Configuring Cisco Router with ADSL Modem (PPPoA / PPPoE) and NAT

This quick guide will show you how to configure a Cisco Router with external ADSL Modem using PPPoA or PPPoE.

Following is the sample configuration using Cisco 2900 with IOS image version 15.0(1r). Even though the example uses 2900 router, the configuration applies to 800, 1900, & 3900 Router.

Network Diagram

Configuration

LAN interface:

Configure your LAN interface with a static IP address.

int gi0/0
 description ADSL-LAN Interface
 ip address 172.16.0.1 255.255.0.0
 ip nat inside
 no shutdown

WAN interface:

Configure PPPoE client on your WAN Interface:

int gi0/1
 description ADSL-WAN Interface
 pppoe-client dial-pool-number 1
 no shutdown

Dialer interface:

Configure a dialer interface as follows:

int Dialer0
 encapsulation ppp
 dialer pool 1
 ip address negotiated
 ppp chap hostname YOUR_CHAP_LOGIN
 ppp chap password YOUR_CHAP_PASSWORD
 ip mtu 1492
 ip tcp adjust-mss 1452
 ip nat outside

NAT Configuration:

access-list 10 permit 172.16.0.0 0.0.255.255
ip nat inside source list 10 int dialer0 overload

Routing Configuration:

Put a static route for internet:

ip route 0.0.0.0 0.0.0.0 dialer0