D-Link DGS-3324SR User Manual - Access Control

xStack DGS/DXS-3300 Series Layer 3 Stackable Gigabit Ethernet Switch User Manual 

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Understanding 802.1x Port-based and MAC-based Network 

Access Control 

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 

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802.1X

Client

802.1X

Client

802.1X

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802.1X

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802.1X

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802.1X

Client

802.1X

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802.1X

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802.1X

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Network access controlled port

Network access uncontrolled port

RADIUS

Server

Ethernet Switch

Figure 6- 100. Example of Typical Port-Based Configuration 

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.