# What is IEEE 802.1X Authentication?

> IEEE 802.1X authentication is the use of the IEEE 802.1X port-based network access-control standard to authenticate and authorize a device or user before granting normal access through a wired or wireless local area network port.

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## Content

The architecture separates the endpoint seeking access, the network device controlling the port, and the system that evaluates the authentication exchange and policy.

The endpoint, often called a supplicant or peer, exchanges Extensible Authentication Protocol (EAP) messages with an authenticator such as a switch or wireless access point. The authenticator may evaluate a method locally, but commonly relays the exchange to a backend authentication server using an AAA protocol such as RADIUS. Policy can then deny access or assign a permitted network segment and other controls.

### Key points

- **Endpoint role:** Presents an identity and participates in an EAP method, which may use certificates, passwords within a protected tunnel, or another supported credential.
- **Authenticator role:** Controls the logical port and passes EAP messages or locally performs authentication; it is not necessarily the system that validates the credential.
- **Backend role:** Validates the EAP exchange and returns an outcome and, where supported, authorization attributes to the authenticator.
- **Important limitation:** Successful 802.1X authentication is an admission decision, not proof that the endpoint is healthy or subsequent traffic is safe. Data protection requires appropriate wireless security or link encryption, and continuing access still needs segmentation and monitoring.

### Related terms

[Network access control (NAC)](<https://yellowcube.eu/glossary/network-access-control/>) · [Remote Authentication Dial-In User Service (RADIUS)](<https://yellowcube.eu/glossary/remote-authentication-dial-in-user-service/>) · [Authentication](<https://yellowcube.eu/glossary/authentication/>) · [Authorization](<https://yellowcube.eu/glossary/authorization/>) · [Network segmentation](<https://yellowcube.eu/glossary/network-segmentation/>)

### Sources

[IEEE 802.1X-2020: Port-Based Network Access Control](https://standards.ieee.org/ieee/802.1X/7345/) · [IETF RFC 3748: Extensible Authentication Protocol](https://www.rfc-editor.org/info/rfc3748)

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