1. 配置接口IP地址
[AR1-GigabitEthernet0/0/0]ip add 20.1.1.1 24
[AR2-GigabitEthernet0/0/0]ip add 20.1.1.2 24
[AR2-GigabitEthernet0/0/1]ip add 30.1.1.2 24
[AR3-GigabitEthernet0/0/0]ip add 30.1.1.3 24
[AR3-GigabitEthernet0/0/1]ip add 40.1.1.3 24
[AR4-GigabitEthernet0/0/0]ip add 40.1.1.4 24
2. 配置设备间使用RIP路由，进程为1
[AR1]rip 1
[AR1-rip-1]version 2
[AR1-rip-1]network 20.0.0.0
[AR2]rip 1
[AR2-rip-1]version 2
[AR2-rip-1]network 20.0.0.0
[AR2-rip-1]network 30.0.0.0
[AR3]rip 1
[AR3-rip-1]version 2
[AR3-rip-1]network 30.0.0.0
[AR3-rip-1]network 40.0.0.0
[AR4]rip 1
[AR4-rip-1]version 2
[AR4-rip-1]network 40.0.0.0
3. 配置Tunnel接口
[AR1]int Tunnel 0/0/1
[AR1-Tunnel0/0/1]tunnel-protocol gre
[AR1-Tunnel0/0/1]ip add 50.1.1.1 24
[AR1-Tunnel0/0/1]source 20.1.1.1
[AR1-Tunnel0/0/1]destination 30.1.1.3
[AR3]interface Tunnel 0/0/1
[AR3-Tunnel0/0/1]tunnel-protocol gre
[AR3-Tunnel0/0/1]ip add 50.1.1.3 24
[AR3-Tunnel0/0/1]source 30.1.1.3
[AR3-Tunnel0/0/1]destination 20.1.1.1
4. 配置Tunnel接口使用RIP路由，进程为2
[AR1]rip 2
[AR1-rip-2]version 2
[AR1-rip-2]network 50.0.0.0
[AR3]rip 2
[AR3-rip-2]version 2
[AR3-rip-2]network 50.0.0.0
5. 检查配置: 看到目的地址为对端设备的路由，其Cost值为1
