What Is 802.1X?
802.1X is a standard for port-based network access control — it authenticates a device before letting it onto the network. Plug into a switch port or Wi-Fi and 802.1X blocks all traffic until you prove your identity to a RADIUS server.
The three roles
- Supplicant — the device (laptop, phone) requesting access.
- Authenticator — the switch or access point controlling the port; it relays credentials but decides nothing itself.
- Authentication server — a RADIUS server that verifies the credentials and tells the authenticator to allow or deny.
Until the server says yes, the port passes only authentication traffic (EAP) — everything else is blocked.
Why it matters
802.1X stops unauthorised devices from getting a foothold just by plugging in. It is the enforcement layer of AAA at the edge, widely used in enterprises and campuses, and pairs with dynamic VLAN assignment so a user lands in the right VLAN automatically.
802.1X vs port security
Port security limits which MAC addresses a port accepts — simple but spoofable. 802.1X authenticates the actual user/device against a server — far stronger. Many networks use both.
Frequently asked questions
What is 802.1X?
A standard for port-based network access control that authenticates a device before allowing it onto the network. The port stays blocked to normal traffic until a RADIUS server verifies the credentials.
What are the three components of 802.1X?
The supplicant (the device requesting access), the authenticator (the switch or access point controlling the port), and the authentication server (usually RADIUS) that verifies credentials.
What is the difference between 802.1X and port security?
Port security filters by MAC address, which can be spoofed. 802.1X authenticates the actual device or user against a server, providing much stronger access control.
What protocol does 802.1X use?
It uses EAP (Extensible Authentication Protocol) between the supplicant and authenticator, and RADIUS between the authenticator and the authentication server.
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