网院答案24.docx

网院答案24.docx

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网院答案24

1

窗体顶端

Whicheventwillcauseatriggeredupdate?

anupdateroutingtimerexpires

acorruptupdatemessageisreceived

arouteisinstalledintheroutingtable

thenetworkisconverged

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption3

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.3.3TriggeredUpdates

2

窗体顶端

Threeroutersrunningadistance-vectorroutingprotocollostallpower,includingthebatterybackups.Whentheroutersreload,whatwillhappen?

TheywillshareallroutessavedinNVRAMpriortothepowerlosswiththeirdirectlyconnectedneighbors.

Theywillmulticasthellopacketstoallotherroutersinthenetworktoestablishneighboradjacencies.

Theywillsendupdatesthatincludeonlydirectlyconnectedroutestotheirdirectlyconnectedneighbors.

Theywillbroadcasttheirfullroutingtabletoallroutersinthenetwork.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption3

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.2.2InitialExchangeofRoutingInformation

3

窗体顶端

WhatdoestheRIPholddowntimerdo?

ensuresaninvalidroutehasametricof15

preventsarouterfromsendinganyupdatesafterithasintroducedaroutingloopintothenetwork

ensureseverynewrouteisvalidbeforesendinganupdate

instructsrouterstoignoreupdates,foraspecifiedtimeorevent,aboutpossibleinaccessibleroutes

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption4

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.4.4PreventingRoutingLoopswithHolddownTimers

4

窗体顶端

WhichtwostatementsaretrueregardingthefunctionoftheRIPv1routingupdates?

（Choosetwo）.

updatesarebroadcastonlywhentherearechangestothetopology

updatesarebroadcastatregularintervals

broadcastaresentto0.0.0.0

broadcastsaresentto255.255.255.255

updatescontaintheentirenetworktopology

onlychangesareincludedintheupdates

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

Option2andOption4arecorrect.

1pointforeachcorrectoption.

0pointsifmoreoptionsareselectedthanrequired.

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.1.2DistanceVectorTechnology

5

窗体顶端

WhichofthefollowingstatementsarecorrectaboutRIP?

usesabroadcasttoupdateallotherroutersinthenetworkevery60seconds

usesamulticastaddresstoupdateotherroutersevery90seconds

willsendoutanupdateifthereisafailureofalink

updatesonlycontaininformationaboutroutesthathavechangedsincelastupdate

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption3

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.3.1PeriodicUpdates:

RIPv1andIGRP

6

窗体顶端

WhichtwostatementsdescribeEIGRP?

（Choosetwo.）

EIGRPcanbeusedwithCiscoandnon-Ciscorouters.

EIGRPsendstriggeredupdateswheneverthereisachangeintopologythatinfluencestheroutinginformation.

EIGRPhasaninfinitemetricof16.

EIGRPsendsapartialroutingtableupdate,whichincludesjustroutesthathavebeenchanged.

EIGRPbroadcastsitsupdatestoallroutersinthenetwork.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

Option2andOption4arecorrect.

1pointforeachcorrectoption.

0pointsifmoreoptionsareselectedthanrequired.

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.3.2BoundedUpdates:

EIGRP

7

窗体顶端

Whichstatementistrueregardingcisco’sRIP_JITTERvariable?

Itpreventsthesynchronizationofroutingupdatesbybufferingtheupdatesastheyleavetherouterinterfaces.

Itpreventsthesynchronizationofroutingupdatesbysubtractingarandomlengthoftimerangingfrom0%to15%ofthespecifiedintervaltimefromthenextroutingupdateinterval.

Itpreventsthesynchronizationofroutingupdatesbycausingtheroutertoskipeveryotherscheduledupdatetime.

Itpreventsthesynchronizationofroutingupdatesbyforcingtheroutertolistenwhenitstimeforotherupdatesonthelinesbeforesendingitsupdate.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption2

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.3.4RandomJitter

8

窗体顶端

WhatactionswilloccurafterRouterAlosesconnectivitytonetwork114.125.16.0?

