路由环路次优路径详解.docx

1、路由环路次优路径详解1实验目的:解决路由环路路由环路存在的环境为，路由重分发且AD不一致的时候 。路由AD值高的路由 会出现路由环路。以下作出演示，并提出解决方案。实验需求:R1 R2 R3启用RIP V2路由协议，R1 R2 R4启用ospf。R1的回环口宣告进RIP，R2的回环口宣告进OSPF。R1Config tNo ip domain-lookupLine con 0Exec-timeout 0 0Logg synExitInt loop 0Ip add 1.1.1.1 255.255.255.0No shutInt s0/0Ip add 13.1.1.1 255.255.255.0N

2、o shutInt s0/1Ip add 14.1.1.1 255.255.255.0No shutExitRouter ospf 110Router-id 1.1.1.1Network 14.1.1.0 0.0.0.255 a 0ExitRouter rip Ver 2No auto-summaryNetwork 1.1.1.0Network 13.1.1.0ExitR2Config tNo ip domain-lookupLine con 0Exec-timeout 0 0Logg synExitInt loop 0Ip add 2.2.2.2 255.255.255.0No shutIn

3、t s0/0Ip add 24.1.1.2 255.255.255.0No shutInt s0/1Ip add 23.1.1.2 255.255.255.0No shutExitRouter ospf 110Router-id 2.2.2.2Network 24.1.1.0 0.0.0.255 a 0Network 2.2.2.0 0.0.0.255 a 0ExitRouter ripVer 2Network 23.1.1.0ExitR3Config tNo ip domain-lookupLine con 0Logg synExec-timeout 0 0ExitInt loop 0Ip

4、add 3.3.3.3 255.255.255.0No shutInt s0/1Ip add 23.1.1.3 255.255.255.0No shutInt s0/0Ip add 13.1.1.3 255.255.255.0No shutExitRouter ripVer 2Network 3.3.3.0Network 13.1.1.0Network 23.1.1.0ExitR4Config tNo ip domain-lookupLine con 0Logg synExec-timeout 0 0ExitInt loop 0Ip add 4.4.4.4 255.255.255.0No sh

5、utInt s0/0Ip add 24.1.1.4 255.255.255.0No shutInt s0/1Ip add 14.1.1.4 255.255.255.0No shutExitRouter ospf 110Router-id 4.4.4.4Network 14.1.1.0 0.0.0.255 a 0Network 24.1.1.0 0.0.0.255 a 0Network 4.4.4.0 0.0.0.255 a 0Exit在R1上 show ip route 查看 rip已经正常使用。接下来进行双点双向重分发。EIGRP 与IGP其他路由进行双向重分发的时候 不会出现路由环路，故我

6、们所使用的路由协议为rip &ospfR1Configt tRouter ospf 110Redistribute rip subnets (将rip重分布进入ospf 加上参数subnets)ExitRouter rip Ver 2Redistribute ospf 110 metric 2 (其他路由充分不进入rip时需注意要修改度量值，否则否认的度量值为15 不可达)ExitR2Config tRouter ospf 110Redistribute rip subnetsExitRouter rip Ver 2Redistribute ospf 110 metric 2Exit在R3上查

7、看是否收到了 重分发的路由。Show ip route rip出现很多次优路径，接下来在R2上面查看 有关3.3.3.3 这个路由。Rip里面含有3.3.3.3的这条路由，AD值为120OSPF里面也含有3.3.3.3 的这条路由，AD值为110综合以上，参照选路原则，则放进路由表的将会是AD值低的，即通往3.3.3.3 需经过R4 R1 R3 这样，行程路由回路，通往3.3.3.3的最佳路径本应是R2-R32解决次优路径的方案 ：R1：Config tRouter ospf 110Distance 121 2.2.2.2 0.0.0.255 (将从router-id为2.2.2.2 发出来的

8、ospf路由AD值修改为121)ExitR2Config tRouter ospf 110Distance 121 1.1.1.1 0.0.0.255(同理 从1.1.1.1发出来的ospf路由AD值改为121)接下来，在R2上使用show 查看到达3.3.3.3的下一条 是否已经变成23.1.1.3 OK，实验结束。3双点双向重发布控制2011-08-16 09:07:08 我来说两句 收藏 我要投稿 实验需求及应用环境：1在R5上执行双向重发布，再在R3上执行双向重发布2分析次佳路由产生的原因，及解决方案3.要求R4去往1.1.1.1能够负载均衡，如何实现？4.要求R4去往11.11.11

9、.11的下一跳首先R3,R5做备份，如何解决？实验调试过程：R1配置：router rip/配置RIPversion 2passive-interface defaultno passive-interface Ethernet0/0network 1.0.0.0network 11.0.0.0network 192.168.12.0no auto-summaryR2配置：router rip/配置RIPversion 2passive-interface defaultno passive-interface Ethernet0/0no passive-interface Serial1/0

