单项选择题
What is the function of the command switchport trunk native vlan 999 on a switch?（）
A. It designates VLAN 999 for untagged traffic. B. It blocks VLAN 999 traffic from passing on the trunk. C. It creates a VLAN 999 interface. D. It designates VLAN 999 as the default for all unkown tagged traffic.
单项选择题 Which IPsec security protocol should be used when confidentiality is required?（）
单项选择题 Which command can you use to manually assign a static IPV6 address to a router interface?（）
单项选择题 Why will a switch never learn a broadcast address?（）
