单项选择题 How does using the service password encryption command on a router provide additional security?（）

多项选择题 A network administrator wants to ensure that only the server can connect to port Fa0/1 on a Catalyst switch. The server is plugged into the switch Fa0/1 port and the network administrator is about to bring the server online. What can the administrator do to ensure that only the MAC address of the server is allowed by switch port Fa0/1 (Choose two.)（）。

多项选择题 Which two are features of IPv6？（）