TCPIP協(xié)議原理英文版課件：Chapter 6 ARP and RARP

2022/10/29TCP/IPProtocolSuite1Chapter6ARPandRARPARPARPpackage（ARP軟件包）RARP2022/10/29TCP/IPProtocolSuite2兩級地址IP分組交付到主機或路由器需要兩級地址互連網(wǎng)級：邏輯地址標識主機/路由器全網(wǎng)統(tǒng)一編址，具有全局唯一性——全局地址所有與互聯(lián)網(wǎng)打交道的軟件都要使用邏輯地址在Internet中，邏輯地址就是IP地址（32bit）物理網(wǎng)級：物理地址標識主機/路由器本地范圍內(nèi)具有唯一性，但在整個互聯(lián)網(wǎng)內(nèi)不一定具有全局唯一性——本地地址分組需要通過物理網(wǎng)絡才能到達路由器或主機以太網(wǎng)中，物理地址就是MAC地址（48bit）2022/10/29TCP/IPProtocolSuite3MappingLogicaladdress(IP)PhysicaladdressNetworkDataLinkPhysicalMappingTo：電子科技大學成都市建設北路2段4號單位名稱（邏輯）單位地址（物理）2022/10/29TCP/IPProtocolSuite4IssuesA送往E的分組需封裝在Ethernet幀中傳送IP地址：全局性物理地址：本地性AA僅知道：IPA，MACA，IPEEthernetFrame：IPPacket？EBCD目的MAC類型FCS源MACMACA2022/10/29TCP/IPProtocolSuite5AddressMapping（地址映射）LogicaladdressPhysicaladdressStaticmapping

映射表固定設置DynamicmappingStaticTableLogicaladdressPhysicaladdress……………………Consider:NICchangedMobilecomputerCacheLogicaladdressPhysicaladdress……………………Lookforthetargetondemanding,usingdynamicAddressResolutionProtocol2022/10/29TCP/IPProtocolSuite6ARPandRARPARPLogicaladdressPhysicaladdressRARPLogicaladdressPhysicaladdress2022/10/29TCP/IPProtocolSuite7ARPAddressResolutionProtocol，RFC826地址解析協(xié)議：IPaddressMACaddressIPLANsMANsWANsICMPIGMPARPRARPNetworkLayerNetworkAccessLayerTransportLayerApplicationLayer2022/10/29TCP/IPProtocolSuite8ARPOperationA:E:I’mlookingforthephysicaladdressofanodewhoseIPaddressis:Iamthenodeyouarelookingfor,andmyphysicaladdressis:0005.5D06.1418RequestRequestRequestReplyRequestBroadcastUnicastB:C:D:IPaddressMACaddressA’sARPCache：0005.5D06.1418bind2022/10/29TCP/IPProtocolSuite9ARPCacheARPcacheTomaintaintherecent

mappingsfromlogicaladdresses(IP)tohardwareaddresses(MAC)典型存活時間：2minutesEssentialtotheefficientoperationofARP

