单项选择题
A.ip sla 1 icmp-echo 1.1.1.1 tos 160
B.ip sla 1 icmp-echo 1.1.1.1 tos 20
C.ip sla 1 icmp-echo 1.1.1.1 precedence 5
D.ip sla 1 icmp-echo 1.1.1.1 dscp 20
单项选择题 YouarethenetworkadministratorofanenterprisecompanythatjustdeployedaglobalIPtelephonyenvironment.Inordertoguaranteegoodvoicequality，youaskedyourprovidertoimplementQoSonthe CEroutersofyourMPLSnetwork.OnyourLAN，youhavealsodeployedQoS.Users，however，keepcomplainingaboutbadvoicequality，andtheproviderdoesnotseematchesonthe DSCPvaluesthatyouhaveaskedhimtomatchupon.Whatismostlikelytheproblem？（）
单项选择题 YouarethenetworkadministratorofaLayer3switchednetwork.UsersinoneVLANarecomplainingthataccesstotheserverVLANisveryslowfromtimetotime.TrafficinthelocalVLANworkswithoutanyissue，andusersinotherVLANsdonothaveanycomplainttoreachtheserverVLAN.Whatismostlikelythecauseofthisissue？（）
单项选择题 Youaredeployingtwocoreswitches，oneineachbuilding，50kmawayfromeachother.Thecross-connectionbetweenthemwillbeaLayer22-gigabitEtherChannelwithan802.1Qtrunk.Youconfigureditcorrectlybutthelinkdoesnotcomeup.Theportisinthe"adminup"state，andthelineprotocolisinthe"down"state.ThefiberlinkisOK.Whatwouldbethemostlikelyreasonforthelinknottocomeup？（）