. When a client is successfully authenticated, the port changes 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 802.1x, 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:
• force-authorized—disables 802.1x and causes the port to change 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 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 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's MAC address.
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 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.
Supported Topologies
The 802.1x port-based authentication is supported in two topologies:
Point-to-point
•
Wireless LAN
•
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 1 on page 9), only one client can be connected to the
Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ
Feature Overview
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