舉例：主機ARPCacheC:>arp–aInterface:8---0x50002InternetAddress PhysicalAddress Type200-03-31-b5-50-00Dynamic2022/10/29TCP/IPProtocolSuite10用戶輸入命令“ftp主機名”時的操作FTPTCPIPARP以太網(wǎng)驅(qū)動程序主機名解析器以太網(wǎng)驅(qū)動程序以太網(wǎng)驅(qū)動程序主機名IP地址（1）（2）（3）（4）（6）ARPARPFTPTCPIP（5）（7）目的源2022/10/29TCP/IPProtocolSuite11ARPPacketHardwareTypeProtocolTypeHardwareaddresslenProtocoladdresslenOperationRequest1,Reply2Senderhardwareaddress（Forexample，6bytesforEthernet）Senderprotocoladdress（Forexample，4bytesforIP）Targethardwareaddress（Forexample，6bytesforEthernet）Targetprotocoladdress（Forexample，4bytesforIP）Itisnotfilledinarequest2022/10/29TCP/IPProtocolSuite12EncapsulationofARPpacketThebyteorderofARPpacketExample：EthernetframeHTypePTypeHLPLOPsMACsIPtMACtIP222116644byteARPPacket目的MAC類型FCS源MACPacket66246~15004pad28bytes460x0806byte2022/10/29TCP/IPProtocolSuite13Example:ARPRequestPacket2022/10/29TCP/IPProtocolSuite14Example:ARPReplyPacket2022/10/29TCP/IPProtocolSuite15IPPacketandARPPacketIPIPIPIPARPrequestARPreplyIPpacketBindingIPpacketIPpacketIPpacketNobinding2022/10/29TCP/IPProtocolSuite16ARPProcessCase1：ABInsameIPnetworkCase2：ADIndifferentIPnetworkACBDR1R2IPA，MACAIPB，MACBIPC，MACCIPD，MACDIP1MAC1IP2MAC2IP3MAC3IP4MAC42022/10/29TCP/IPProtocolSuite17Case1：ABACBDR1R2IPA，MACAIPB，MACBIPC，MACCIPD，MACDIP1MAC1IP2MAC2IP3MAC3IP4MAC4IPAddressMACAddressA’sARPCache：IPBMACBB’sARPCache：IPAMACAR1’sARPCache：IPAMACAsIP=IPA，dIP=IPBARPrequestARPrequestARPrequestARPrequestARPreplyIPIPsMAC=MACA，dMAC=MACBsIP=IPA，dIP=IPBdMAC=廣播，Target_IP=IPBSenderhardwareaddress:MACASenderprotocoladdress:IPATargethardwareaddress:

0x00000000Targetprotocoladdress:IPBSenderhardwareaddress:MACBSenderprotocoladdress:IPBTargethardwareaddress:

MACATargetprotocoladdress:IPA2022/10/29TCP/IPProtocolSuite18Case2：ADACBDR1R2IPA，MACAIPB，MACBIPC，MACCIPD，MACDIP1MAC1IP2MAC2IP3MAC3IP4MAC4IPAddressMACAddressA’sARPCache：IP1MAC1B’sARPCache：IPAMACAR1’sARPCache：IPAMACAsIP=IPA，dIP=IPDARPrequestARPrequestARPrequestARPrequestARPreplyIPIPsMAC=MACA，dMAC=MAC1sIP=IPA，dIP=IPDdMAC=廣播，Target_IP=IP1IPD不在本網(wǎng)內(nèi)，分組由R1轉發(fā)sMAC=MAC2，dMAC=MAC3sIP=IPA，dIP=IPDsMAC=MAC4，dMAC=MACDsIP=IPA，dIP=IPDIP1是A的缺省網(wǎng)關（DefaultGateway）2022/10/29TCP/IPProtocolSuite19關鍵問題：ARP解析誰的IP地址？交付類型2022/10/29TCP/IPProtocolSuite20ExampleAhostwithIPaddress0andphysicaladdress0xB23455102210hasapackettosendtoanotherhostwithIPaddress5andphysicaladdress0xA46EF45983AB.ThetwohostsareonthesameEthernetnetwork.ShowtheARPrequestandreplypacketsencapsulatedinEthernetframes.2022/10/29TCP/IPProtocolSuite21Example:ARPRequest2022/10/29TCP/IPProtocolSuite22Example:ARPReply12022/10/29TCP/IPProtocolSuite23ProxyARP（代理ARP）ProxyARP:——產(chǎn)生子網(wǎng)效應代表另一個物理網(wǎng)絡中一組主機回答ARPRequest，在ARPReply中通告自己的MAC地址（即將解析的IP與代理ARP的MAC綁定）TofoolthesenderoftheARPrequestintothinkingthattherouteristhedestinationhost,wheninfactthedestinationhostis"ontheotherside"oftherouter“Honest”HidedQ:InthesameIPnetworkornot?子網(wǎng)效應：屬于相同IP子網(wǎng)的節(jié)點間通信仍然需要經(jīng)過路由器轉發(fā)2022/10/29TCP/IPProtocolSuite24AnswerRFC925:Multi-LANAddressResolutionExplicitsubnetsTransparentsubnets（ExtendedARP）RFC1027:UsingARPtoImplementTransparentSubnetGatewaysRouters:ExplicitsubnetsHosts:Transparentsubnets“Fromthehostpointofview,therearenosubnets,andtheirphysicalnetworksaresimplyonebigIPnetwork.”2022/10/29TCP/IPProtocolSuite25ProxyARP功能Tobeusedtocreateasubnettingeffect

