开放链路最短优先OpenShortestPathFirst.ppt

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1、开放链路最短优先Open Shortest Path First,深圳职业技术学院计算机系网络专业,链路状态协议（Link-State Protocols）,OSPF概述（OSPF Overview）,分层设计（Hierarchical Design）,1.大的OSPF网络采用分层设计，所有区域连接到主干区域。Large OSPF networks use a hierarchical design.Multiple areas connect to a distribution area,area 0,also called the backbone.2.好处（benefit）：（1）减少路

2、由更新（reduces routing overhead）（2）加速收敛（speeds up convergence）（3）限制不稳定到一个区域（confines network instability to an area）（4）提高网络性能（improves performance）,OSPF术语（OSPF Terminology）,OSPF数据包类型（OSPF Packet Types）,OSPF数据包头格式（OSPF Packet Header Format）,OSPF操作（OSPF Operation）,1.建立邻接关系Establish router adjacencies2.必要

3、的进行DR选举Elect the DR/BDR(if necessary)3.发现路由Discover routes4.选择相应的路由Select appropriate routes5.维护路由信息Maintain routing information,邻居关系（Neighborship）,*标记的在邻居路由器上必须匹配,建立双向通信（Establishing Bidirectional Communication）,建立双向通信（Establishing Bidirectional Communication）,建立双向通信（Establishing Bidirectional Comm

4、unication）,建立双向通信（Establishing Bidirectional Communication）,查找网络路由（Discovering the Network Routes）,查找网络路由（Discovering the Network Routes）,增加链路状态条目（Adding the Link-State Entries）,增加链路状态条目（Adding the Link-State Entries）,增加链路状态条目（Adding the Link-State Entries）,维护路由信息（Maintaining Routing Information）,路由

5、器用224.0.0.6通知DR Router A notifies all OSPF DRs on 224.0.0.6,维护路由信息（Maintaining Routing Information）,DR利用组播地址224.0.0.5通知其它路由器DR notifies others on 224.0.0.5,维护路由信息（Maintaining Routing Information）,维护路由信息（Maintaining Routing Information）,维护路由信息（Maintaining Routing Information）,OSPF网络类型（OSPF Network Ty

6、pes）,Frame RelayX.25,广播Broadcast Multiaccess,非广播Nonbroadcast Multiaccess,点到点Point-to-Point,点到多点Point-to-Multipoint,点到点链路（Point-to-Point Links）,1.不进行DR选举No DR or BDR election required2.OSPF自动检测这种接口类型 OSPF autodetects this interface type,广播型多路访问网络（Multiaccess Broadcast Network）,1.进行DR选举 DR and BDR sel

7、ection required 2.邻居只与DR和DBR形成邻接关系All neighbor routers form full adjacencies with the DR and BDR only,选举DR和BDR（Electing the DR and BDR）,1.最高接口优先级的路由器被选成DR The router with the highest OSPF priority is selected as the DR.2.最高路由器ID的路由器被选举成DR Use the OSPF router ID as the tie breaker.3.DR选举不具有抢占性The DR

8、election is nonpreemptive.,设置接口优先级（Setting Interface Priority）,ip ospf priority number,1.不同的接口可以指定不同的值Different interfaces on a router may be assigned different values.2.接口优先级默认为1,取值范围是0-255The default priority is 1.The range is from 0 to 255.3.接口优先级为0表示不参加DR选举0 means the router is a DROTHER;it cant

9、 be the DR or BDR.,Router(config-if)#,router ospf process-id,Router(config)#,启动路由进程Turns on one or more OSPF routing processes,OSPF基本配置（Configuring Basic OSPF）,network address inverse-mask area area-id,Router(config-router)#,用network命令ospf运行的接口，并将网络指定到特定的区域Router OSPF subordinate command that define

10、s the interfaces(by network number)that OSPF will run on.Each network number must be defined to a specific area.,OSPF配置实例（Configuring OSPF Example）,验证ospf配置（Verifying OSPF Operation）,show ip protocolsShow ip ospf neighborShow ip ospf databaseShow ip routeShow ip ospfShow ip ospf interfaceDebug ip os

11、pf adjDebug ip ospf event,确定OSPF路由器ID（OSPF Router ID）,1.通过router-id命令指定的最为优先An OSPF router-id command can override OSPF router ID.2.最高的环回接口地址次之A loopback interface can override OSPF router ID.It is the highest IP address of any active loopback interface.3.最后是最高活动的物理接口的IP地址the router ID is the highes

