r1int g0/0/1
r1-GigabitEthernet0/0/1ip add 192.168.1.1 24
r1int s4/0/0
r1-Serial4/0/0ip add 14.1.1.1 24
r4int l0
r4-LoopBack0ip add 4.4.4.4 24
r4int s3/0/0
r4-Serial3/0/0ip add 14.1.1.2 24
r4-Serial3/0/0link-protocol hdlc
Warning: The encapsulation protocol of the link will be changed. Continue? Y/N
:y
r4int s3/0/1
r4-Serial3/0/1ip add 24.1.1.2 24
r4-Serial3/0/1ppp authentication-mode pap
r4aaa
r4-aaalocal-user a password cipher 123456
r4-aaalocal-user a service-type ppp
r4-aaalocal-user b password cipher 654321
r4-aaalocal-user b service-type ppp
r4int s3/0/0
r4-Serial3/0/0shutdown
r4-Serial3/0/0undo shutdown
r4int s4/0/0
r4-Serial4/0/0ip add 34.1.1.2 24
r4-Serial4/0/0ppp
r4-Serial4/0/0ppp authentication-mode chap
r4-Serial4/0/0shutdown
r4-Serial4/0/0undo shutdown
r1int s4/0/0
r1-Serial4/0/0link-protocol hdlc
Warning: The encapsulation protocol of the link will be changed. Continue? Y/N
:y
r2int g0/0/1
r2-GigabitEthernet0/0/1ip add 192.168.2.1 24
r2int s4/0/0
r2-Serial4/0/0ip add 24.1.1.1 24
r2-Serial4/0/0ppp pap local-user a password cipher 123456
r3int g0/0/1
r3-GigabitEthernet0/0/1ip add 192.168.3.1 24
r3int s4/0/0
r3-Serial4/0/0ip add 34.1.1.1 24
r3-Serial4/0/0ppp chap user b
r3-Serial4/0/0ppp chap password cipher 654321
要求1-4搞定了
r1ip route-static 0.0.0.0 0 14.1.1.2
r2ip route-static 0.0.0.0 0 24.1.1.2
r3ip route-static 0.0.0.0 0 34.1.1.2
r1int Tunnel 0/0/0
r1-Tunnel0/0/0ip add 192.168.4.1 24
r1-Tunnel0/0/0tunnel-protocol gre p2mp
r1-Tunnel0/0/0source 14.1.1.1
r1-Tunnel0/0/0nhrp entry multicast dynamic
r1-Tunnel0/0/0nhrp network-id 100
r2int Tunnel 0/0/0
r2-Tunnel0/0/0ip add 192.168.4.2 24
r2-Tunnel0/0/0tunnel-protocol gre p2mp
r2-Tunnel0/0/0source Serial 4/0/0
r2-Tunnel0/0/0nhrp entry 192.168.4.1 14.1.1.1 register 
r3int Tunnel 0/0/0
r3-Tunnel0/0/0ip add 192.168.4.3 24
r3-Tunnel0/0/0tunnel-protocol gre p2mp
r3-Tunnel0/0/0source s4/0/0
r3-Tunnel0/0/0nhrp entry 192.168.4.1 14.1.1.1 register
r1rip 1
r1-rip-1ver 2
r1-rip-1network 192.168.1.0
r1-rip-1network 192.168.4.0
r2rip 1
r2-rip-1version 2
r2-rip-1network 192.168.4.0
r2-rip-1network 192.168.2.0
r3rip 1
r3-rip-1version 2
r3-rip-1network 192.168.4.0
r3-rip-1network 192.168.3.0
r1int Tunnel 0/0/0
r1-Tunnel0/0/0undo rip split-horizon （关闭这个口的水平分割）
r1acl 2000
r1-acl-basic-2000rule permit source 192.168.1.0 0.0.0.255
r1int s4/0/0
r1-Serial4/0/0nat outbound 2000