计网实验Computer Networking.docx

计网实验Computer Networking.docx

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计网实验ComputerNetworking

《计算机通信与网络实验》

课程实验报告

实验三:

ComputerNetworking

实验名称：

ComputerNetworking

LearningObjectivevs

Atcompletionofthislab,youwillbeableto:

1.Understandtheuseofcross-overandstraight-throughcablesfornetworking

2.FormasimplestEthernetwithtwocomputers

3.FormaswitchedEthernet

4.ConfigureTCP/IPparametersforthehostsandverifyconnectivityonthenetwork

5.ConfigurethenetworktoallowInternetsharing

ReportandFeedbackonthislab

Answerallquestionswithsupportingscreenshots.Pleasealsofillinthefollowingfeedbackformandappendittothereport.Yourfeedbackisvaluabletoussothatwecanimprovethislab,andmakethelabbetter.

Foreachtask,pleaseratethefollowinginthescaleof1through5:

∙Thedegreeofdifficulty:

1=tooeasy;5=toodifficult

∙Thelearningexperience:

1=learnednothing;5=learnedalot

∙Yourinterest:

1=nointerest;5=highinterest

∙Timeusedforthetask:

inminutes

Task

Difficulty（1—5）

Learning（1—5）

Interest（1—5）

Time（min）

background

Task1

Task2

Task3

Yoursuggestion/comment:

Background

Youneedtoreadandanswerthequestionsinthisbackgroundpartbeforethelab.Thislabhastobedoneinagroupof2or3persons.

Toformanetworkfordatacommunications,itisnecessarytoknowhowtoconnecthosts（computers）tothenetworkintermediatedevice（switch,router）andhowtointerconnectintermediatedevices.ReadmoreontheminLecture07.

Question1:

Explainwhatarecross-overandstraight-throughEthernetcables?

Howaretheyusedinnetworkconnections?

交叉线是把网线的TX和RX互换，即两个RJ45网口接收1~发送2，接收2~发送1。

交叉线一般用于相同设备的连接。

直连线是标准的网线，需要连接交换机使用，用于不同设备之间。

PingandTraceroute（tracert）aretwoimportantandusefulutilitytoolsfornetworktestinganddebugging.Readmoreonthemandlearnhowtousethem:

∙MSWindowspingcommand,

∙MSWindowstracertcommand,

Foreachhostorrouter,thereisaroutingtablethatguidestheIPdeliveryandforwarding.Readmoreonroutingtable（forwardingtable）inLecture15,andlearnhowtogettheroutingtableonahostrunningMSWindows,howtointerprettheroutingtable.IfyoucouldnotreachInternet,firstthingyoushoulddoistochecktheroutingtable.

∙MSWindowsroutecommand

Question2:

howtogettheroutingtable?

Includetheroutingtableonyourlaptopcomputerinthereport.Fromtheroutingtable,tellwhatyourcomputerIPaddressanddefaultgatewayIPaddressare.

WhenyouidentifyahostontheInternet,youusuallyusethedomainnameorhostname.ButifyoudonotconfigurethelocaldomainnameserverIPaddresscorrectly,youwouldnotbeabletousedomainnameservicefornameresolution.

InMSWindows,youcanuseIPconfigcommandtodisplayallcurrentTCP/IPnetworkconfiguration.

∙MSWindowsIPconfigcommand

Question3:

HowtofindyourlocaldomainnameserverIPaddresses?

Whataretheseaddressesconfiguredonyourcomputer?

HowtoconfigurethelocalDNSserveraddressesinMSWindows?

Task1.SimplestEthernetImplementation

Inthistask,youdonotneedtousewirelessLAN.SoyoucandisableWiFionbothlaptops.

Hardwareusedinthistask:

2laptopsand1cross-overEthernetcable

Useacross-overcabletoconnect2laptopstoeachotherthroughtheirEthernetports,asshownbelow:

Question4:

WhataretheIPaddressandnetworkmaskoneachEthernetadapter?

Usecommandpingtotesttheconnectivity.Thatis,ononecomputerrunpingtoverifythatitcanreachtheothercomputer.Ifitcannotreachtheothercomputer,youneedtotroubleshoot:

∙Makesurethatyouhaveturnedoffthewindowsfirewalloneachcomputer

∙VerifythecorrectIPaddressesfortheEthernetadaptersonbothcomputers.Theyhavetobeonthesamenetwork.

