The link-protocol ppp command sets the link layer protocol encapsulated on an interface as PPP.
link-protocol ppp
None
Dialer interface view
2: Configuration level
# Set the link-layer protocol encapsulated on Dialer 0 as PPP.
<sysname> system-view [sysname] interface Dialer 0 [sysname-Dialer0] link-protocol ppp