#R1
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]un in en
Info: Information center is disabled.
[Huawei]sys R1
[R1]int Serial 4/0/0
[R1-Serial4/0/0]link-protocol PPP
[R1-Serial4/0/0]ip ad 12.1.1.1 24

#R2
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]un in en
Info: Information center is disabled.
[Huawei]sys R2
[R2]int se4/0/0
[R2-Serial4/0/0]li  
[R2-Serial4/0/0]link-protocol PPP
[R2-Serial4/0/0]ip add 12.1.1.2 24
#R1 ping R2抓包查看二层协议封装