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.

MAC-Based Network Access Control

Uncontrolled Port

Controlled Port - port blocked

802.1X

Client

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.

Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch

802.1X Client

Figure 6- 73. Example of Typical Port-Based Configuration

AT-9724TS Switch

802.1X

Client

Figure 6- 74. Example of Typical MAC-Based Configuration

AT-9724TS Switch

802.1X Client

802.1X Client 802.1X Client

802.1X