R1：
[R1]aaa
[R1-aaa]local-user huawei password cipher huawei123
[R1-aaa]local-user huawei service-type ppp
[R1-aaa]int s0/0/0
[R1-Serial0/0/0]link-protocol ppp
[R1-Serial0/0/0]ppp authentication-mode pap
[R1-Serial0/0/0]ip ad 10.1.1.1 30
R2：
[R2-Serial0/0/0]link-protocol ppp
[R2-Serial0/0/0]ppp pap local-user huawei password cipher huawei123
[R2-Serial0/0/0]ip ad 10.1.1.2 30
