第一步

给PC1配置：

先给PC2配置：

第二部

给R1的接口配置ip

[R1]int g0/0/0
[R1-GigabitEthernet0/0/0]ip add 192.168.1.252 24

[R1-GigabitEthernet0/0/0]int g0/0/1
[R1-GigabitEthernet0/0/1]ip ad 100.1.1.1 24

给R2的接口配置IP

[R2]int g0/0/0
[R2-GigabitEthernet0/0/0]ip ad 100.1.1.2 24

[R2-GigabitEthernet0/0/0]int g0/0/1
[R2-GigabitEthernet0/0/1]ip ad 100.2.2.2 24

给R3的接口配置IP

[R3]int g0/0/0
[R3-GigabitEthernet0/0/0]ip ad 100.2.2.3 24

[R3-GigabitEthernet0/0/0]int g0/0/1
[R3-GigabitEthernet0/0/1]ip ad 192.168.2.252 24

弄公网通

给R1和R3配置静态路由

[R1]ip ro    
[R1]ip route-s    
[R1]ip route-static 0.0.0.0 0 100.1.1.2

[R3]ip rou    
[R3]ip route-s    
[R3]ip route-static 0.0.0.0 0 100.2.2.2

建立隧道口

[R1]int t    
[R1]int Tunnel 0/0/0
[R1-Tunnel0/0/0]ip ad 192.168.3.1 24

[R3]int t    
[R3]int Tunnel 0/0/0
[R3-Tunnel0/0/0]ip ad 192.168.3.3 24
[R3-Tunnel0/0/0]

配置隧道模式：

[R1-Tunnel0/0/0]tunnel-protocol gre

[R3-Tunnel0/0/0]tunnel-protocol gre

定义公网的源和目的IP地址

[R1-Tunnel0/0/0]source 100.1.1.1
[R1-Tunnel0/0/0]des    
[R1-Tunnel0/0/0]dest    
[R1-Tunnel0/0/0]destination  100.2.2.3

[R3-Tunnel0/0/0]sou    
[R3-Tunnel0/0/0]source 100.2.2.3
[R3-Tunnel0/0/0]dest    
[R3-Tunnel0/0/0]destination 100.1.1.1

配置静态路由协议：

[R1]ip rou    
[R1]ip route-s    
[R1]ip route-static 192.168.2.0 24 192.168.3.3

[R3]ip rou    
[R3]ip route-s    
[R3]ip route-static 192.168.1.0 24 192.168.3.1

随后在PC2上ping 192.168.1.1就可以通了