CCIE 350-001笔试题库

1、WhatisBGPsynchronization?A:Theruleofsynchronizationstatesthefollowing:BeforearoutelearnedfromanIBGPneighborisenteredintotheIProutingtableorisadvertisedtoaBGPpeer,theroutemustfirstbeknownviaIGP.2、whichBGPattributeswillinfluenceinboundflow?A:MED、AS-PATH，ORIGIN3、BGPAdministrativedistanceA：BGPhasadistancebgpcommandthatallowsyoutosetdifferentadministrativedistancesforthreeroutetypes:external,internal,andlocal.Externalroute20Internalroute200Localroute2004、WhichpictureisTrafficShape,why?A:Policingtypicallydropsexcesstraffic.Shapingsmoothtraffictoaspecificrateusingabuffer.5、Unequalcostload-sharingA:RouterEwillselectbothBandCasnexthoptoreachnetworkZ.Unequalcostloadsharinghappening.Thevariancecommandisusedtodeterminewhichroutesarefeasibleforunequal-costloadsharing.Variancedefinesamultiplierbywhichametricmaydiffer,orvary,fromthemetricofthelowest-costroute.Anyroutewhosemetricexceedsthemetricofthelowest-costroute,multipliedbythevariance,willnotbeconsideredafeasibleroute.Thedefaultvarianceisone,meaningthatthemetricsofmultipleroutesmustbeequal,toloadbalance.Variancemustbespecifiedinwholenumbers.Thefollowingthreeconditionsmustbemetforaroutetobeincludedinunequal-costloadsharing:Themaximum-pathslimitmustnotbeexceededasaresultofaddingtheroutetoaload-sharinggroup.Thenext-hoproutermustbemetricallyclosertothedestination.Thatis,itsmetricfortheroutemustbesmallerthanthelocalrouter'smetric.Anext-hoprouter,beingclosertothedestination,isoftenreferredtoasthedownstreamrouter.(加入负载均衡的下一跳的路由器必须要满足FC，即ADFD.Theadvertiseddistanceshouldbelowerthanfeasibledistance)Themetricofthelowest-costroutemultipliedbythevariance,mustbegreaterthanthemetricoftheroutetobeadded.EIGRP基本概念：（1）adjacency：Anadjacencyisalogicalassociationbetweentwoneighborsoverwhichrouteinformationisexchanged.Whenadjacencieshavebeenestablished,therouterwillreceiveupdatesfromitsneighbors.（2）feasibledistance(FD)：Thelowestcalculatedmetrictoeachdestinationwillbecomethefeasibledistance(FD)ofthatdestination.（3）feasibilitycondition(FC)：Thefeasibilitycondition(FC)isaconditionthatismetifaneighbor'sadvertiseddistance（AD）toadestinationislowerthantherouter'sFDtothatsamedestination.（4）feasiblesuccessor：Ifaneighbor'sadvertiseddistancetoadestinationmeetstheFC,theneighborbecomesafeasiblesuccessor[9]forthatdestination.TheconceptsoffeasiblesuccessorsandtheFCarecentraltoloopavoidance.（5）topologytable：alongwiththefollowingitems:Thedestination'sFDAllfeasiblesuccessorsEachfeasiblesuccessor'sadvertiseddistancetothedestinationThelocallycalculateddistancetothedestinationviaeachfeasiblesuccessor,basedonthefeasiblesuccessor'sadvertiseddistanceandthecostofthelinktothatsuccessorTheinterfaceconnectedtothenetworkonwhicheachfeasiblesuccessorisfound[10]（6）successor:Foreverydestinationlistedinthetopologicaltable,theroutewiththelowestmetricischosenandplacedintotheroutetable.Theneighboradvertisingthatroutebecomesthesuccessor,orthenext-hoproutertowhichpacketsforthatdestinationaresent.6、whatisforward-delay?A:ForwardDelayisthetimethatthebridgespendsinthespanningtreeListeningorLearningstates.7.r1andr2betweenaswitch,switchrunningSTPagreement,r1andr2runningeigrp,whenr1andswitchbetweenthelinkdown,r2knowhowtheneighborsdownoutr1？A：Holdtimeisusingtofindaneighbordown.Ifnohellopacketreceivedbeforeholdtimerexpires,r2willdeclarethatr1isdown.WhenarouterreceivesaHellopacketfromaneighbor,thepacketwillincludeaholdtime.TheholdtimetellstherouterthemaximumtimeitshouldwaittoreceivesubsequentHellos.IftheholdtimerexpiresbeforeaHelloisreceived,theneighborisdeclaredunreachableandDUALisinformedofthelossofaneighbor.Onmostnetworks,HellosaremulticasteveryfivesecondsOnmultipointX.25,FrameRelay,andATMinterfaces,withaccesslinkspeedsofT1orslower,Hellosareunicastevery60seconds.Bydefault,theholdtimeisthreetimestheHellointerval.180secondsforlow-speednonbroadcastmultiaccess(NBMA)networksand15secondsforallothernetworks.调整命令：(接口下)iphello-intervaleigrpiphold-timeeigrpEIGRPhello-time和hold-time不匹配也能建立邻居。8、Inarunsparse-dense-modemulticastnetwork,whenrendezvouspointdown,willtherecipientreceivethepacketssendbythesource?why?A:Insparse-dense-mode,ifthereisothercandidateRPsexist,oneofthecandidateRPwillbecomeRP,andrecipientcanalsoreceivemulticastpackets.IfnoRPisfoundforthisgroup,multicasttraffictothisgroupwillbeforwardedviadense-mode,andrecepientstillcanreceivethepackets.Sparse-densemode:IfamulticastgrouphasaknownRP,theinterfaceistreatedinsparsemode.IfagrouphasnoknownRP,bydefaulttheinterfaceistreatedindensemodeanddatawillbefloodedoveritsinterfaces.9、r1isthehub,multipointmodesubinterface,r2andr3isspoke,whenr2downatthespoke,Whatwillr1react?howaboutr3?A：R1willsetthePVCtor2asinactive.R3willnotbeaffected.whenr2downandtheframerelayswitch’skeepalivecountertimeout,theFrameRelayswitchdeclaresthePVCconnectiontotherouterR2asinactive.SoR1willsetthePVCasinactive.10.一个IPV6yIPV6的DEFAULT-GATE-WAY问题是当A收到了B发给C的数据包的时候，A会如何处理？(选择题)已知答案有2个选项，1）A会作出重定向2）A会直接丢弃A:drop（看情况，如果A收到数据包的MAC地址为C的地址，A会直接丢弃；如果A受到数据包的MAC地址为A的地址，A的路由表下一跳是C，并且重定向功能开启，A会将数据包进行重定向。）11,whatisRPF(ReversePathFor