Internal Ethernet interface configuration

 interface FastEthernet 0/1

  description internal interface

 ip address

  ip nat inside

 no shut


We have configure an IP address on the internal interface and specified it as the Inside NAT interface

 External Ethernet interface configuration

Interface FastEthernet 0/0

 Description DSL interface

 no ip address

 pppoe enable

 pppoe-client dial-pool-number 1

 no shut


We have enabled PPPoE on the interface connected to the ISP and associated a dialer interface with it.

 Dialer interface configuration

interface Dialer1

 ip address negotiated

 ip mtu 1492

 ip nat outside

 encapsulation ppp

 dialer pool 1

 ppp authentication chap pap callin

 ppp pap sent-username USERNAME password P@ssw0rd

 ppp chap hostname HOSTNAME

 ppp chap password P@ssw0rd

 no shut


Dialer Interface configuration includes PPP negotiation and authentication information.

 Configuring Access List

ip access-list extended NAT_ACL 100 permit ip any


This access-list matches traffic that should be translated to the Dialer Interface IP address for Internet access


NAT/PAT configuration

ip nat inside source list NAT_ACL interface dialer 1 overload


NAT configuration for translating traffic matched in the above ACL to Dialer Interface IP address


DHCP server services configuration

ip dhcp pool LAN_DHCP

network /24




DHCP Server Configuration for assigning the IP address and other parameters to LAN users


Static default route configuration

ip route dialer 1

Finally a static default route is added that points towards the Dialer Interface.