12、t IP address on an active interface at the moment of OSPF process startup.为了稳定，命令或环回接口被推荐The loopback or router-id command is recommended for stability.,环回接口（Loopback Interfaces）,interface loopback 0,ip address 172.16.17.5 255.255.255.255,如果ospf路由进程已经启动，必须重新清除ospf进程，新的路由器ID才生效。If the OSPF process is

13、 already running,the OSPF process must be cleared before the new router-id command will take effect.,Router(config)#,Router(config-if)#,router-id ip-address,这是路由进程下的子命令This command is subordinate to the router-id ospf command.用clear ip ospf process 命令可以使得配置生效。If this command is used on an OSPF proce

14、ss that is already active,then the new router ID is used at the next reload or at a manual OSPF process restart using the clear ip ospf process command.,OSPF router-id 命令（OSPF router-id command）,router ospf 1,router-id 172.16.1.1,Router(config-router)#,Router(config-if)#,Router(config-router)#,显示路由器

15、ID（OSPF Router ID Verification）,RouterA#show ip ospf Routing Process ospf 1 with ID 1.1.3.1 Supports only single TOS(TOS0)routes SPF schedule delay 5 secs,Hold time between two SPFs 10 secs Number of DCbitless external LSA 0 Number of DoNotAge external LSA 0 Number of areas in this router is 1.1 nor

16、mal 0 stub 0 nssa Area BACKBONE(0)(Active)Number of interfaces in this area is 2 Area has no authentication SPF algorithm executed 10 times Area ranges are Link State Update Interval is 00:30:00 and due in 0:07:16 Link State Age Interval is 00:20:00 and due in 00:07:15 Number of DCbitless LSA 0 Numb

17、er of indication LSA 0 Number of DoNotAge LSA 0,配置OSPF计时器（Configuring OSPF Timers）,OSPF计时器在接口下配置,配置OSPF认证（Configuring OSPF Authentication）,维护大的OSPF网络的问题（Issues with Maintaining a Large OSPF Network）,解决方案：OSPF分层路由（The Solution:OSPF Hierarchical Routing）,OSPF路由器类型（Types of OSPF Routers）,OSPF路由器类型（Type

18、s of OSPF Routers）,OSPF路由器类型（Types of OSPF Routers）,OSPF路由器类型（Types of OSPF Routers）,OSPF路由器类型（Types of OSPF Routers）,OSPF路由的类型（Types of Routes）,E1和E2路由 cost计算（Calculating Costs for E1 and E2 Routes）,E1和E2路由 cost计算（Calculating Costs for E1 and E2 Routes）,area area-id range address mask,Router(config

19、-router)#,Consolidates inter-area(IA)routes on an ABR,配置路由汇总（Configuring Route Summarization）,summary-address address mask not-advertise tag tag,Router(config-router)#,Consolidates external routes,usually on an ASBR,在ABR配置路由汇总实例（Route Summarization Configuration Example at ABR）,在ASBR配置路由汇总实例（Route S

20、ummarization Configuration Example at ABSR）,RIPv2必须重分布进OSPFRIPv2 must be redistributed into OSPF,OSPF中默认路由（Default Routes in OSPF）,default-information originate always,Router(config-router)#,默认路由配置实例（Default Route Configuration Example）,Case Study,思考题（Questions）,1.OSPF是一种典型的_路由协议。2.OSPF路由协议的管理距离是_。3

21、.OSPF路由协议采用_作为度量标准。4.OSPF路由器利用_算法，独立地计算出到达任意目的地的路由。5.默认情况下，快速以太网的开销是_。6.OSPF将网络划分为四种类型：_、_、_、_。7.Ethernet的Hello Interval为_秒，Dead Interval为_秒。8.NBMA网络的Hello Interval_秒，Dead Interval为_秒。9.OSPF路由器可以周期性发送_包来建立和维持邻居关系。10.当DR和BDR需要发送一个LSU时，它会将更新发送给组播地址_。11.OSPF接口优先级的范围是_。12.OSPF路由进程process-id必须指定范围在_。13.当络区域ID为_的区域称为主干区域。14._ 命令用来查看邻居及其状态。15.OSPF通过_两种方法启用认证功能。16.OSPF路由器的类型为_、_、_、_。17.OSPF区域类型包括_、_、_、_。18._区域负责把LSA Type 7转换成LSA Type 5。19.OSPF路由汇总的两种类型包括_。20.如何确定Router ID？21.OSPF的特性包括哪些？,