Internal Ethernet interface configuration
interface FastEthernet 0/1
description internal interface
ip address 10.1.1.1 255.255.255.0
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 10.10.10.0 0.0.0.255 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 10.1.1.0 /24
dns-server 4.2.2.2
default-router 10.1.1.1
DHCP Server Configuration for assigning the IP address and other parameters to LAN users
Static default route configuration
ip route 0.0.0.0 0.0.0.0 dialer 1
Finally a static default route is added that points towards the Dialer Interface.