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 setup 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 if required, this is how to do it.

Now we will configure the ATM interface:

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Forum Replies

  1. Hi Rene,

    Thank you. I appreciate your very fast reply. I would appreciate if you could take a look to my explanation and tell if its ok and also answer some questions:

    ok so interface dialer is a type of logical interface / a some kind of entity where we store some settings / paramteres. under this logical interface we configure parameters like “encapsulation ppp” … “ppp chap password SECRET”. This entity is attached to a pool (dialer pool 1).

    interface dialer 1
    dialer pool 1

    In this pool we can include several physical interfaces as ATM :

    interface ATM 1/0

    ... Continue reading in our forum

  2. Hi Adrian,

    It sounds like you got it yes.

    The dialer interface is the logical interface where we configure all protocol stuff. Things like PPP, CHAP/PAP authentication, etc.

    A dialer interface can only belong to one dialer pool.

    In the dialer pool, we can have one or more physical interfaces…physical interfaces can belong to one or more dialer pools. That’s totally cool if you want to use it.

    When you use something like PPPoE, then it’s normally the CPE that “initiates” the connection. When the router has a packet with the dialer interface as the next hop, then

    ... Continue reading in our forum

  3. Hi Rene/Moderators,

    I am looking for a fuller understanding of the command “sh dsl interface atm 0”.
    Do you have a post for this?
    I searched dsl and arrived here…

  4. Hello Ian

    This command essentially displays information and statistics specific to the ADSL line.

    You can find more information about this at the following Cisco link.

    I hope this has been helpful!


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