Cisco ASR 9000 Series Command Reference Manual page 742

ppp authentication
RP/0/RSP0/CPU0:router(config-if)# encapsulation ppp
RP/0/RSP0/CPU0:router(config-if)# ppp authentication chap MIS-access
Related Commands
Command
aaa authentication ppp
encapsulation
username
Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference,
Release 5.3.x
722
PPP Commands onthe Cisco ASR 9000 Series Router
Description
Specifies one or more AAA authentication methods
for use on serial interfaces running PPP.
Sets the encapsulation method used by the interface.
Configures a new user with a username, establishes
a password, and grants permissions for the user.