The document provides detailed instructions for configuring a Cisco router as a PPPoE client for DSL connectivity, covering both Ethernet and ATM interfaces. It outlines configuration steps, including setting up internal and external interfaces, dialing, NAT/PAT, and DHCP services. Additionally, it notes the importance of IP domain lookup and proper interface states for successful DSL connections.

1. Configuring a Cisco Router as a PPPoE Client for DSL connectivity
PPPoE: Point-to-Point Protocol over Ethernet. The PPP over Ethernet Client feature
provides PPP over Ethernet (PPPoE) Client support on routers on customer premises.
Configuring a Cisco routers as a PPPoE client for DSL connectivity, there are two cases,
one for the Ethernet interfaces, and another for the ATM interfaces
A. PPPoE on Ethernet interfaces—PPPoE functionality is configured on a CPE
router with two Ethernet interfaces. One Ethernet interface is subscriber-facing,
the other provider facing.
B. PPPoE on ATM interfaces—PPPoE functionality is configured on a CPE router
with one Ethernet interface and one ATM interface. The Ethernet interface is
subscriber-facing whereas the ATM interface is provider-facing.
Note: I noticed that on some books no one mentioned the configuration of IP domain
lookup command and ISP DNS options in DHCP server configuration. Without these
DSL connection will not work. Also pay attention if DSL connection did not work, to check
the state of all interfaces by using show ip interface brief and make sure to issue no
shutdown command on all of them.
A. PPPoE on Ethernet interfaces
DSL configuration brief steps:
1. Internal Ethernet interface configuration
2. External Ethernet interface configuration
3. Dialer interface configuration
4. Configuring Access List
5. NAT/PAT configuration
6. Configuring IP domain Lookup
7. DHCP server services configuration
8. Static default route configuration
DSL configuration detailed steps:
1. Internal Ethernet interface configuration
interface FastEthernet 0/1
description internal interface
ip address 172.16.1.1 255.255.255.0
1

2. ip nat inside
no shut
OR (incase you are using Cisco 877 router)
interface Vlan1
description internal interface
ip address 172.16.1.1 255.255.255.0
ip nat inside
no shut
2. External Ethernet interface configuration
Interface FastEthernet 0/0
Description DSL interface
no ip address
pppoe enable
pppoe-client dial-pool-number 1
no shut
3. 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 (this is the password that
ISP gave it to you
ppp chap hostname HOSTNAME (This is the username that ISP gave it to you)
ppp chap password P@ssw0rd
no shut
4. Configuring Access List
ip access-list extended DSL_ACCESSLIST
100 permit ip 10.10.10.0 0.0.0.255 any
5. Configuring NAT/PAT
ip nat inside source list DSL_ACCESSLIST interface dialer 1 overload
2

3. 6. Configuring IP domain Lookup
ip domain lookup
ip name-server Primary DNS IP address (obtained from your ISP)
ip name-server Secondary DNS IP address (obtained from your ISP)
7. DHCP server services configuration
ip dhcp pool DSL_DHCP
network 10.10.10.0 /29
dns-server Primary DNS IP address Secondary DNS IP address (obtained from your
ISP)
default-router 10.10.10.1 (internal VLAN or Ethernet interface Ip address)
import all
8. Static default route configuration
Finally, configure a static default route. It should point to the dialer interface rather
than an IP address as in the below example.
ip route 0.0.0.0 0.0.0.0 dialer 1
B. PPPoE on ATM interfaces
DSL configuration brief steps:
1. Internal Ethernet interface configuration
2. External ATM interface configuration (in case you are using Cisco 877 Router)
3. Dialer interface configuration
4. Configuring Access List
5. NAT/PAT configuration
6. Configuring IP domain Lookup
7. DHCP server services configuration
8. Static default route configuration
DSL configuration detailed steps:
1. Internal VLAN interface configuration (using Cisco 877 Router)
interface Vlan1
description internal interface
3

4. ip address 172.16.1.1 255.255.255.0
ip nat inside
no shut
OR (if you are using configurable internal Ethernet interface)
interface FastEthernet 0/1
description internal interface
ip address 172.16.1.1 255.255.255.0
ip nat inside
no shut
2. External ATM interface configuration
interface ATM 0
description DSL interface
ip directed-broadcast
ip mask-reply
ip route-cache flow
no ip address
dsl operating-mode auto
pvc 8/35
no shutdown
pppoe-client dial-pool-number 1
3. 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 (this is the password that
ISP gave it to you
ppp chap hostname HOSTNAME (This is the username that ISP gave it to you)
ppp chap password P@ssw0rd
no shut
4. Configuring Access List
ip access-list extended DSL_ACCESSLIST
4

5. 100 permit ip 10.10.10.0 0.0.0.255 any
5. Configuring NAT/PAT
ip nat inside source list DSL_ACCESSLIST interface dialer 1 overload
6. Configuring IP domain Lookup
ip domain lookup
ip name-server Primary DNS IP address (obtained from your ISP)
ip name-server Secondary DNS IP address (obtained from your ISP)
7. DHCP server services configuration
ip dhcp pool DSL_DHCP
network 10.10.10.0 /29
dns-server Primary DNS IP address Secondary DNS IP address (obtained from your
ISP)
default-router 10.10.10.1 (internal VLAN or Ethernet interface Ip address)
import all
8. Static default route configuration
Finally, configure a static default route. It should point to the dialer interface rather
than an IP address as in the below example.
ip route 0.0.0.0 0.0.0.0 dialer 1
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7. routers, Cisco firewalls, Cisco wireless products, Cisco modules and interface cards
products at competitive price and ship to worldwide.
Our website: http://www.3anetwork.com
Telephone: +852-3069-7733
Email: info@3Anetwork.com
Address: 23/F Lucky Plaza, 315-321 Lockhart Road, Wanchai, Hongkong
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