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.

36 posts

802.1X

Troubleshooting 802.1X with show authentication sessions and debug Commands

show authentication sessions is your first 802.1X diagnostic. Here is how to read the output, when to escalate to debug dot1x and debug radius, and how to stay sane.

Mar 24, 2026 10 min read

802.1X

dACL Not Applying Correctly in 802.1X: Troubleshooting Downloadable ACLs

dACL not applying usually means ISE sent the wrong AVPair name, the switch cannot download it, or the ACL content parsed badly. Here is the full troubleshooting path.

Mar 24, 2026 10 min read

802.1X

Dynamic VLAN Assignment Not Working in 802.1X: Troubleshooting Guide

Dynamic VLAN not working breaks down to four causes: ISE not sending Tunnel attributes, wrong values, switch not processing them, or VLAN not in the database. Here is how to isolate.

Mar 24, 2026 10 min read

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