单项选择题
A.VACLs and VSPAN
B.RSPAN
C.ERSPAN
D.NetFlow
单项选择题 WhichofthefollowingdescribestheappropriateportassignmentandmessageexchangeinastandardTFTPtransaction？（）
问答题 网络安全涉及到TCP/IP哪几层？
单项选择题 Youaredeployingtwocoreswitches，oneineachbuilding，50kmawayfromeachother.Thecross-connectionbetweenthemwillbeaLayer22-gigabitEtherChannelwithan802.1Qtrunk.Youconfigureditcorrectlybutthelinkdoesnotcomeup.Theportisinthe"adminup"state，andthelineprotocolisinthe"down"state.ThefiberlinkisOK.Whatwouldbethemostlikelyreasonforthelinknottocomeup？（）