Cisco ADSL PPPoA Sample Configuration

!--- Comments contain explanations and additional information.

service timestamps debug datetime msec
service timestamps log datetime msec
ip subnet-zero
!
!--- For DHCP:
ip dhcp excluded-address ip dhcp pool network default-router dns-server
!
interface ethernet0
no shut
ip address
!--- For NAT:
ip nat inside
no ip directed-broadcast
!
interface atm0
no shut
no ip address
no ip directed-broadcast
no ip mroute-cache
pvc
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
!--- Common PVC values supported by ISPs are 0/35 or 8/35. !--- Confirm your PVC values with your ISP.
!
interface dialer1
ip address subnet mask           use  ip address negotiated, if dynamic address)
no ip directed-broadcast
!--- For NAT:
ip nat outside
encapsulation ppp
dialer pool 1
ppp chap hostname
ppp chap password
ppp pap sent-username password
!
!--- For NAT:
ip nat inside source list 1 interface dialer1 overload
!--- If you have a pool (a range) of public IP addresses provided !--- by your ISP, you can use a NAT Pool. Replace !--- ip nat inside source list 1 interface dialer1 overload

!--- with these two configuration statements: !--- ip nat inside source list 1 pool overload !--- ip nat pool !--- netmask

!--- If Internet users require access to an internal server, you can !--- add this static NAT configuration statement: !--- ip nat inside source static tcp {80 or 25} !--- {80 or 25} extendable !--- Note: TCP port 80 (HTTP/web) and TCP port 25 (SMTP/mail) are used !--- for this example. You can open other TCP or UDP ports, if needed.
!
ip classless
ip route 0.0.0.0 0.0.0.0 dialer1
!--- For NAT:
access-list 1 permit
!--- In this configuration, access-list 1 defines a standard access list !--- that permits the addresses that NAT translates. For example, if !--- your private IP network is 10.10.10.0, configure !--- access-list 1 permit 10.10.10.0 0.0.0.255 in order to allow NAT to translate !--- packets with source addresses between 10.10.10.0 and 10.10.10.255.
!
end


Source : Cisco.com