兩個物理網(wǎng)絡，具有相同網(wǎng)絡地址（即不需要重新劃分子網(wǎng)）使用路由器分別連接這兩個網(wǎng)絡，并執(zhí)行ARP代理，實現(xiàn)兩個邏輯子網(wǎng)方案：路由器上運行ProxyARP軟件 transparentsubnetgateway當路由收到對特定主機的ARP請求時，用自己的物理地址（接收端口）進行ARP應答代理ARP應答的條件（同時滿足）：與源站點不在同一邏輯子網(wǎng)的主機路由器有到達該節(jié)點的路由（非默認路由）且路由表項記錄的發(fā)送接口≠接收該ARP請求的接口2022/10/29TCP/IPProtocolSuite26Discussion.3向.35發(fā)送IP分組.3廣播請求.35的ARP分組，R不轉發(fā)廣播.35向.3發(fā)送IP分組.35廣播請求.62的ARP分組R/24Mainnetwork2/27Hidednetwork.00.201IP發(fā)送失敗IP發(fā)送成功ARP失敗ARP成功設想：R代替.35向.3返回ARP應答——ProxyARP（RFC925）2022/10/29TCP/IPProtocolSuite27GratuitousARP功能：DuplicateaddresstestAB441.ARPrequest:

sIP=tIP=42.ARPreply:sIP=tIP=43.Disablelocalinterface:4StartuporChangeIPaddressW.Stevens,TCP/IPIllustratedVolume1:TheProtocol2022/10/29TCP/IPProtocolSuite28GratuitousARPPacketThesamesenderandtargetIPaddress2022/10/29TCP/IPProtocolSuite29Chapter6ARPandRARPARPARPpackage（ARP軟件包）RARP2022/10/29TCP/IPProtocolSuite30ARPPackage2022/10/29TCP/IPProtocolSuite31ARPCacheHost（WindowsXP）Router（Cisco）C:\>arp–aInterface:4---0x2InternetAddress PhysicalAddress Type3 00-90-27-a7-98-41 dynamic7 00-90-27-1d-d9-94 dynamic2 00-90-27-1a-67-e7 dynamicRouter#showarpProtocolAddressAge(min)HardwareAddrTypeInterfaceInternet 3 -- 0090.27a7.9841ARPAEthernet0Internet 4 5 0005.5d06.1418ARPAEthernet0Internet -- 00e0.7bc0.b205ARPAEthernet12022/10/29TCP/IPProtocolSuite32思考更新ARP綁定時，發(fā)現(xiàn)已有的綁定與新的綁定不一樣，是保持已有的還是替換它？封裝IP報文的以太幀中的源MAC和IP報文中的源IP可否用于刷新ARP表項？目的MAC和目的IP呢？2022/10/29TCP/IPProtocolSuite33RFCReferencesRFC1122:RequirementsforInternetHosts--CommunicationLayersSection2.3.2:ARPcache,ARPpacketqueueRFC1812:RequirementsforIPv4RoutersSection3.3.2RFC1433:DirectedARPARPhelperaddressRF