The configurations of a DSL connection differ depending on the router type and the way that your provider implements the connection. For example, some providers use bridging rather than a dialer method. In the example we are using, our provider has given us a PVC of 1/100. For more information on what a PVC is, see the ATM section earlier in this chapter.
To configure the router, we enable Virtual Private Dialup Network (VPDN) and configure the virtual dialer interface, and the ATM interface itself. VPDN configures the router so that PPPoE requires "dial-in" in order to connect. Why is PPPoE configured as dial-in? Because it's the same PPP protocol that's used for authentication in dial-up connections, in this case running over Ethernet (which is the "oE" in PPPoE). The virtual dialer interface handles the IP address of the connection, the PPP authentication, and outside NAT information. Configuring the ATM interface simply entails applying the PVC value given to you by your ISP
!
hostname ournetworkrouter
!
! Enable VPDN
vpdn enable
no vpdn logging
!
! VPDN group pppoe requires "dialin". These commands configure
! a VPDN group called "pppoe" that is used to establish the PPPoE sesions
vpdn-group pppoe
! this command means that our router is the PPPoE client
! that is requesting to establish a PPPoE session
request-dialin
protocol pppoe
!
! Create a "virtual" interface that handles the "dialing" to the
! ISP's DSL line. This virtual interface is used on the ATM0 interface
interface Dialer1
ip address negotiated
! if you have a static IP address, replace the negoatiated line above
! with the provided IP address.
encapsulation ppp
! Adjust Mtu because 1492 + PPPoE headers = 1500
ip mtu 1492
ip nat outside
dialer pool 1
ppp authentication pap callin
! Our ISP gave us the username of bob1 and password of notsecure
ppp pap sent-username bob1 password notsecure
!
interface FastEthernet0
description Our local network interface
ip address 10.10.1.1 255.255.255.0
ip nat inside
!
! Our ISP gave us a PVC of 1/100. Depending on your ISP,
! you might get a different PVC
interface ATM0
description our DSL interface
no ip address
no atm ilmi-keepalive
dsl operating-mode auto
!
interface ATM0.1 point-to-point
pvc 1/100
protocol pppoe
! Tie this interface to the virtual Dialer Interface
pppoe-client dial-pool-number 1
!
! Configure NAT to use access-list 1 as the "source" traffic
! to perform NAT on
ip nat inside source list 1 interface Dialer1 overload
!
! Our default route is the virtual dialer interface
ip route 0.0.0.0 0.0.0.0 dialer1
!
! Used in the ip nat command
access-list 1 permit 10.10.1.0 0.0.0.255
If your ISP says to use CHAP for authentication, replace the PPP PAP commands with these:
ppp authentication chap callin
ppp chap hostname <username>
ppp chap password <password>