（Choosetwo.）

RouterBwillincludenetwork123.92.76.0and136.125.85.0initsupdatetoRouterA.

Duringthenextupdateinterval,RouterBwillsendaRIPupdateoutbothportsthatincludestheinaccessiblenetwork.

Duringthenextupdateinterval,RouterCwillsendanupdatetoRouterBstatingthatnetwork114.125.16.0isaccessiblein2hops.

RouterCwilllearnofthelossofconnectivitytonetwork114.125.16.0fromRouterB.

RouterBwillincludenetwork123.92.76.0and136.125.85.0initsupdatetoRouterC.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

Option1andOption4arecorrect.

1pointforeachcorrectoption.

0pointsifmoreoptionsareselectedthanrequired.

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.3.1PeriodicUpdates:

RIPv1andIGRP

9

窗体顶端

Whichofthefollowingmethodsdoessplithorizonusetoreduceincorrectroutinginformation?

Routingupdatesaresplitinhalftoreducetheupdatetime.

Informationlearnedfromonesourceisnotdistributedbacktothatsource.

Newrouteinformationmustbelearnedfrommultiplesourcestobeaccepted.

Thetimebetweenupdatesissplitinhalftospeedconvergence.

Newrouteinformationissuppresseduntilthesystemhasconverged.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption2

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.4.5SplitHorizonRule

10

窗体顶端

ThegraphicshowsanetworkthatisconfiguredtouseRIProutingprotocol.Router2detectsthatthelinktoRouter1hasgonedown.Itthenadvertisesthenetworkforthislinkwithahopcountmetricof16.Whichroutinglooppreventionmechanismisineffect?

splithorizon

errorcondition

hold-downtimer

routepoisoning

counttoinfinity

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption4

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.4.6SplitHorizonwithPoisonReverseorRoutePoisoning

11

窗体顶端

WhatisthepurposeoftheTTLfieldintheIPheader?

usedtomarkroutesasunreachableinupdatessenttootherrouters

preventsregularupdatemessagesfromreinstatingaroutethatmayhavegonebad

preventsarouterfromadvertisinganetworkthroughtheinterfacefromwhichtheupdatecame

limitsthetimeorhopsthatapacketcantraversethroughthenetworkbeforeitshouldbediscarded

definesamaximummetricvalueforeachdistancevectorroutingprotocolbysettingamaximumhopcount

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption4

0pointsforanyotheroption

2

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.4.7IPandTTL

12

窗体顶端

Whichofthefollowingcanexistinadistancevectornetworkthathasnotconverged?

（Choosethree.）

routingloops

inconsistenttrafficforwarding

notrafficforwardinguntilsystemconverges

inconsistentroutingtableentries

routingtableupdatessenttowrongdestinations

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

Option1,Option2,andOption4arecorrect.

1pointforeachcorrectoption.

0pointsifmoreoptionsareselectedthanrequired.

3

Thisitemreferencescontentfromthefollowingareas:

CCNAExploration:

RoutingProtocolsandConcepts

∙4.4.1DefinitionandImplications

13

窗体顶端

Refertotheexhibit.TheroutersinthisnetworkarerunningRIP.RouterAhasnotreceivedanupdatefromRouterBinoverthreeminutes.HowwillRouterArespond?

TheHolddowntimerwillwaittoremovetheroutefromthetablefor60seconds.

TheInvalidtimerwillmarktherouteasunusableifanupdatehasnotbeenreceivedin180seconds.

TheUpdatetimerwillrequestanupdateforroutesthatwerelearnedfromRouterB.

TheHellotimerwillexpireafter10secondsandtheroutewillbeflushedoutoftheroutingtable.

窗体底端

Observable

Description

MaxValue

1

correctnessofresponse

2pointsforOption2

0pointsforanyother