10、no passive-interface Serial1/1network 2.0.0.0network 192.168.12.0network 192.168.23.0network 192.168.25.0no auto-summaryR3配置：router ospf 1/配置OSPFrouter-id 3.3.3.3redistribute rip metric 1000 metric-type 1 subnets tag 3 route-map 11/重发布配置ROUTE-MPA的RIP到OSPF中，并打上标记3passive-interface defaultno passive-i

11、nterface Serial1/1network 3.3.3.3 0.0.0.0 area 0network 192.168.34.0 0.0.0.255 area 0distance ospf external 170/配置OSPF外部区域的管理距离为170router rip/配置RIPversion 2redistribute ospf 1 metric 5/重发布OSPF到RIP中passive-interface defaultno passive-interface Serial1/0network 192.168.23.0no auto-summaryaccess-list 1

12、0 permit 11.11.11.11/定义感兴趣流route-map 11 permit 10/创建ROUTE-MAPmatch ip address 10/匹配流量set metric 500/设定开销为500route-map 3 deny 10/过滤匹配流量match tag 5/匹配打标记的流量route-map 3 permit 20/允许其它所有流量通过R4配置：router ospf 1/配置OSPFrouter-id 4.4.4.4passive-interface defaultno passive-interface Serial1/0no passive-interf

13、ace Serial1/1network 4.4.4.4 0.0.0.0 area 0network 192.168.34.0 0.0.0.255 area 0network 192.168.45.0 0.0.0.255 area 0R5配置：router ospf 1/配置OSPFrouter-id 5.5.5.5redistribute rip metric 1000 metric-type 1 subnets tag 5/重发布RIP到OSPF中，并打上标记3 passive-interface defaultno passive-interface Serial1/0network 5

14、.5.5.5 0.0.0.0 area 0network 192.168.45.0 0.0.0.255 area 0distance ospf external 170/配置OSPF外部区域的管理距离为170router rip/配置RIPversion 2redistribute ospf 1 metric 5/重分布OSPF到RIPpassive-interface defaultno passive-interface Serial1/1network 192.168.25.0no auto-summaryroute-map 5 deny 10/过滤匹配流量match tag 3/匹配打

15、标记的流量route-map 5 permit 20/允许其它所有流量通过实验结果分析：R5的路由表：R 192.168.12.0/24 120/1 via 192.168.25.1, 00:00:12, Serial1/1 1.0.0.0/32 is subnetted, 1 subnetsR 1.1.1.1 120/2 via 192.168.25.1, 00:00:12, Serial1/1 3.0.0.0/32 is subnetted, 1 subnetsO 3.3.3.3 110/129 via 192.168.45.2, 00:00:28, Serial1/0C 192.168.

16、45.0/24 is directly connected, Serial1/0C 192.168.25.0/24 is directly connected, Serial1/1 4.0.0.0/32 is subnetted, 1 subnetsO 4.4.4.4 110/65 via 192.168.45.2, 00:00:28, Serial1/0 5.0.0.0/32 is subnetted, 1 subnetsC 5.5.5.5 is directly connected, Loopback0O E1 192.168.23.0/24 110/1128 via 192.168.45

17、.2, 00:00:28, Serial1/0 11.0.0.0/32 is subnetted, 1 subnetsR 11.11.11.11 120/2 via 192.168.25.1, 00:00:12, Serial1/1O 192.168.34.0/24 110/128 via 192.168.45.2, 00:00:29, Serial1/0R3的路由表：O E1 192.168.12.0/24 110/1128 via 192.168.34.2, 00:01:53, Serial1/1 1.0.0.0/32 is subnetted, 1 subnetsO E1 1.1.1.1

18、 110/1128 via 192.168.34.2, 00:01:53, Serial1/1 3.0.0.0/32 is subnetted, 1 subnetsC 3.3.3.3 is directly connected, Loopback0O 192.168.45.0/24 110/128 via 192.168.34.2, 00:01:53, Serial1/1O E1 192.168.25.0/24 110/1128 via 192.168.34.2, 00:01:53, Serial1/1 4.0.0.0/32 is subnetted, 1 subnetsO 4.4.4.4 1

19、10/65 via 192.168.34.2, 00:01:53, Serial1/1 5.0.0.0/32 is subnetted, 1 subnetsO 5.5.5.5 110/129 via 192.168.34.2, 00:01:53, Serial1/1C 192.168.23.0/24 is directly connected, Serial1/0 11.0.0.0/32 is subnetted, 1 subnetsO E1 11.11.11.11 110/1128 via 192.168.34.2, 00:01:53, Serial1/1C 192.168.34.0/24

