In the use of 802.1X access control，
which three protocols are allowed through the switch port  before authentication takes place？ （）

A. DAI can be performed on ingress ports only.
B. DAI can be performed on both ingress and egress ports.
C. DAI is supported on access ports， trunk ports， EtherChannel ports， and private VLAN ports.  
D. DAI should be enabled on the root switch for particular VLANs only in order to secure the ARP  caches of hosts in the domain.
E. DAI should be configured on all access switch ports as untrusted and on all switch ports connected to other switches as trusted.
F. DAI is supported on access and trunk ports only.

A. TACACS+ is the only supported authentication server type.
B. If a host initiates the authentication process and does not receive a response， it assumes it is  not authorized.
C. RADIUS is the only supported authentication server type.
D. Before transmitting data， an 802.1x host must determine the authorization state of the switch.
E. Hosts are required to havea 802.1x authentication client or utilize PPPoE.
F. None of the other alternatives apply.

A. The switch will uniquely authorize the client by using the client MAC address.
B. The switch will cause the port to remain in the unauthorized state， ignoring all attempts by the  client to authenticate.
C. The switch port will disable 802.1x port-based authentication and cause the port to transition to  the authorized state without any further authentication exchange.
D. The switch port will enable 802.1x port-based authentication and begin relaying authentication  messages between the client and the authentication server.