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802.1X What is it?

802.1X is an authentication protocol to allow access to networks with the use of a RADIUS server. 802.1X and RADIUS based security is considered the gold standard to secure wireless and wired networks today.

IEEE 802.1X is an IEEE Standard for port-based network access control (PNAC). It is part of the IEEE 802.1 group of networking protocols. It provides an authentication mechanism to devices wishing to attach to a LAN or WLAN.

IEEE 802.1X defines the encapsulation of the Extensible Authentication Protocol (EAP) over wired IEEE 802 networks[1] and over 802.11 wireless networks,[2] which is known as "EAP over LAN" or EAPOL.[3] EAPOL was originally specified for IEEE 802.3 Ethernet, IEEE 802.5 Token Ring, and FDDI (ANSI X3T9.5/X3T12 and ISO 9314) in 802.1X-2001,[4] but was extended to suit other IEEE 802 LAN technologies such as IEEE 802.11 wireless in 802.1X-2004.[5] The EAPOL was also modified for use with IEEE 802.1AE ("MACsec") and IEEE 802.1AR (Secure Device Identity, DevID) in 802.1X-2010[6][7] to support service identification and optional point to point encryption over the internal LAN segment.


EAP data is first encapsulated in EAPOL frames between the Supplicant and Authenticator, then re-encapsulated between the Authenticator and the Authentication server using RADIUS or Diameter.
802.1X authentication involves three parties: a supplicant, an authenticator, and an authentication server. The supplicant is a client device (such as a laptop) that wishes to attach to the LAN/WLAN. The term 'supplicant' is also used interchangeably to refer to the software running on the client that provides credentials to the authenticator. The authenticator is a network device that provides a data link between the client and the network and can allow or block network traffic between the two, such as an Ethernet switch or wireless access point; and the authentication server is typically a trusted server that can receive and respond to requests for network access, and can tell the authenticator if the connection is to be allowed, and various settings that should apply to that client's connection or setting. Authentication servers typically run software supporting the RADIUS and EAP protocols. In some cases, the authentication server software may be running on the authenticator hardware.

The authenticator acts like a security guard to a protected network. The supplicant (i.e., client device) is not allowed access through the authenticator to the protected side of the network until the supplicant's identity has been validated and authorized. With 802.1X port-based authentication, the supplicant must initially provide the required credentials to the authenticator - these will have been specified in advance by the network administrator and could include a user name/password or a permitted digital certificate. The authenticator forwards these credentials to the authentication server to decide whether access is to be granted. If the authentication server determines the credentials are valid, it informs the authenticator, which in turn allows the supplicant (client device) to access resources located on the protected side of the network.[8]

Protocol operation
EAPOL operates over the data link layer, and in Ethernet II framing protocol has an EtherType value of 0x888E.

Port entities
802.1X-2001 defines two logical port entities for an authenticated port—the "controlled port" and the "uncontrolled port". The controlled port is manipulated by the 802.1X PAE (Port Access Entity) to allow (in the authorized state) or prevent (in the unauthorized state) network traffic ingress and egress to/from the controlled port. The uncontrolled port is used by the 802.1X PAE to transmit and receive EAPOL frames.

802.1X-2004 defines the equivalent port entities for the supplicant; so a supplicant implementing 802.1X-2004 may prevent higher-level protocols from being used if it is not content that authentication has successfully completed. This is particularly useful when an EAP method providing mutual authentication is used, as the supplicant can prevent data leakage when connected to an unauthorized network.

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