Configuring PPTP (VPDN) Server On A Cisco Router

1. Enable vpdn and define pptp parameters 
vpdn-group 1
! Default PPTP VPDN group
 accept-dialin
  protocol pptp
  virtual-template 1
!
2. setup the ip scheme for the dialin user
interface Virtual-Template1
 ip unnumbered Dot11Radio0.2
 peer default ip address pool PPTP-Pool
 no keepalive
 ip nat inside          <<<<<<<<<<<<<<<<<<<<add this is if you want dialin user use Internet
 ppp encrypt mppe 128
 ppp authentication ms-chap ms-chap-v2
!
3. specify the ip range
ip local pool PPTP-Pool 192.168.2.90 192.168.2.100

4. create username/password
username firewall password gfk$20!2


Ref:http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/329-cisco-router-pptp-server.html