Critical VLAN
The 802.1X critical VLAN on a port accommodates 802.1X users who have failed authentication because none of the RADIUS servers in their ISP domain is reachable. Users in the critical VLAN can access a limited set of network resources depending on the configuration.
The critical VLAN feature takes effect when 802.1X authentication is performed only through RADIUS servers. If an 802.1X user fails local authentication after RADIUS authentication, the user is not assigned to the critical VLAN. For more information about the authentication methods, see "Configuring AAA."
The 802.1X critical VLAN takes effect only on a port that performs port-based access control.
The following table describes how the access device handles VLANs on an 802.1X-enabled port that performs port-based access control:
Authentication status | VLAN manipulation |
|---|---|
A user that has not been assigned to any VLAN fails 802.1X authentication because all the RADIUS servers are unreachable. | The device assigns the critical VLAN to the port as the PVID. The 802.1X user and all subsequent 802.1X users on this port can access only resources in the 802.1X critical VLAN. |
A user in the 802.1X critical VLAN fails authentication because all the RADIUS servers are unreachable. | The critical VLAN is still the PVID of the port, and all 802.1X users on this port are in this VLAN. |
A user in the 802.1X critical VLAN fails authentication for any other reasons except for unreachable servers. | If an 802.1X Auth-Fail VLAN has been configured, the PVID of the port changes to the Auth-Fail VLAN ID, and all 802.1X users on this port are moved to the Auth-Fail VLAN. If no 802.1X Auth-Fail VLAN is configured, the initial PVID of the port is restored. |
A user in the 802.1X critical VLAN passes 802.1X authentication. |
|
A user in the 802.1X guest VLAN fails authentication because all the RADIUS servers are unreachable. | The device assigns the 802.1X critical VLAN to the port as the PVID, and all 802.1X users on this port are in this VLAN. |
A user in the 802.1X Auth-Fail VLAN fails authentication because all the RADIUS servers are unreachable. | The PVID of the port remains unchanged. All 802.1X users on this port can access only resources in the 802.1X Auth-Fail VLAN. |
A user who has passed authentication fails reauthentication because all the RADIUS servers are unreachable, and the user is logged out of the device. | The device assigns the 802.1X critical VLAN to the port as the PVID. |
The network device assigns a hybrid port to an 802.1X critical VLAN as an untagged member.
For more information about VLAN configuration, see Layer 2—LAN Switching Configuration Guide.
When a reachable RADIUS server is detected, the device removes the port from the critical VLAN. The port sends a multicast EAP-Request/Identity to all 802.1X users on the port to trigger authentication.