计算机网络理论教学资料chapter4_网络层

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1、4.4IP地址以及IP地址的获取1.IP地址的获取流程ICANN-TISP-T网管-刁个人主机©ICANNTISPICANN(InternetCorporationforAssignedNameandNumbers)因特网名字与号码分配机构(非营利)工作内容：■allocatesaddresses分配IP地址■managesDNS管理DNS根服务器■assignsdomainnames,resolvesdisputes分配域名、解决域名纷争②ISPT网管Hierarchicaladdressing：m

2、orespecificroutesISPs-R・UshasamorespecificroutetoOrganization1Organization0Organization22OO.23.2O.O/23Fly-By-Night-1SP"Sendmeanythingwithaddressesbeginning200.23.16.0/20"Organization7:2OO.23.3O.O/23InternetISPs-R-UsOrganization1—//2OO.23.18.O/23/"Sendme

3、anythingwithaddressesbeginning199.31.0.0/16or200.23.18.0/23"^2231.1.1serverdst:255.255.255.255src:0.0.0.0223.1.2223.1.1.3223.13.27丄223.1.3.1arrivingDHCPclientneedsaddressinthisnetworkStep2.DHCPoffer223.1.3.1服务器响应.但因鄰^黑磬饉矗src:223.1.2.5所以只好serveJ223.1.21•

4、273.1.3.2arrivingDHCPclientneedsaddressinthisnetworkyiaddrr223124推荐可使用的IP（及掩码）IP地址阻用期leasetime:几天或几③（网管T）个人主机IP地址的分配方法一、网管手动配置方法二、自动配置：DHCP动态主机配置协议DynamicHostConfigurationProtocol即插即用plug-and-playStepl.DHCPdiscover找至UDHCP月艮务器3.1.1.2223.1.2.5DHCP

5、

6、server

7、223.1.2.1请求回显配芒参数dst:223.1.2.5src:223.1.2.4223.1.3.1Step4.DHCPACK223,1^eljarrivingDHCPclientneedsaddressinthisnetworkStep3.DHCPrequestIMl223.1.1DHCPserver223.1.2.1响应,并证实所请求的参数3.1.1.2dst:223.1.2.47Q223.L24src.233.1.2.5223.1.3.1223.12.3.27*-223.1.3.2arriv

8、ingDHCPclientneedsaddressinthisnetwork138.76.29.70.0.0.47®'—10.0.0.22.NAT网络地址转换(NetworkAddressTranslation)引入：子网内存在ip地址相同的情况，该如何沟通？①介绍：localnetworkusesjustoneIPaddressasfarasoutsideworldisconcerned子艮内部只由f1P1也址作为出口解决问题：■■■■rangeofaddressesnotneededfromISP

9、:justoneIPaddressforalldevicescanchangeaddressesofdevicesinlocalnetworkwithoutnotifyingoutsideworldcanchangeISPwithoutchangingaddressesofdevicesinlocalnetworkdevicesinsidelocalnetnotexplicitlyaddressable,visiblebyoutsideworld(asecurityplus)・②具体实现：A.替换（o

10、utgoing、incoming）B.记录21NATrouterchangesdatagramsourceadd厂from100.0.1,3345to133.76.29.7,5001,updatestableNATtranslationtableWANsideaddrLAZsideaddr138.76.29.7,500；・・・”—10.0.0.1,3345hhort10.0.0.1sendsdatagramto128.119.40.186,80I5：1