R1的配置：
Router>en
Router#conf t
Router(config)#hostname R1
R1(config)#int f0/0
R1(config-if)#ip address 10.0.0.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#int s2/0
R1(config-if)#ip address 40.0.0.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#no auto-summary
R1(config-router)#network 10.0.0.0
R1(config-router)#network 40.0.0.0
R1(config-router)#exit
R1(config)#do wr
R2的配置：
Router>en
Router#conf t
Router(config)#hostname R2
R2(config)#int s2/0
R2(config-if)#ip address 40.0.0.2 255.255.255.0
R2(config-if)#clock rate 64000
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#int f0/0
R2(config-if)#ip address 20.0.0.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#int s3/0
R2(config-if)#ip address 50.0.0.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#no auto-summary
R2(config-router)#network 40.0.0.0
R2(config-router)#network 20.0.0.0
R2(config-router)#network 50.0.0.0
R2(config-router)#exit
R2(config)#do wr
R3的配置：
Router>en
Router#conf t
Router(config)#hostname R3
R3(config)#int s2/0
R3(config-if)#clock rate 64000
R3(config-if)#ip address 50.0.0.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#int f0/0
R3(config-if)#ip address 30.0.0.1 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#router rip
R3(config-router)#version 2
R3(config-router)#no auto-summary
R3(config-router)#network 50.0.0.0
R3(config-router)#network 30.0.0.0
R3(config-router)#exit
R3(config)#do wr