Critical VLAN
The 802.1X critical VLAN on a port accommodates 802.1X users that have failed authentication because none of the RADIUS servers in their ISP domain are 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 access device handles VLANs on an 802.1X-enabled port based on its 802.1X access control method.
For port-based access control
Authentication status | VLAN manipulation |
|---|---|
A user accesses the port and 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 reason other than 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. | The device assigns the authorization VLAN of the user to the port as the PVID, and it removes the port from the 802.1X critical VLAN. If the authentication server (either the local access device or a RADIUS server) does not authorize a VLAN, the initial PVID of the port applies. The user and all subsequent 802.1X users are assigned to this port VLAN. After the user logs off, the guest VLAN ID becomes the PVID. If no 802.1X guest VLAN is configured, the initial PVID of the port is restored. |
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 that 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. |
For MAC-based access control
Authentication status | VLAN manipulation |
|---|---|
A user accesses the port and fails 802.1X authentication because all the RADIUS servers are unreachable. | The device maps the MAC address of the user to the 802.1X critical VLAN. The user 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 user is still in the critical VLAN. |
A user in the 802.1X critical VLAN fails 802.1X authentication for any reason other than unreachable servers. | If an 802.1X Auth-Fail VLAN has been configured, the device remaps the MAC address of the user to the Auth-Fail VLAN ID. If no 802.1X Auth-Fail VLAN has been configured, the device remaps the MAC address of the user to the initial PVID. |
A user in the 802.1X critical VLAN passes 802.1X authentication. | The device remaps the MAC address of the user to the authorization VLAN. If the authentication server (either the local access device or a RADIUS server) does not authorize a VLAN to the user, the device remaps the MAC address of the user to the initial PVID on the port. |
A user in the 802.1X guest VLAN fails authentication because all the RADIUS servers are unreachable. | The device remaps the MAC address of the user to the 802.1X critical VLAN. The user can access only resources in the 802.1X critical VLAN. |
A user in the 802.1X Auth-Fail VLAN fails authentication because all the RADIUS servers are unreachable. | The user remains in the 802.1X Auth-Fail VLAN. |
When a reachable RADIUS server is detected, the device performs the following operations:
If MAC-based access control is used, the device removes 802.1X users from the critical VLAN. The port sends a unicast EAP-Request/Identity to these users to trigger authentication.
If port-based access control is used, 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.