单项选择题
In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN（）。
A.during high traffic periods B.after broken links are re-established C.when upper-layer protocols require high reliability D.in an improperly implemented redundant topology E.when a dual ring topology is in use
单项选择题 There are no boot system commands in a router configuration in NVRAM. What is the fallback sequence that the router will use to find an IOS during reload（）。
单项选择题 Which type of EIGRP route entry describes a feasible successor?（）
多项选择题 以下哪两个安全工具能被安装在一个网络里？（）
