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. after broken links are re-established B. in an improperly implemented redundant topology C. when upper-layer protocols require high reliability D. during high traffic periods E. when a dual ring topology is in use
单项选择题 Which command sets and automatically encrypts the privileged enable mode password?（）
单项选择题 Which statement is true?（）
单项选择题 When upgrading the IOS image, the network administrator receives the exhibited error message. What could be the cause of this error?（）
