D-Link DGS-3630 Series Reference Manual page 473

DGS-3630 Series Layer 3 Stackable Managed Switch Web UI Reference Guide
The original intent behind the development of 802.1X was to leverage the characteristics of point-to-point in LANs. As
any single LAN segment in such infrastructures has no more than two devices attached to it, one of which is a Bridge
Port. The Bridge Port detects events that indicate the attachment of an active device at the remote end of the link, or
an active device becoming inactive. These events can be used to control the authorization state of the Port and initiate
the process of authenticating the attached device if the Port is unauthorized. This is the Port-based Network Access
Control.
Port-based Network Access Control
Once the connected device has successfully been authenticated, the Port then becomes Authorized, and all
subsequent traffic on the Port is not subject to access control restriction until an event occurs that causes the Port to
become Unauthorized. Hence, if the Port is actually connected to a shared media LAN segment with more than one
attached device, successfully authenticating one of the attached devices effectively provides access to the LAN for all
devices on the shared segment. Clearly, the security offered in this situation is open to attack.
Figure 9-10 Example of Typical Port-based Configuration
Host-based Network Access Control
In order to successfully make use of 802.1X in a shared media LAN segment, it would be necessary to create "logical"
Ports, one for each attached device that required access to the LAN. The Switch would regard the single physical Port
connecting it to the shared media segment as consisting of a number of distinct logical Ports, each logical Port being
independently controlled from the point of view of EAPOL exchanges and authorization state. The Switch learns each
attached devices' individual MAC addresses, and effectively creates a logical Port that the attached device can then
use to communicate with the LAN via the Switch.
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