第5章-IP路由基础

1、第5章 IP路由基础 本章主要讲述IP路由的工作过程、路由表的作用以及路由分类和路由环路的产生与预防技术要求掌握内容： 路由表内容的查看及各条目的含义； 设置静态路由； 距离向量和链路状态路由协议的工作原理与特点。 章节内容5.1 IP路由基础5.2 静态路由与动态路由5.3 路由环路预防技术5.4 实验5.5 小结5.1 IP路由什么是IP路由IP路由表什么是IP路由路由器需要知道以下信息才能进行路由:目标地址如何获得路由信息可能的路由最好的路由如何保存与验证路由信息192.168.0.1R1R2R3R4网络协议目标网络ConnectedLearned10.120.2.0172.16.1.0

2、出口E0S0路由器必须学习没有直接相连的网络的信息R1什么是IP路由R2R3R4IP路由表ABCE0S0S0E0E0E1Routing TableRouting Table10. 0 2.010. 0. 3.010. 0. 4. 010. 0. 1. 00011S0S1E0S0Routing Table10. 0 3.0E0010. 0 4.0E1010. 0 2.0E0 E0 12E0S0S0120010. 0. 4. 0S0IP路由表的内容RouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M

3、- mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static r

4、oute, o - ODR, P - periodic downloaded static route T - traffic engineered routeGateway of last resort is not set 10.0.0.0/24 is subnetted, 4 subnetsC 10.0.2.0 is directly connected, Serial0C 10.0.3.0 is directly connected, Ethernet0R 10.0.1.0 120/1 via 10.0.2.1, Serial0R 10.0.4.0 120/1 via 10.0.3.2

5、, Ethernet0主机路由表内容C:route printIPv4 Route Table=Interface List0 x1 . MS TCP Loopback interface0 x10003 .00 0a eb a2 02 88 . TP-LINK 11G Wireless Adapter0 x10004 .00 e0 18 55 55 7d . HP NetServer 10/100TX PCI LAN Adapter=Active Routes:Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0

6、.0 100.100.109.254 100.100.109.252 30 100.100.109.0 255.255.255.0 100.100.109.252 100.100.109.252 30 100.100.109.252 255.255.255.255 127.0.0.1 127.0.0.1 30 100.255.255.255 255.255.255.255 100.100.109.252 100.100.109.252 30 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 224.0.0.0 240.0.0.0 100.100.109.252

7、 100.100.109.252 30 255.255.255.255 255.255.255.255 100.100.109.252 100.100.109.252 1=5.2 静态路由与动态路由静态路由配置静态路由（含默认路由）动态路由基础内部网关协议与外部网关协议管理距离路由选择的分类静态与动态路由静态路由管理管理员手工输入到路由表中动态路由使用路由协议根据网络的拓扑和流量变化动态学习获得SO静态路由BNetworkAB承接网络（Stub Network）配置静态路由定义一个到IP目标网络或子网的路径Router(config)#ip route network mask address

8、 | interfacedistance permanent Stub NetworkSO静态路由举例BNetworkABStub Network默认路由SOBNetworkAB动态路由基础-路由协议路由协议用来在路由器之间选择路径和保存路由表。网络协议目标网络ConnectedRIPIGRP出口E0S0S1路由协议: RIP, IGRPE0S0路由协议量化参数 结点数（hop count）带宽（bandwidth）负载（load）延迟（delay）可靠性（reliability）代价（cost）最大传输单元MTU（maximum transmission unit） 量化参数（ Metric

9、s）应用56T156T1Ticks, hop countBAHop countIPXRIPIGRPBandwidthDelayLoadReliabilityMTU查看量化参数RouterB#show int e0Ethernet0 is up, line protocol is up Hardware is Lance, address is 0060.5cf3.e6b6 (bia 0060.5cf3.e6b6) Description: this port is linked to mainoffice. MTU 1500 bytes, BW 10000 Kbit, DLY 1000 use

10、c, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00动态路由协议的配置定义一个IP路上协议Router(config)#router protocol keyword 指定运行路由协议的网络Router(config-router)#network network-numberAutonomous System 100Autonomous System 2

