[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]ip add 192.168.1.1 24
[r1]int s4/0/0
[r1-Serial4/0/0]ip add 14.1.1.1 24
[r4]int l0
[r4-LoopBack0]ip add 4.4.4.4 24
[r4]int s3/0/0
[r4-Serial3/0/0]ip add 14.1.1.2 24
[r4-Serial3/0/0]link-protocol hdlc
Warning: The encapsulation protocol of the link will be changed. Continue? [Y/N]
:y
[r4]int s3/0/1
[r4-Serial3/0/1]ip add 24.1.1.2 24
[r4-Serial3/0/1]ppp authentication-mode pap
[r4]aaa
[r4-aaa]local-user a password cipher 123456
[r4-aaa]local-user a service-type ppp
[r4-aaa]local-user b password cipher 654321
[r4-aaa]local-user b service-type ppp
[r4]int s3/0/0
[r4-Serial3/0/0]shutdown
[r4-Serial3/0/0]undo shutdown
[r4]int s4/0/0
[r4-Serial4/0/0]ip add 34.1.1.2 24
[r4-Serial4/0/0]ppp
[r4-Serial4/0/0]ppp authentication-mode chap
[r4-Serial4/0/0]shutdown
[r4-Serial4/0/0]undo shutdown
[r1]int s4/0/0
[r1-Serial4/0/0]link-protocol hdlc
Warning: The encapsulation protocol of the link will be changed. Continue? [Y/N]
:y
[r2]int g0/0/1
[r2-GigabitEthernet0/0/1]ip add 192.168.2.1 24
[r2]int s4/0/0
[r2-Serial4/0/0]ip add 24.1.1.1 24
[r2-Serial4/0/0]ppp pap local-user a password cipher 123456
[r3]int g0/0/1
[r3-GigabitEthernet0/0/1]ip add 192.168.3.1 24
[r3]int s4/0/0
[r3-Serial4/0/0]ip add 34.1.1.1 24
[r3-Serial4/0/0]ppp chap user b
[r3-Serial4/0/0]ppp chap password cipher 654321
要求1-4搞定了
[r1]ip route-static 0.0.0.0 0 14.1.1.2
[r2]ip route-static 0.0.0.0 0 24.1.1.2
[r3]ip route-static 0.0.0.0 0 34.1.1.2
[r1]int Tunnel 0/0/0
[r1-Tunnel0/0/0]ip add 192.168.4.1 24
[r1-Tunnel0/0/0]tunnel-protocol gre p2mp
[r1-Tunnel0/0/0]source 14.1.1.1
[r1-Tunnel0/0/0]nhrp entry multicast dynamic
[r1-Tunnel0/0/0]nhrp network-id 100
[r2]int Tunnel 0/0/0
[r2-Tunnel0/0/0]ip add 192.168.4.2 24
[r2-Tunnel0/0/0]tunnel-protocol gre p2mp
[r2-Tunnel0/0/0]source Serial 4/0/0
[r2-Tunnel0/0/0]nhrp entry 192.168.4.1 14.1.1.1 register 
[r3]int Tunnel 0/0/0
[r3-Tunnel0/0/0]ip add 192.168.4.3 24
[r3-Tunnel0/0/0]tunnel-protocol gre p2mp
[r3-Tunnel0/0/0]source s4/0/0
[r3-Tunnel0/0/0]nhrp entry 192.168.4.1 14.1.1.1 register
[r1]rip 1
[r1-rip-1]ver 2
[r1-rip-1]network 192.168.1.0
[r1-rip-1]network 192.168.4.0
[r2]rip 1
[r2-rip-1]version 2
[r2-rip-1]network 192.168.4.0
[r2-rip-1]network 192.168.2.0
[r3]rip 1
[r3-rip-1]version 2
[r3-rip-1]network 192.168.4.0
[r3-rip-1]network 192.168.3.0
[r1]int Tunnel 0/0/0
[r1-Tunnel0/0/0]undo rip split-horizon （关闭这个口的水平分割）
[r1]acl 2000
[r1-acl-basic-2000]rule permit source 192.168.1.0 0.0.0.255
[r1]int s4/0/0
[r1-Serial4/0/0]nat outbound 2000