20、is directly connected, Serial1/1在上面的路由表中，R5、R3的部分路由出现了次佳路由，R3去往外部的非直连路由都将下一跳交给了R,显然不是最佳路由，为什么会出现次佳路由及解决方法，我们一起来分析一下：路由表中出现的O E1路由显然是通过OSPF学习到的，我们查看一下OSPFLSDB Type-5 AS External Link StatesLink ID ADV Router Age Seq# Checksum Tag1.1.1.1 5.5.5.5 499 0x80000001 0x000B26 011.11.11.11 5.5.5.5 499 0x80000

21、001 0x003DCB 0192.168.12.0 5.5.5.5 499 0x80000003 0x00FEBE 0192.168.23.0 3.3.3.3 484 0x80000001 0x00C5F6 0192.168.25.0 5.5.5.5 499 0x80000003 0x006F41 0显然都是R5通告过来的路由我们看一下R4的路由表和LSDB：O E1 192.168.12.0/24 110/1064 via 192.168.45.1, 00:10:11, Serial1/1 1.0.0.0/32 is subnetted, 1 subnetsO E1 1.1.1.1 110

22、/1064 via 192.168.45.1, 00:10:11, Serial1/1 3.0.0.0/32 is subnetted, 1 subnetsO 3.3.3.3 110/65 via 192.168.34.1, 00:10:11, Serial1/0O E1 192.168.25.0/24 110/1064 via 192.168.45.1, 00:10:11, Serial1/1 5.0.0.0/32 is subnetted, 1 subnetsO 5.5.5.5 110/65 via 192.168.45.1, 00:10:11, Serial1/1O E1 192.168

23、.23.0/24 110/1064 via 192.168.34.1, 00:10:11, Serial1/0 11.0.0.0/32 is subnetted, 1 subnetsO E1 11.11.11.11 110/1064 via 192.168.45.1, 00:10:11, Serial1/1 Type-5 AS External Link StatesLink ID ADV Router Age Seq# Checksum Tag1.1.1.1 5.5.5.5 711 0x80000001 0x000B26 011.11.11.11 5.5.5.5 711 0x80000001

24、 0x003DCB 0192.168.12.0 5.5.5.5 711 0x80000003 0x00FEBE 0192.168.23.0 3.3.3.3 698 0x80000001 0x00C5F6 0192.168.25.0 5.5.5.5 711 0x80000003 0x006F41 0从路由表和LSDB中我们可以看出，R4学习到外部路由除（R3直连外）都是R5通告的，为什么没有收到R3的通告呢？显然是R3没有通告其它5类LSA。从R3上的路由表没有RIP路由我们可以得知，由于OSPF的管理距离为110而RIP的为120,所以OSPF的路由优于RIP，所以全局路由表中只有OSPF的5

25、类路由，形成了次佳路由，由于全局路由表中没有RIP路由，所以它不能发出那些外部路由的5类LSA，所以在R4也不能形成负载均衡。至于只有R产生次佳路由，原因是R5先重发布而发出5类LSA，被R3学习到导致R3的RIP不能进全局路由表，也就不会有那些路由的5类LSA通告（只有直连外部路由通告），所以生成R3、R5上的部分次佳路由。解决方法：1.在RT3和RT5上过滤掉外部路由2.修改OSPF外部路由的管理距离，使之低于RIP思考哪个方法更优？方法1：R5：redistribute rip metric 1000 metric-type 1 subnets tag 5/在R5上重分布进来的RIP路由

26、打一标记5 Type-5 AS External Link StatesLink ID ADV Router Age Seq# Checksum Tag1.1.1.1 5.5.5.5 97 0x80000003 0x0061C8 511.11.11.11 5.5.5.5 97 0x80000003 0x00936E 5192.168.12.0 5.5.5.5 97 0x80000005 0x005561 5192.168.23.0 3.3.3.3 314 0x80000002 0x00C3F7 0192.168.25.0 5.5.5.5 97 0x80000005 0x00C5E3 5R3收到

27、Tag标记的5类LSAR3：route-map 5 deny 10/建立router-map 5过滤匹配的路由match tag 5/匹配带5标记的路由route-map 5 permit 20/允许其它的路由通过router ospf 1distribute-list route-map 5 in /在OSPF进程中过滤带标记的路由安装到全局路由表现在R3的路由表中没有次佳路由了R 192.168.12.0/24 120/1 via 192.168.23.1, 00:00:00, Serial1/0 1.0.0.0/32 is subnetted, 1 subnetsR 1.1.1.1 12

28、0/2 via 192.168.23.1, 00:00:00, Serial1/0 3.0.0.0/32 is subnetted, 1 subnetsC 3.3.3.3 is directly connected, Loopback0O 192.168.45.0/24 110/128 via 192.168.34.2, 00:00:08, Serial1/1R 192.168.25.0/24 120/1 via 192.168.23.1, 00:00:00, Serial1/0 4.0.0.0/32 is subnetted, 1 subnetsO 4.4.4.4 110/65 via 192.168.34.2, 00:00: