CCNA27englishWord文件下载.docx

CCNA27englishWord文件下载.docx

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3、WhatarethreeuniquecharacteristicsofUDP?

（Choosethree.）

connectionoriented

full-duplexoperation

lowoverhead低开销

noflowcontrol无流量控制

noerror-recoveryfunction错误不重传

reliabletransmission

4、WithinTCP,whatcombination组件makesupasocketpair对?

套接对

sourceportwithdestinationport

sourceIPaddresswithdestinationport

sourceIPaddressanddestinationIPaddress

sourceIPaddressandportwithadestinationIPaddressandport

5、Whattypeofupdateallowsclientcomputerstoregister注册andupdatetheirresourcerecords原纪录withaDNSserverwheneverchangesoccur?

dynamic

zonetransfer

localrecursivequery

rootdomainquery

top-leveldomainquery

6、WhichDNSzoneresolves解析anIPaddresstoaqualifieddomainname一个合格的域名?

dynamiclookup

forwardlookup

resolutionlookup

reverselookup反向查找

7、WhichtwotasksaretheresponsibilityofthelocalDNSserver?

（Choosetwo.）

maintainingalargenumberofcachedDNSentries

maintainingtheISPserver

mappingname-to-IPaddressesforinternalhosts内部主机的域名-IP映射

forwardingnameresolution解析requeststoacaching-onlyserver将域名解析请求转发至只有缓存功能的服务器

forwardingallnameresolutionrequeststorootserversontheInternet

8、Whichprotocolisusedtosende-mail,eitherfromaclienttoaserverorfromaservertoanotherserver?

SNMP

FTP

SMTP

HTTPS

9、AmanufacturingcompanysubscribestocertainhostedservicesfromtheirISP.Theservicesrequiredincludehostedworldwideweb,filetransfer,ande-mail.Whichprotocolsrepresentthesethreekeyapplications?

FTP

HTTP

DNS

SNMP

DHCP

SMTP

10、Tomeetcustomerexpectations满足客户期望,anISPmustguarantee确保alevelofservicethatisbasedonwhattwofactors?

accessibility

adaptability

availability可用性

reliability可靠性

scalability

11、WhichtwostatementsaretrueabouttheOSIandTCP/IPmodels?

ThetwobottomlayersoftheTCP/IPmodelmakeupthebottomlayeroftheOSImodel.

TheTCP/IPmodelisatheoreticalmodelandtheOSImodelisbasedonactualprotocols.

TheOSInetworklayeriscomparable相当于totheInternetlayeroftheTCP/IPmodel.

TheTCP/IPmodelspecifiesprotocolsforthephysicalnetworkinterconnection.

TheTCP/IPmodelisbasedonfourlayersandtheOSImodelisbasedonsevenlayers.

12、WhattypeofDNSserveristypicallymaintainedbyanISP?

caching-only缓存

root

second-level

top-level

13、Whichtwooptionscorrectlymatchprotocolandwell-knownportnumber协议和端口的匹配?

DNS-25

FTP-110

HTTP-80

POP3-25

SMTP-25

14、WhatarethreecharacteristicsofHTTPS?

Itusesadifferentclientrequest-serverresponseprocessthanHTTPuses.

Itspecifiesadditionalrulesforpassingdatabetweentheapplicationanddatalinklayers.

Itsupportsauthentication.

ItallowsmoresimultaneousconnectionsthanHTTPallows.

ItencryptspacketswithSSL.

Itrequiresadditionalserverprocessingtime.额外的服务器处理时间

15、User1issendingane-mailtoUser2@.Whataretwocharacteristicsoftheprocessofsendingthisdata?

ItutilizesTCPport110.

ATCPconnectionisestablisheddirectlybetweentheUser1andUser2clientcomputersinordertosendthee-mailmessage.

Itutilizes利用astoreandforwardprocess.使用存储转发

Thesameapplicationlayerprotocolisusedtosendthee-mailandretrieveitfromthedestinationserver.

SMTPisusedtosendthee-mailmessagetothemailservers.

16、WhichthreefieldsdoaTCPheaderandaUDPheaderhaveincommon?

sourceport

window

checksum校验和

destinationport

acknowledgmentnumber

sequencenumber

17、Whenahostiscommunicatingwithmultipleapplicationsonthesameserveratthesametime,whichtwovalueswilllikelybethesameinallpacketsforeachsession?

那个保持一致的（Choosetwo.）

IPaddress

MACaddress

sessionnumber

18、Whatarethreecharacteristicsofnetworkreliability可用性?

Redundant冗余hardwareprovidesenhancedreliability.硬件冗余提供提高可靠性。

Reliabilityismeasuredbasedonthenumberofapplicationsinuseonthenetwork.

ThelongertheMTTR,thegreaterthereliability.

Faulttoleranceisameasureofreliability.可用容错能力来衡量可靠性

ThelongertheMTBF,thegreaterthereliability.

AnISPguaranteesthesamelevelofreliabilitytoallofitscustomers.

19、Refertotheexhibit.Host1isintheprocessofsettingupaTCPsessionwithHost2.Host1hassentaSYNmessagetobeginsessionestablishment.Whathappensnext?

Host1sendsanACKmessagetoHost2.

Host1sendsaSYNmessagetoHost2.

Host1sendsaSYN-ACKmessagetoHost2.

Host2sendsanACKmessagetoHost1.

Host2sendsaSYNmessagetoHost1.

Host2sendsaSYN-ACKmessagetoHost1.

20、Refertotheexhibit.ThePCisrequestingHTTPdatafromtheserver.Whatisavalidrepresentationofsourceanddestinationsocketsforthisrequest?

源和目的套接

Source-192.168.1.17:

80;

Destination-192.168.2.39:

80

1045

1045;

1061

21、Refertotheexhibit.Whichtwostatementsaretrueaboutthisfile?

Ifthegatewayaddresschanges,thefilewillbeupdateddynamically.

ThecommandpingfileservwilluseIPaddress172.16.5.10.

Ifthepingcommandisissued,thefilewillbecheckedfortheCiscowebserverIPaddressbeforeDNSisqueried.在进行DNS请求前，将检查该文件中的Ciscoweb服务器IP地址。

ThecommandpingmypcwilluseIPaddress172.16.5.1.

NametoIPaddressmappingsareaddedtothefileaftertheyarereceivedfromDNS.

22、WhichtwostatementsdescribetheFTPprotocol?

Ituseswell-knownport23.

Theprotocolinterpreterisresponsibleforthedatatransferfunction.

TheFTPclientinitiatesthetransferofdata会启动数据传输whenusingapassivedataconnection.

Itrequirestwoconnectionsbetweenclientandserver.

FTPserversopenawell-knownportontheclientmachine.