IP路由高级技术(二)

2020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations1IP路由协议（二）NE实验室，2008西安邮电学院快速convergence支持VLSM更新处理效率高基于带宽选择路由支持等值的多路由OSPF主要特点2020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations3IP分组中OSPF的标识•OSPF是一个链路状态协议–依靠IP分组传送链路状态信息–协议号是89IPHeaderProtocolNumberFrameHeaderCRCPacketPayloadFramePayload89-OSPF6-TCP17-UDPOSPF术语TokenRingInterfacesOSPF术语NeighborsTokenRingInterfaces2020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations6NeighborsTokenRingInterfacesOSPF术语Cost=10Cost=6Cost=1785OSPF术语NeighborsTokenRingInterfacesArea1Area0Cost=10Cost=6Cost=17852020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations8OSPF术语AutonomousSystemNeighborsTokenRingInterfacesArea1Area0Cost=1785Cost=10Cost=6AutonomousSystemOSPF术语NeighborshipDatabase列出所有的邻居NeighborsTokenRingInterfacesArea1Area0Cost=10Cost=6Cost=1785AutonomousSystemOSPF术语TopologyDatabase列出所有的路由NeighborshipDatabase列出所有的邻居NeighborsTokenRingInterfacesArea1Area0Cost=1785Cost=10Cost=6AutonomousSystemOSPF术语RoutingTable列出最佳路由TopologyDatabase列出所有的路由NeighborshipDatabase列出所有的邻居Cost=10Cost=1785Cost=6NeighborsTokenRingInterfacesArea1Area0©2000,CiscoSystems,Inc.支持的网络类型Point-to-PointNBMABroadcastMultiaccessX.25FrameRelay©2000,CiscoSystems,Inc.*****必须与邻居路由器保持一致的参数项HelloADECBDR和BDRDRBDR通过Hello报文的交互选举一个网段的DR、BDR每个路由器然后建立和DR、BDR的邻接关系Hello分组通过IPmulticast的方式在路由器间交换具有最高OSPF优先级的路由器将被选举为DRP=1P=0P=1选举DR和BDRP=3P=2DRBDRHello交换过程172.16.5.1/24E0172.16.5.2/24E1ABDownState交换过程172.16.5.1/24E0172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateAB交换过程172.16.5.1/24E0IamrouterID172.16.5.2,andIsee172.16.5.1.172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateAB交换过程172.16.5.1/24E0IamrouterID172.16.5.2,andIsee172.16.5.1.RouterANeighborsList172.16.5.2/24,intE0172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateTwo-WayStateAB发现路由E0172.16.5.1DRE0172.16.5.3No,IwillstartexchangebecauseIhaveahigherrouterID.IwillstartexchangebecauseIhaverouterID172.16.5.1.Helloafadjfjorqpoeru39547439070713Helloafadjfjorqpoeru39547439070713ExstartState发现路由Hereisasummaryofmylink-statedatabase.DBDafadjfjorqpoeru39547439070713ExchangeStateHereisasummaryofmylink-statedatabase.DBDafadjfjorqpoeru39547439070713E0172.16.5.1DRE0172.16.5.3No,IwillstartexchangebecauseIhaveahigherrouterID.IwillstartexchangebecauseIhaverouterID172.16.5.1.Helloafadjfjorqpoeru39547439070713Helloafadjfjorqpoeru39547439070713ExstartState发现路由(cont.)E0172.16.5.1E0172.16.5.3Thanksfortheinformation!LSAckafadjfjorqpoeru39547439070713LSAckafadjfjorqpoeru39547439070713DR发现路由(cont.)Ineedthecompleteentryfornetwork172.16.6.0/24.Hereistheentryfornetwork172.16.6.0/24.Thanksfortheinformation!LSRafadjfjorqpoeru39547439070713LSAckafadjfjorqpoeru39547439070713LSUafadjfjorqpoeru39547439070713LoadingStateE0172.16.5.1E0172.16.5.3Thanksfortheinformation!LSAckafadjfjorqpoeru39547439070713LSAckafadjfjorqpoeru39547439070713DR发现路由(cont.)FullStateIneedthecompleteentryfornetwork172.16.6.0/24.Hereistheentryfornetwork172.16.6.0/24.Thanksfortheinformation!LSRafadjfjorqpoeru39547439070713LSAckafadjfjorqpoeru39547439070713LSUafadjfjorqpoeru39547439070713LoadingStateE0172.16.5.1E0172.16.5.3Thanksfortheinformation!LSAckafadjfjorqpoeru39547439070713LSAckafadjfjorqpoeru39547439070713DR选择路由TopologyTableNetCostOutInterface10.2.2.06To010.3.3.07To010.3.3.010E0TokenRingCost=10Cost=6FDDICost=1ABCThisisthebestrouteto10.3.3.0.10.1.1.0/2410.2.2.0/2410.3.3.0/2410.4.4.0/24维护路由信息•路由器A通过224.0.0.6告诉所有的OSPFDRsxx链路状态改变LSU1DRAB维护路由信息LSU2•路由器A通过224.0.0.6告诉所有的OSPFDRs•DR通过224.0.0.5告诉其它路由器xx链路状态改变LSU1DRABLSU3维护路由信息LSU2xx链路状态改变LSU1DRAB•路由器A通过224.0.0.6告诉所有的OSPFDRs•DR通过224.0.0.5告诉其它路由器维护路由信息Ineedtoupdatemyroutingtable.4LSU3LSU2xx链路状态改变LSU1DRAB•路由器A通过224.0.0.6告诉所有的OSPFDRs•DR通过224.0.0.5告诉其它路由器维护路由信息(cont.)该项是否已在link-statedatabase?中LSALSUNo执行SPF计算新的路由表加入database中洪泛LSAEnd发送LSAck给DR维护路由信息(cont.)YesIsseq.#thesame?Yes忽略LSA该项是否已在link-statedatabase?中LSALSUNo执行SPF计算新的路由表加入database中洪泛LSAEnd发送LSAck给DRA维护路由信息(cont.)No发送带有最新路由信息LSU给源Isseq.#higher?NoYesIsseq.#thesame?Yes忽略LSAEnd该项是否已在link-statedatabase?中LSALSUNo执行SPF计算新的路由表加入database中洪泛LSAEnd发送LSAck给DRA维护路由信息(cont.)Yes转到ANo发送带有最新路由信息LSU给源Isseq.#higher?NoYesIsseq.#thesame?Yes忽略LSAEnd该项是否已在link-statedatabase?中LSALSUNo执行SPF计算新的路由表加入database中洪泛LSAEnd发送LSAck给DRA2020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations36在点对点拓扑上的OSPFOperation©2000,CiscoSystems,Inc.邻居关系Router使用Hello协议动态检测它的邻居没有选举过程:两个路由器已通信，邻接关系自动形成OSPF分组总是通过224.0.0.5(多播地址)发送2020/4/19YangWu-Jun,xi'anInstituteofPostandTelecommuniations38NBMA拓扑的OSPFOperation