PPPOA DSL on Cisco IOS Router

The configuration of DSL on a Cisco IOS router can be quite confusing for people who haven’t worked much with Cisco routers before or didn’t have to worry about DSL settings because the ISP provided the DSL modem. In this short lesson, I will explain the steps required to get a working DSL connection.

I will only focus on the configuration of DSL, we will not dive into other things like NAT/PAT or the configuration of DHCP.

To get a working DSL connection there are a number of things we have to deal with:

  • Configure a dialer interface.
  • Apply PPP configuration and layer 3 settings to the dialer interface.
  • Apply the ATM configuration to the ATM interface.
  • Link the ATM interface to the dialer interface.
  • Configure a default route to route traffic out of the dialer interface.

Let me walk you through the configuration:

First, we will configure a dialer interface that has all PPP settings:

Router(config)#interface dialer 1
Router(config-if)#encapsulation ppp
Router(config-if)#ip address negotiated
Router(config-if)#dialer pool 1

Router(config-if)#ppp authentication chap callin
Router(config-if)#ppp chap hostname MYUSERNAME
Router(config-if)#ppp chap password SECRET

First, we will tell the dialer interface to use PPP encapsulation and that we want to receive an IP address from the ISP through PPP. The dialer pool command tells the dialer interface that when it wants to set up a connection, it has to use a member interface of the “dialer pool”. We’ll configure the ATM interface as a member of this pool in a bit.

We also configured the dialer interface to use CHAP authentication with username ‘MYUSERNAME’ and  ‘MYSECRET’ as password. Not all ISPs will require authentication, but this is how to do it if required.

Now we will configure the ATM interface:

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Forum Replies

  1. Hi, René, first sorry for my broken English but I am a Spanish speaker, let me tell you that your explain are excellent about the dsl configuration, but I have a doubt I am trying to configure two router cisco 857 back to back another way to say that you know is stand alone, or it is necessary something clock signal from DSLAM to ADSL router, it is just an idea because here I have a case where two building have just two wire connection between them, what do you think is it possible or not, I was trying but it doesn´t work maybe you can help me .

    Thank you a

    ... Continue reading in our forum

  2. Hi Nelson,

    As far as I know it’s only possible to configure back-to-back DSL using G.SHDSL, you can’t do it with ADSL because it’s asymmetric. G.SHDSL is symmetric.

    If you have an ATM interface that supports G.SHDSL you can try this:

    interface ATM0/0
    dsl equipment-type ?

    If it supports this command, you should be able to run back-to-back.


  3. Hello Rene,

    could you please draw the dsl connection on while using modem and while using router ?

    how the network connection ?

  4. Hi Gaganpal,

    What do you mean exactly?


  5. Hi Rene,

    “we will configure a dialer interface that has all PPP settings”.
    OK we are configuring it but can you please explain WHAT IS a “dialer interface”? A logical interface that DIALS somewhere (where?) something (what?)?
    Or an interface in which someone dials into?
    Thank you!


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