conf t

vpdn group PPPoE request dialout pppoe
vpdn group PPPoE localname ISP.USERNAME
vpdn group PPPoE ppp authentication pap
vpdn username ISP.USERNAME password Password_of_ISP.USERNAME

int gi1/1nameif outside
security-level 0
pppoe client vpdn group PPPoE
ip address pppoe setroute
ipv6 nd suppress-ra
shut
no shut
exit