单区域OSPF协议及SPF算法(ppt 21页).ppt

路由原理,第二课单区域OSPF协议及SPF算法,课程目标,通过本课的学习，让学生掌握OSPF的特性，OSPF单区域基本配置，并了解spf算法的特点,本课内容,1.1：单区域OSPF协议的配置以及工作机制1.2：什么是最短路径优先算法（SPF）,OSPF单区域配置,routerospfprocess-idvrfvpn-name,Router(config)#,开启OSPF路由进程,OSPF基本配置,networkip-addresswildcard-maskareaarea-id,Router(config-router)#,定义OSPF将运行在哪个接口,Router(config-if)#,ipospfprocess-idareaarea-idsecondariesnone,在指定的接口启用OSPF,单区域实验要求,任务：OSPF单区域的配置配置loopback地址作为路由器的ID配置OSPF的进程并在相应的接口上启用完成标准可以ping通各路由器的loopback地址showrun时可以查看到每台路由器所属的区域,OSPFRouterID,运行OSPF的路由器之间是通过OSPF的routerID来相互识别的LSDBs使用OSPFrouterID来区分路由器默认，OSPF的routerID是使用被激活的接口的最高的ip地址如果有loopbackinterface那么它将成为OSPFrouterID如果有多个loopbackinterface那么将选择其中ip地址最大的可以使用命令配置指定的OSPFrouter-id,Router(config)#interfaceloopback0Router(config-if)#ipaddress172.16.17.5255.255.255.255,如果OSPF的进程已经运行的时候，想更改RouterID则必须要重新启动OSPF的进程，才能使新的RouterID生效,LoopbackInterfaces,router-idip-address,配置OSPFrouter-id命令,Router(config-router)#,Router(config)#routerospf1Router(config-router)#router-id172.16.1.1Router#clearipospfprocess,clearipospfprocess,Router#,OSPFRouterID验证,RouterB#shipospfRoutingProcessospf50withID10.64.0.2Numberofareasinthisrouteris2.2normal0stub0nssaNumberofareastransitcapableis0Externalfloodlistlength0AreaBACKBONE(0)AreaBACKBONE(0)AreahasnoauthenticationSPFalgorithmlastexecuted00:01:25.028agoSPFalgorithmexecuted7timesArea1Numberofinterfacesinthisareais1AreahasnoauthenticationSPFalgorithmlastexecuted00:00:54.636agoSPFalgorithmexecuted3times,showipprotocols,Router#,OSPF的检验,showiprouteospfprocess-id,Router#,showipospfinterfacetypenumber,Router#,showipospf,Router#,OSPF的检验,showipospfneighbortypenumberneighbor-iddetail,Router#,例：showiprouteospf,RouterA#showiprouteospf10.0.0.0/8isvariablysubnetted,3subnets,2masksOIA10.2.1.0/24110/782via10.64.0.2,00:03:05,FastEthernet0/0RouterA#,例：showipospfinterface,RouterA#showipospfinterfacefastEthernet0/0FastEthernet0/0isup,lineprotocolisupInternetAddress10.64.0.1/24,Area0ProcessID1,RouterID10.64.0.1,NetworkTypeBROADCAST,Cost:1TransmitDelayis1sec,StateDROTHER,Priority0DesignatedRouter(ID)10.64.0.2,Interfaceaddress10.64.0.2NobackupdesignatedrouteronthisnetworkTimerintervalsconfigured,Hello10,Dead40,Wait40,Retransmit5oob-resynctimeout40Helloduein00:00:04SupportsLink-localSignaling(LLS)Index1/1,floodqueuelength0Next0 x0(0)/0 x0(0)Lastfloodscanlengthis1,maximumis4Lastfloodscantimeis0msec,maximumis4msecNeighborCountis1,Adjacentneighborcountis1Adjacentwithneighbor10.64.0.2(DesignatedRouter)Suppresshellofor0neighbor(s),例:Theshowipospfneighbor,RouterB#showipospfneighborNeighborIDPriStateDeadTimeAddressInterface10.64.0.10FULL/DROTHER00:00:3010.64.0.1FastEthernet0/010.2.1.10FULL/-00:00:3410.2.1.1Serial0/0/1,RouterB#showipospfneighbordetailNeighbor10.64.0.1,interfaceaddress10.64.0.1Inthearea0viainterfaceFastEthernet0/0Neighborpriorityis0,StateisFULL,16statechangesDRis10.64.0.2BDRis0.0.0.0Neighbor10.2.1.1,interfaceaddress10.2.1.1Inthearea1viainterfaceSerial0/0/1Neighborpriorityis0,StateisFULL,6statechangesDRis0.0.0.0BDRis0.0.0.0,Dijkstra算法,Dijkstra算法是路由表计算的依据，通过Dijkstra算法可以得到有关网络节点的最短路径树，然后由最短路径优先树得到路由表。SPF算法有时也被称为Dijkstra算法，这是因为最短路径优先算法SPF是Dijkstra发明的。,Dijkstra算法,SPF算法将每一个路由器作为根（ROOT）来计算其到每一个目