我们先做如下配置看看是什么结果：
R1：
R1(config)#int f0/0  
R1(config-if)#ip address 172.16.1.254 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#int s1/0
R1(config-if)#ip address 192.1.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#network 172.16.1.0
R1(config-router)#network 192.1.1.0
R2：
R2(config)#int s1/0
R2(config-if)#ip address 192.1.1.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#clock rate 64000
R2(config-if)#int s1/1
R2(config-if)#ip address 193.1.1.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#clock rate 64000
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#network 192.1.1.0
R2(config-router)#network 193.1.1.0
R3：
R3(config)#int s1/1
R3(config-if)#ip address 193.1.1.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#int f0/0
R3(config-if)#ip address 172.16.2.254 255.255.255.0
R3(config-if)#no shutdown
R3(config)#router rip
R3(config-router)#version 2
R3(config-router)#network 193.1.1.0
R3(config-router)#network 172.1.2.0
我们查看一下各个路由器的路由表：
R1：
R1#show ip route
Codes: C – connected, S – static, 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
       i – IS-IS, su – IS-IS summary, 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
     172.16.0.0/24 is subnetted, 1 subnets
C       172.16.1.0 is directly connected, FastEthernet0/0
R    193.1.1.0/24 [120/1] via 192.1.1.2, 00:00:01, Serial1/0
C    192.1.1.0/24 is directly connected, Serial1/0
R2：
R2#show ip route
Codes: C – connected, S – static, 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
       i – IS-IS, su – IS-IS summary, 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    172.16.0.0/16 [120/1] via 192.1.1.1, 00:00:07, Serial1/0
C    193.1.1.0/24 is directly connected, Serial1/1
C    192.1.1.0/24 is directly connected, Serial1/0
R3#show ip route
Codes: C – connected, S – static, 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
       i – IS-IS, su – IS-IS summary, 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
     172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
R       172.16.0.0/16 [120/2] via 193.1.1.1, 00:00:29, Serial1/1
C       172.16.2.0/24 is directly connected, FastEthernet0/0
C    193.1.1.0/24 is directly connected, Serial1/1
R    192.1.1.0/24 [120/1] via 193.1.1.1, 00:00:29, Serial1/1
在R1和R2的路由表中没有R3路由器F0/0口直连的网段信息
我们在R2中用调试工具查看一下：
R2：
R2#debug ip rip
RIP protocol debugging is on
R2#
*Mar  1 00:19:21.079: RIP: sending v2 update to 224.0.0.9 via Serial1/1 (193.1.1.1)
*Mar  1 00:19:21.083: RIP: build update entries
*Mar  1 00:19:21.083:   172.16.0.0/16 via 0.0.0.0, metric 2, tag 0
*Mar  1 00:19:21.087:   192.1.1.0/24 via 0.0.0.0, metric 1, tag 0
R2#
*Mar  1 00:19:22.683: RIP: received v2 update from 192.1.1.1 on Serial1/0
*Mar  1 00:19:22.687:      172.16.0.0/16 via 0.0.0.0 in 1 hops
R2#
*Mar  1 00:19:25.635: RIP: sending v2 update to 224.0.0.9 via Serial1/0 (192.1.1.2)
*Mar  1 00:19:25.639: RIP: build update entries
*Mar  1 00:19:25.639:   193.1.1.0/24 via 0.0.0.0, metric 1, tag 0
R2#
*Mar  1 00:19:48.395: RIP: received v2 update from 192.1.1.1 on Serial1/0
*Mar  1 00:19:48.399:      172.16.0.0/16 via 0.0.0.0 in 1 hops
可以看到R2只从S1/0口收到了R1的更新，S1/1口的更新没有收到,这是因为我们没有关闭路由器的自动汇总，所以完整的操作是下面这样：
R1：
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#network 172.16.1.254
R1(config-router)#network 172.16.1.0
R1(config-router)#network 192.1.1.0
R1(config-router)#no auto-summary
R2：
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#network 192.1.1.0
R2(config-router)#network 193.1.1.0
R2(config-router)#no auto-sum
R2(config-router)#no auto-summary
R3：
R3(config)#router rip
R3(config-router)#version 2
R3(config-router)#network 193.1.1.0
R3(config-router)#network 172.16.2.0
R3(config-router)#no auto-summary
我们再查看一下R2的路由表：
R2：
R2#show ip route
Codes: C – connected, S – static, 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
       i – IS-IS, su – IS-IS summary, 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
     172.16.0.0/24 is subnetted, 2 subnets
R       172.16.1.0 [120/1] via 192.1.1.1, 00:00:23, Serial1/0
R       172.16.2.0 [120/1] via 193.1.1.2, 00:00:16, Serial1/1
C    193.1.1.0/24 is directly connected, Serial1/1
C    192.1.1.0/24 is directly connected, Serial1/0
可以看到到达172.16.1.0和172.16.2.0网段有各自的路径拉
在R2路由器上用调试命令再来查看一下：
R2：
R2#debug ip rip
RIP protocol debugging is on
R2#
*Mar  1 00:40:34.927: RIP: sending v2 update to 224.0.0.9 via Serial1/1 (193.1.1.1)
*Mar  1 00:40:34.931: RIP: build update entries
*Mar  1 00:40:34.931:   172.16.1.0/24 via 0.0.0.0, metric 2, tag 0
*Mar  1 00:40:34.931:   192.1.1.0/24 via 0.0.0.0, metric 1, tag 0
*Mar  1 00:40:35.499: RIP: sending v2 update to 224.0.0.9 via Serial1/0 (192.1.1.2)
*Mar  1 00:40:35.503: RIP: build update entries
*Mar  1 00:40:35.503:   172.16.2.0/24 via 0.0.0.0, metric 2, tag 0
*Mar  1 00:40:35.507:   193.1.1.0/24 via 0.0.0.0, metric 1, tag 0
R2#
*Mar  1 00:40:38.175: RIP: received v2 update from 193.1.1.2 on Serial1/1
*Mar  1 00:40:38.179:      172.16.2.0/24 via 0.0.0.0 in 1 hops
R2#
*Mar  1 00:40:52.043: RIP: received v2 update from 192.1.1.1 on Serial1/0
*Mar  1 00:40:52.047:      172.16.1.0/24 via 0.0.0.0 in 1 hops
可以看到现在已经一切正常了
我们再用2台客户机测试一下连通性：
PC1#ping 172.16.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 260/288/340 ms