单项选择题
To which of these does IP multicast send packets?（）
A. a single host B. a subset of hosts C. all hosts sequentially D. all hosts simultaneously
单项选择题 Which of these ports does syslog use to send messages to a syslog server?（）
单项选择题 Which of these is a benefit of ESM?（）
单项选择题 How does ERS use the VLAN tag?（）
