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Upon connecting a device to an ethernet port on a switch or associating to a wireless SSID, the network switch or wifi router concerned will initially not allow any data to be transmitted/received by the device. It will request the connected device to identify itself and, upon approval of the supplied credentials by an authentication server, start accepting packets from/to the newly connected device, or continue dis-allowing, in the case the authentication server did not approve the credentials.

Architecture

802.1X is the protocol that defines how EAP messages are transmitted over an IEEE 802 network (e.g. ethernet, wifi).

Things to mention:

What RADIUS/802.1X is able to provide and not and in which situations.

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