单项选择题
Catalyst switches utilize a special technology to identify and prevent topology loops and ensure that data flows properly through a single network path. What is the name of this technology?（）
A. VTP B. ISL C. 802.1Q D. STP E. None of the above
多项选择题 Which fields are included in the TCP header?（）
单项选择题 How many simultaneous Telnet sessions does a Cisco router support by default?（）
单项选择题 Which of the following protocols use both TCP and UDP ports?（）
