1，按照图示配置IP地址

r1：

r2：

r3：

2，在R1和R3配置默认路由使公网区域互通

[R1]ip route-static 0.0.0.0 0 100.1.1.2

R3]ip route-static 0.0.0.0 0 100.2.2.2

3，在R1和R3上配置GRE VPN，使两端私网能够互相访问，Tunnel口IP地址如图,隧道双up：

[R1-Tunnel0/0/0]tunnel-protocol gre	
[R1-Tunnel0/0/0]source 100.1.1.1
[R1-Tunnel0/0/0]destination 100.2.2.3

[R3-Tunnel0/0/0]tunnel-protocol gre 
[R3-Tunnel0/0/0]source 100.2.2.3
[R3-Tunnel0/0/0]destination 100.1.1.1

<R1>ping -a 192.168.3.1 192.168.3.3
  PING 192.168.3.3: 56  data bytes, press CTRL_C to break
    Request time out
    Reply from 192.168.3.3: bytes=56 Sequence=2 ttl=255 time=40 ms
    Reply from 192.168.3.3: bytes=56 Sequence=3 ttl=255 time=30 ms
    Reply from 192.168.3.3: bytes=56 Sequence=4 ttl=255 time=30 ms
    Reply from 192.168.3.3: bytes=56 Sequence=5 ttl=255 time=20 ms

  --- 192.168.3.3 ping statistics ---
    5 packet(s) transmitted
    4 packet(s) received
    20.00% packet loss
    round-trip min/avg/max = 20/30/40 ms

4，在R1和R3上配置RIPV2来传递两端私网路由

[R1]ip route-static 192.168.2.0 24 192.168.3.3

[R3]ip route-static 192.168.1.0 24 192.168.3.1

<R3>ping 192.168.1.1
  PING 192.168.1.1: 56  data bytes, press CTRL_C to break
    Request time out
    Reply from 192.168.1.1: bytes=56 Sequence=2 ttl=127 time=20 ms
    Reply from 192.168.1.1: bytes=56 Sequence=3 ttl=127 time=30 ms
    Reply from 192.168.1.1: bytes=56 Sequence=4 ttl=127 time=30 ms
    Reply from 192.168.1.1: bytes=56 Sequence=5 ttl=127 time=20 ms

  --- 192.168.1.1 ping statistics ---
    5 packet(s) transmitted
    4 packet(s) received
    20.00% packet loss
    round-trip min/avg/max = 20/25/30 ms