11、00IGPs: RIP, IGRPEGPs: BGP自治系统：内部与外部路由协议自治系统指一个具有统一管理机构、统一路由策略的网络 IGPs 操作在自治系统内部EGPs 连接不同的自治系统管理距离-路由协议的路由可信度 IGRPAdministrative Distance=100Router DRouter BRouter ARouter CRIPAdministrative Distance=120E我需要将一个包发送到网络E，通过路由器B与C都可以到达，那么，哪一个路径最好呢？常用协议的管理距离路由源默认值直接相连的端口0静态路由1EIGRP90IGRP100OSPF110RIP120外

12、部EIGRP170未知/不可信的 255（不可用）路由协议的分类Distance VectorHybrid RoutingLink StateCBADCDBA距离向量协议周期性地将路由表复制邻居路由器，累计计算距离向量CDBACBADRoutingTableRoutingTableRoutingTableRoutingTableDistanceHow farVectorIn which directionABCE0S0S0S1S0E0Routing Table 00S0S1Routing TableS00E00Routing Table E0S0 00路由表的形成过程-初使状态 ABCE0S0

13、S0S1S0E0Routing TableRouting Table0011S0S1S1S0Routing TableS00E00S0 1E0S0S0100路由表的形成过程-首次交换后 路由表的形成过程-收敛状态 ABCE0S0S0S1S0E0Routing TableRouting Table0011S0S1S1S0Routing TableS00E00S0S012E0S0S0S01200链路状态路由协议初使泛洪后，基于事件触发更新的机制传递变化信息Link-State PacketsSPFAlgorithmTopologicalDatabaseShortest Path First Tre

14、eRoutingTableCADB混合路由协议兼有距离向量和链路状态路由协议的特点基于距离向量选择路径基于变化的更新机制混合路由协议5.3 路由环路预防技术路由环路的产生设置最大度量值反向抑制（Split Horizon）技术保持计时技术触发更新路由环路的产生（一）会聚状态ABCE0S0S0S1S0E0Routing TableS0E0S0S01200Routing TableE0S0S0S01200Routing TableS0S1S1S01100路由环路的产生（二）慢速汇聚产生了路上不一致ABCE0S0S0S1S0E0XRouting TableS0E0S0S0120DownRouting

15、 TableE0S0S0S01200Routing TableS0S1S1S01100路由器C认为到达网络通过路由器路由环路的产生（三）ABCE0S0S0S1S0E0XRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.002Routing Table10.1.0.0E0S0S0S01210.4.0.010.3.0.010.2.0.000Routing Table10.2.0.0S0S1S1S11110.1.0.010.4.0.010.3.0.000路由器A更新自己的路由表来反映新的变化，但实际上是错误的跳计数路由环路的产生（四）ABCE

16、0S0S0S1S0E0XRouting TableS0S0S0S01210.3.0.010.1.0.010.2.0.010.4.0.002Routing TableE0S0S0S01410.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1S03110.2.0.010.1.0.010.4.0.010.3.0.000路由环路的产生（五）信息包在三个路由器间来回传递网络跳计数一直计数到无穷ABCE0S0S0S1S0E0XRouting TableS0S0S0S01204Routing TableE0S0S0S01610.1.0.010.4.0.01

17、0.3.0.010.2.0.000Routing TableS0S1S1S05110.2.0.010.1.0.010.4.0.010.3.0.000解决方法（ 一）：定义最大值定义一个最大值防止无限的循环计数ABCE0S0S0S1S0E0XRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.0016Routing TableE0S0S0S011610.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1S016110.2.0.010.1.0.010.4.0.010.3.0.000解决方法（

18、二）：反向抑制（Split Horizon）技术 不反向通告任何从源端收到的路由更新信息 ABCE0S0S0S1S0E0XXXRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.000Routing TableE0S0S0S01210.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1E11210.2.0.010.1.0.010.4.0.010.3.0.000解决方法（三）：保持计时技术 （ Hold-Down Timers）路由器在某个时间段内拒绝任何可能会影响路由改变的信息 Network 10.4.0.0 is downthen back up then back downUpdate afterhold-down Timeis unreachableABCE0S0S0