Cisco Catalyst 2960 Series, Configuration Manual

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After a port moves to the restricted VLAN, a simulated EAP success message is sent to the client. This prevents
clients from indefinitely attempting authentication. Some clients (for example, devices running Windows XP)
cannot implement DHCP without EAP success.
Restricted VLANs are supported on 802.1x ports in all host modes and on Layer 2 ports.
You can configure any active VLAN except an RSPAN VLAN, a primary private VLAN, or a voice VLAN
as an 802.1x restricted VLAN. The restricted VLAN feature is not supported on internal VLANs (routed
ports) or trunk ports; it is supported only on access ports.
Other security port features such as dynamic ARP Inspection, DHCP snooping, and IP source guard can be
configured independently on a restricted VLAN.
802.1x Authentication with Inaccessible Authentication Bypass
Use the inaccessible authentication bypass feature, also referred to as critical authentication or the AAA fail
policy , when the switch cannot reach the configured RADIUS servers and new hosts cannot be authenticated.
You can configure the switch to connect those hosts to critical ports.
When a new host tries to connect to the critical port, that host is moved to a user-specified access VLAN, the
critical VLAN . The administrator gives limited authentication to the hosts.
When the switch tries to authenticate a host connected to a critical port, the switch checks the status of the
configured RADIUS server. If a server is available, the switch can authenticate the host. However, if all the
RADIUS servers are unavailable, the switch grants network access to the host and puts the port in the
critical-authentication state, which is a special case of the authentication state.
Inaccessible Authentication Bypass Support on Multiple-Authentication Ports
When a port is configured on any host mode and the AAA server is unavailable, the port is then configured
to multi-host mode and moved to the critical VLAN. To support this inaccessible bypass on
multiple-authentication (multiauth) ports, use the
authentication event server dead action reinitialize vlan
vlan-id command. When a new host tries to connect to the critical port, that port is reinitialized and all the
connected hosts are moved to the user-specified access VLAN.
This command is supported on all host modes.
Inaccessible Authentication Bypass Authentication Results
The behavior of the inaccessible authentication bypass feature depends on the authorization state of the port:
• If the port is unauthorized when a host connected to a critical port tries to authenticate and all servers
are unavailable, the switch puts the port in the critical-authentication state in the RADIUS-configured
or user-specified access VLAN.
• If the port is already authorized and reauthentication occurs, the switch puts the critical port in the
critical-authentication state in the current VLAN, which might be the one previously assigned by the
RADIUS server.
• If the RADIUS server becomes unavailable during an authentication exchange, the current exchange
times out, and the switch puts the critical port in the critical-authentication state during the next
authentication attempt.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
1341
Information About 802.1x Port-Based Authentication