ccna中文课件16.广域网技术

WAN连接了解WAN技术IntroducingWANsWhatisaWAN?IntroducingWANs(Cont.)WhyareWANsneeded?WANsvs.LANsWAN=AcollectionofLANsWANsvs.LANs(Cont.)

WANDevicesRoutersCSU/DSUWANswitchesCoreroutersModemsWANDevices(Cont.)

RoleofRoutersinWANsWANsvs.LANsSerialWANCabling

WANLayer2Protocols

WANLinkOptionsWANLinkOptions(Cont.)Point-to-PointConnectivityEthernetemulation:简单价格适中灵活SerialCommunicationLinksSeriallinksuseleasedlinestoprovideadedicatedconnection.SerialCommunicationLinksThesearethetypicalWANspeedsfortheUnitedStates:T1(1.544Mb/s)T2=4T1lines(6Mb/s)T3=28T1lines(45Mb/s)T4=168T1lines(275Mb/s)ThesearethetypicalWANspeedsforEurope:E1(2Mb/s)E2=128E0lines(8Mb/s)E3=16E1lines(34Mb/s)E4=64E1lines(140Mb/s)HDLC和CiscoHDLCHDLCspecifiesanencapsulationmethodfordataonsynchronousserialdatalinks.RouterX(config-if)#encapsulationhdlc启用CiscoHDLC封装在同步串行接口上使用默认封装配置HDLC封装Point-to-PointProtocolOverviewofPPP:PPPprovidesastandardmethodfortransportingdatagramsoverpoint-to-pointlinks.PPPsupportsauthentication.Point-to-PointProtocol(Cont.)PPPisalayeredarchitecture:PPPcancarrypacketsfromseveralprotocolsuitesusingNCP.PPPcontrolsthesetupofseverallinkoptionsusingLCP.PPPConfigurationPPPconfigurationonRouterAPPPConfiguration(Cont.)PPPconfigurationonRouterBPPPConfiguration(Cont.)

PPPAuthentication:PAPPasswordAuthenticationProtocol:Passwordaresentinplaintext.Thepeerisincontrolofattempts.PPPAuthentication:CHAPChallengeHandshakeAuthenticationProtocol:Hashvalues,notactualpasswords,aresentacrossthelink.Thelocalrouterorexternalserverisincontrolofauthenticationattempts.ConfiguringCHAPforPPPAuthentication

配置PPP和身份验证RouterX(config-if)#encapsulationppp启用PPP封装RouterX(config)#hostnamename给路由器指定主机名RouterX(config)#usernamenamepasswordpassword标识远程路由器的用户名和口令RouterX(config-if)#pppauthentication

{chap|chappap|papchap|pap}启用PAP或CHAP身份验证ConfiguringCHAPforPPPAuthentication(Cont.)ConfiguringCHAPauthenticationonRouterA.ConfiguringCHAPforPPPAuthentication(Cont.)ConfiguringCHAPauthenticationonRouterB.VerifyingCHAPConfigurationThedebugpppauthenticationcommandsshowsthesuccessfulCHAPoutputandverifiesPPPauthentication.总结PPP是适用于WAN的常用第2层协议。PPP包括两个组件：协商连接的LCP和封装流量的NCP。可将PPP配置为使用PAP或CHAP。PAP以明文形式发送所有信息。CHAP使用MD5哈希。常用PPP验证命令包括用于检验PPP封装的showinterface

命令，以及用于检验LCP握手的debugpppnegotiation

命令。WAN有三大特点：连接分布于相距甚远的不同地域的设备；使用运营