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Guest and Authentication-Fail VLANs
Typically, the authenticator (the Dell system) denies the supplicant access to the network until the supplicant is authenticated.
If the supplicant is authenticated, the authenticator enables the port and places it in either the VLAN for which the port is
configured or the VLAN that the authentication server indicates in the authentication data.
NOTE: Ports cannot be dynamically assigned to the default VLAN.
If the supplicant fails authentication, the authenticator typically does not enable the port. In some cases this behavior is not
appropriate. External users of an enterprise network, for example, might not be able to be authenticated, but still need access
to the network. Also, some dumb-terminals, such as network printers, do not have 802.1X capability and therefore cannot
authenticate themselves. To be able to connect such devices, they must be allowed access the network without compromising
network security.
The Guest VLAN 802.1X extension addresses this limitation with regard to non-802.1X capable devices and the Authentication-
fail VLAN 802.1X extension addresses this limitation with regard to external users.
● If the supplicant fails authentication a specified number of times, the authenticator places the port in the Authentication-fail
VLAN.
● If a port is already forwarding on the Guest VLAN when 802.1X is enabled, the port is moved out of the Guest VLAN and the
authentication process begins.
Configuring a Guest VLAN
If the supplicant does not respond within a determined amount of time ([reauth-max + 1] * tx-period, the system assumes that
the host does not have 802.1X capability and the port is placed in the Guest VLAN.
NOTE: For more information about configuring timeouts, refer to Configuring Timeouts.
Configure a port to be placed in the Guest VLAN after failing to respond within the timeout period using the dot1x guest-
vlan command from INTERFACE mode. View your configuration using the show config command from INTERFACE mode or
using the show dot1x interface command from EXEC Privilege mode.
Example of Viewing Guest VLAN Configuration
DellEMC(conf-if-gi-2/1)#dot1x guest-vlan 200
DellEMC(conf-if-gi 2/1))#show config
!
interface GigabitEthernet 2/1
switchport
dot1x guest-vlan 200
no shutdown
DellEMC(conf-if-gi 2/1))#
Configuring an Authentication-Fail VLAN
If the supplicant fails authentication, the authenticator re-attempts to authenticate after a specified amount of time.
NOTE:
For more information about authenticator re-attempts, refer to Configuring a Quiet Period after a Failed
Authentication.
You can configure the maximum number of times the authenticator re-attempts authentication after a failure (3 by default),
after which the port is placed in the Authentication-fail VLAN.
Configure a port to be placed in the VLAN after failing the authentication process as specified number of times using the
dot1x auth-fail-vlan command from INTERFACE mode. Configure the maximum number of authentication attempts by
the authenticator using the keyword max-attempts with this command.
Example of Configuring Maximum Authentication Attempts
DellEMC(conf-if-gi-2/1)#dot1x guest-vlan 200
DellEMC(conf-if-gi 2/1)#show config
!
interface GigabitEthernet 2/1
switchport
dot1x authentication
92
802.1X