802.1X

Port-based network access control, the standard for authenticating users and devices onto wired and wireless networks. Articles tagged 802.1X cover supplicant and authenticator behavior, RADIUS, EAP methods, Cisco ISE, dynamic VLANs, dACLs, host modes, and phased deployment.

33 posts

802.1X

RADIUS Server Unreachable in 802.1X: Causes and Fixes

When a switch marks ISE DEAD, every 802.1X port is affected. Here is how to confirm the outage fast, check shared secret and routing, and restore service.

Mar 24, 2026 10 min read

802.1X

Client Stuck in Unauthorized State: Diagnosing 802.1X Port Issues

A client stuck in Unauthorized covers five different failures: no EAPOL, supp timeout, dot1x missing, Access-Reject, or post-auth policy failure. Here is how to tell them apart.

Mar 24, 2026 9 min read

802.1X

802.1X Authentication Failing: Where to Start Troubleshooting

802.1X auth fails across four layers: endpoint, switch port, RADIUS, ISE policy. Jumping straight to ISE logs wastes time. Here is the structured way to isolate the layer.

Mar 24, 2026 9 min read

802.1X

Cisco TrustSec and SGTs: How They Integrate with 802.1X

TrustSec attaches a Security Group Tag to an 802.1X session, so segmentation policy follows identity through the network. Here is how SGT assignment integrates with ISE.

Mar 24, 2026 10 min read

802.1X

RADIUS Redundancy and Failover in 802.1X Deployments

Running Closed Mode 802.1X without RADIUS redundancy is asking for an outage. Here are the failure modes, the IOS XE config for multiple PSNs, and the verification.

Mar 24, 2026 11 min read

802.1X

Phased 802.1X Deployment Strategy for Enterprise Networks

Phased 802.1X deployments succeed when each phase is data collection first, enforcement second. Here is Phase 0 through Phase 4 with real endpoint discovery tactics.

Mar 24, 2026 11 min read