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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.

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.

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.

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.

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.

Monitor Mode, Low-Impact Mode, and Closed Mode each trade visibility for enforcement. Here are the IOS XE configs, show output, and honest gaps for each mode.