RIP offset-list
RIP offset-list
RIP的offset-list实验拓扑图如下： 图1：offset-list实验拓扑图 首先,按照上图配置一下，把RIP配通。这里就不做详细的说明了。 配置offset-list： r1(config)#router rip r1(config-router)#offset-l 1 in 16 s1/0 r1(config-router)#end r1#sh ip ro Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/24 is subnetted, 1 subnets //所有的RIP的路由信息都没有了，因为已经把跳数改为16跳，即不可达。 C 1.1.1.0 is directly connected, Loopback0 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial1/0 r1#sh ru Building configuration... Current configuration : 614 bytes ! version 12.2 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname r1 ! ! clock timezone CST 8 ip subnet-zero no ip domain lookup ! ! ! ! interface Loopback0 ip address 1.1.1.1 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial1/0 ip address 12.1.1.1 255.255.255.0 ! interface Serial2/0 no ip address shutdown ! router rip offset-list 1 in 16 Serial1/0 network 1.0.0.0 network 12.0.0.0 ! ip classless no ip http server ! ! ! ! ! line con 0 exec-timeout 0 0 logging synchronous line aux 0 line vty 0 4 ! End Offset-list命令就是手工把协议的Matric值修改了。 通过这个实验得知，在正常没有人工配置任何破环机制的情况下，RIP知道一个接口或网断16跳，即不可达。它会立即删除路由表里的对应项，然后把这个信息转发给自己的下一跳路由器。 删除16跳修改取消后在改为8跳。 用offset-list 1 in 8 Serial1/0在原来的基础之上加8跳，而不是改为8跳。 r1#conf t Enter configuration commands, one per line. End with CNTL/Z. r1(config)#router rip r1(config-router)#offset-l 1 in 8 s1/0 r1(config-router)#end 更新前： r1#sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/24 is subnetted, 1 subnets C 1.1.1.0 is directly connected, Loopback0 R 2.0.0.0/8 [120/1] via 12.1.1.2, 00:00:27, Serial1/0 R 3.0.0.0/8 [120/2] via 12.1.1.2, 00:00:27, Serial1/0 R 5.0.0.0/8 [120/1] via 12.1.1.2, 00:00:27, Serial1/0 R 23.0.0.0/8 [120/1] via 12.1.1.2, 00:00:27, Serial1/0 R 8.0.0.0/8 [120/1] via 12.1.1.2, 00:00:27, Serial1/0 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial1/0 更新后： r1#sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/24 is subnetted, 1 subnets C 1.1.1.0 is directly connected, Loopback0 R 2.0.0.0/8 [120/9] via 12.1.1.2, 00:00:05, Serial1/0 R 3.0.0.0/8 [120/10] via 12.1.1.2, 00:00:05, Serial1/0 R 5.0.0.0/8 [120/9] via 12.1.1.2, 00:00:05, Serial1/0 R 23.0.0.0/8 [120/9] via 12.1.1.2, 00:00:05, Serial1/0 R 8.0.0.0/8 [120/9] via 12.1.1.2, 00:00:05, Serial1/0 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial1/0 把更新前和更新后的路由表对比一下便不难得出结论。他自己的路由表全加上了8跳。 R2的路由表信息 r2#sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 1.0.0.0/8 [120/1] via 12.1.1.1, 00:00:09, Serial2/0 2.0.0.0/24 is subnetted, 1 subnets C 2.2.2.0 is directly connected, Loopback0 R 3.0.0.0/8 [120/1] via 23.1.1.3, 00:00:24, Serial1/0 5.0.0.0/24 is subnetted, 1 subnets C 5.5.5.0 is directly connected, Loopback1 23.0.0.0/24 is subnetted, 1 subnets C 23.1.1.0 is directly connected, Serial1/0 8.0.0.0/24 is subnetted, 