∙Makesurethatacross-overcableisused（onewithredcolorontheplug）

Whentheconnectivityisestablished,youcanrunAreaServerononecomputer,andrunAreaClientontheothercomputer.Youcanalsoruntheclient-Serverapplicationsonthesetwocomputers.YoucanrunWireSharktoeasilycaptureandanalyzethepacketsonthissimplestEthernet,sinceitwouldnothavesomuchdatatraffic.

Question5:

Whenthenetworkisworking,whatareIPaddressandnetworkmaskoneachcomputer?

主机信息：

IPV4地址变掉了

客户端地址没变

Question6:

Givetheroutingtableoneachcomputer.

Task2InternetSharing

ThistaskcontinuestheworkonEthernet.NowactivateWiFiononelaptop（calleditlaptopA）.StartawebbrowsertotestifyoucanreachInternetfromthislaptop.Ifnot,fixthewirelessInternetaccessfirstforthiscomputer.

ThenconfiguretheInternetsharingforthisWirelessconnectiontoallowothercomputersintheEthernettosharetheconnection.OnmyMSWindows7,Ididthesettings。

Whenyouenablethesharing,youwillbetoldthatanewIPaddressisassignedtoyourEthernetadapter.YoucanwritedownthisIPaddress.

Ontheotherlaptop（laptopB）,youneedtodisabletheEthernetconnection,andthenre-activatetheEthernetconnectiontoallowanewIPaddressinthesamenetworktobeassigned.

RunpingcommandonlaptopBtotestifyouareabletoreacheachother.Ifnot,youneedtodotroubleshootingandfixtheproblem（bycheckingifIPaddressesforbothEthernetadaptersareinthesamenetwork）.

Question7:

WhatareIPaddressandnetworkmaskforeachEthernetadapteroneachcomputer?

Then,startawebbrowseronlaptopB.TestifyouareabletoviewahomepageonInternet（bysharingtheWiFiInternetaccessontheotherlaptop）.Ifyoucouldnot,youmaycheckfollowings:

∙Usepingtotestifyouareabletoreach192.168.156.101（thatisthemoodleserver）.Ifyouabletoreachit,itmeansthatInternetsharingworks.Otherwise,youneedtotroubleshootthesharingandIPconfigurations.

∙CheckthelocalDNSserverIPaddressesforbothEthernetconnectionstomakesurethattheyarecorrect（youfindourlocalDNSserveraddressesinQuestion3）.

Question8:

whatareIPaddress,addressmask,andDNSserveraddressforeachEthernetconnection?

Question9:

GivetheroutingtableonlaptopB.WhatisthedefaultgatewayforlaptopB.Explainhowitispossibletosendapacketto192.168.156.101.

Task3SwitchedEthernet

Inthistask,weusealayer-2switchtofromaswitchedEthernet.Theswitchweuseinthelabis.Youcanreadmoreonitfromtheinstallationguideinthebox.

Eachgroupneedstohavesomecablesandoneswitchthatallowsupto8computersfortheconnectionstoformaswitchedEthernet.Connecteachlaptoptoaswitchportwithacableandthenconnectthepoweradpatertotheswitch.Theswitchednetworklooksasbelow.

Question10:

shouldacross-overcableorstraight-throughcablebeusedtoconnectacomputertotheswitch?

cross-overcable（交叉线）不可以

straight-throughcable（直连线）可以

Infact,somenewintermediatedevicesareintelligentandtheycandetectthecabletypestointernallyadjustthemselvestothecableused.Theswitchweuseisintelligentorsmart.Youcanusecross-overcableforconnectingthehosttotheswitch.

TestthenetworkconnectivitybyusingpingcommandandusingwebbrowserforInternetsharing.Ifitisnotok,dothetroubleshootingandfixtheproblem.Listtheproblemsyouencounteredandhowyousolvetheproblemsinthereporttoo.

Question11:

WhatareIPaddressandaddressmaskfortheEthernetadapteroneachcomputer?

Question12:

Inaswitchednetwork,cananyhostcapturethepacketssentbyanyotherhost?

Whyorwhynot?

可以

Ifyouwanttoincreasethenetworksize,youcaninterconnectswitches.Forexample,with2switches,youareabletoformaswitchednetworkwith14computers.

Question13:

shouldacross-overcableorstraight-throughcablebeusedtoconnectaswitchtoanotherswitch?