1 subnets C 8.8.8.0 is directly connected, Loopback2 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial2/0 R3的路由表信息 r3# sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 1.0.0.0/8 [120/2] via 23.1.1.2, 00:00:00, Serial2/0 R 2.0.0.0/8 [120/1] via 23.1.1.2, 00:00:00, Serial2/0 3.0.0.0/24 is subnetted, 1 subnets C 3.3.3.0 is directly connected, Loopback0 R 5.0.0.0/8 [120/1] via 23.1.1.2, 00:00:00, Serial2/0 23.0.0.0/24 is subnetted, 1 subnets C 23.1.1.0 is directly connected, Serial2/0 R 8.0.0.0/8 [120/1] via 23.1.1.2, 00:00:00, Serial2/0 R 12.0.0.0/8 [120/1] via 23.1.1.2, 00:00:00, Serial2/0 把R2和R3的路由表信息与R1的信息对比便知，如果命令里是in那么R2的R3的路由表里的跳数是不会变的。 要取消修改用r1(config-router)#no offset-l 1 in 8 s1/0 下面在看一下修改为out的情况 在R1上： r1(config)#router rip r1(config-router)#offset-l 1 out 8 s1/0 r1(config-router)#end R1的路由表信息 r1#sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/24 is subnetted, 1 subnets C 1.1.1.0 is directly connected, Loopback0 R 2.0.0.0/8 [120/1] via 12.1.1.2, 00:00:02, Serial1/0 R 3.0.0.0/8 [120/2] via 12.1.1.2, 00:00:02, Serial1/0 R 5.0.0.0/8 [120/1] via 12.1.1.2, 00:00:02, Serial1/0 R 23.0.0.0/8 [120/1] via 12.1.1.2, 00:00:02, Serial1/0 R 8.0.0.0/8 [120/1] via 12.1.1.2, 00:00:02, Serial1/0 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial1/0 R1自身路由表的信息没有变化。 R2的路由表信息 r2#sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 1.0.0.0/8 [120/9] via 12.1.1.1, 00:00:04, Serial2/0 2.0.0.0/24 is subnetted, 1 subnets C 2.2.2.0 is directly connected, Loopback0 R 3.0.0.0/8 [120/1] via 23.1.1.3, 00:00:23, Serial1/0 5.0.0.0/24 is subnetted, 1 subnets C 5.5.5.0 is directly connected, Loopback1 23.0.0.0/24 is subnetted, 1 subnets C 23.1.1.0 is directly connected, Serial1/0 8.0.0.0/24 is subnetted, 1 subnets C 8.8.8.0 is directly connected, Loopback2 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, Serial2/0 R3的路由表信息 r3# sh ip rou Codes: C - connected, S - static, I - IGRP, R - RIP, M - 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 1.0.0.0/8 [120/10] via 23.1.1.2, 00:00:18, Serial2/0 R 2.0.0.0/8 [120/1] via 23.1.1.2, 00:00:18, Serial2/0 3.0.0.0/24 is subnetted, 1 subnets C 3.3.3.0 is directly connected, Loopback0 R 5.0.0.0/8 [120/1] via 23.1.1.2, 00:00:18, Serial2/0 23.0.0.0/24 is subnetted, 1 subnets C 23.1.1.0 is directly connected, Serial2/0 R 8.0.0.0/8 [120/1] via 23.1.1.2, 00:00:18, Serial2/0 R 12.0.0.0/8 [120/1] via 23.1.1.2, 00:00:18, Serial2/0 而其他的路由器针对R1的条目信息发生了变化。 通过上边的两个尝试得知，命令中in和out的区别： 区别是in或out都是把定义自己是第8跳。所不同的是in是在路由表信息进来的时候那个接口改的，自然其它路由器就不改了，当自身路由器的路由更新发出去的时候再减回去；而out是把发给其他路由器的条目修改了，所以其他路由器的条目也就随之更新了，而自己却不做任何修改，其他路由器更新发回来时它再减回去。也可以理解为in是在接口告诉进来的更新自己是第8跳，出去时再告诉更新自己是第0跳；而out则相反只告诉出去的更新自己是第8跳，进来的更新会告诉它自己是第0跳。 所以就出现下列现象， In时R1认为，R2是9，R3是10；而R3认为R2是1，R1是2； Out时R1认为，R2是1，R3是2；而R3认为R2是9，R1是10 |