PPP over Ethernet 1

By certskills June 28, 2016 13:05

PPP over Ethernet (PPPoE) can be one of the more challenging configuration topics on the CCNA exam. Why? First, many network engineers ignore PPPoE as something that is configured only occasionally. Then, when faced with configuring it, you can follow a template that requires few unique parameters, and the choices of those parameters do not have an impact on the rest of the network. Plus there are several commands involved, commands seen only on the routers at the edge of the network. In short, it is easy to forget about PPPoE over time.

Today’s lab post hopes to help remedy that lack of PPPoE awareness at least in the context of CCNA exam prep. This lab gives you straightforward practice with a basic PPPoE configuration on the client side of the equation, with the ISP router already configured.


PPP over Ethernet (PPPoE) lets you create a PPP session over an Ethernet physical link. PPPoE can be particularly useful for Internet access links, because ISPs like some of the features of PPP (like CHAP authentication and PPP address assignment), but the physical link uses Ethernet rather than a serial link on the client side. For instance, a typical DSL connection from the home, with an external DSL modem, uses Ethernet from the router to the DSL modem: a classic case in which to use PPPoE.

This lab assumes that you might want to try this lab exercise on your own gear, VIRL, or on a simulator. To that end, the lab can use a crossover cable between the router acting as the PPPoE client router and the ISP router. These two routers would normally sit in different buildings, one owned by the customer and one owned by the ISP, with DSL or some other technology for an Internet access link between the routers. In a lab, to test the PPPoE configuration, the two routers just use an Ethernet link.

For this lab, build a client-side PPPoE configuration to match the following requirements. You do not need to worry about the ISP configuration at all, but it is listed in Example 1 for reference. The specific rules for this lab – all for the client router – are as follows:

  • Use the Dialer 10 interface
  • Use the Dialer Pool number 5
  • Configure the client to dynamically learn it’s IPv4 address on the PPPoE link using PPP protocols (it should learn if you try this in lab, per the ISP router’s initial configuration)
  • Configure the MTU to a value that considers the extra PPPoE headers
  • Use the ‘Wendell’ Authentication hostname and ‘Odom’ Authentication password. (The username/password combination is pre-configured; see Example 2 in this post.)
  • Configure a default route using the Dialer 10 interface as the outgoing interface
  • Assume all device interfaces shown in the lab are up, working and with correct IP addresses assigned (except for the Client interface connecting to the ISP).

Figure 1: Typical Lab Network for Testing PPPoE Configurations


Initial Configuration

Examples 1 and 2 show the beginning configuration state of ISP and Client devices.

Example 1: ISP Config


Example 2: Client Config


Answer on Paper, or Maybe Test in Lab

Next, write your answer on paper. Or if you have some real gear, or other tools, configure the lab with those tools.

To test your solution, if you happen to try it with CML/VIRL or real gear, you can verify the configuration and operation of the dialer interface by issuing the show interfaces dialer 10 command, you can verify the connectivity to the ISP by using the ping command. Also, on the client, try: show interfaces virtual-access 10, show interfaces virtual-access 10 configuration, and show pppoe session.


Do this Lab with Cisco’s CML (Formerly VIRL)

You can do these labs on paper and still get a lot out of the lab. As an extra help, we have added files for Cisco Modeling Lab – Personal (CML-P). CML-P replaces Cisco Virtual Internet Routing Lab (VIRL) software, in effect serving as VIRL Version 2.

Below, find two files: a file useful with CML-P and another useful with VIRL. (Note that the CML-P file has a .yaml filetype, while the older VIRL file has a VIRL filetype.) Once the file is loaded, CML-P or VIRL will create a lab topology similar to this lab’s topology, with the initial configuration shown in the lab as well.

This lab’s CML file!

This lab’s VIRL file!

The CML/VIRL topology matches this lab topology exactly.

Answers: Basic SNMP Config 1
Answers: PPP over Ethernet 1
By certskills June 28, 2016 13:05
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  1. Rick December 27, 19:31

    Great lab, did it on GNS3, Thanks for the practice

    Reply to this comment
  2. Efrain January 6, 23:37

    Gracias Wendell. Pude aclarar varias dudas con este laboratorio.

    ¡Dios te bendiga!


    Reply to this comment
  3. Marco January 2, 10:42

    GNS3 is not letting me input the ip dhcp negotiated command on the interface dialer 10, do you know why?

    Reply to this comment
    • certskills Author January 8, 10:05

      Hi Marco,
      I imagine you’ve already done so, but that’s really a question for GNS3 folks. I don’t have any input for you on GNS3, other than generic ideas. Generically, I’d say it’s an IOS version or feature set issue. That is, the code you’re running doesn’t support the command.

      Reply to this comment
  4. Alexander June 19, 19:32

    I’m trying to do the activity on Packet Tracer, but I’m no able to assign an IP address to the Virtual-Template interface. Is there a way around this?

    Reply to this comment
    • certskills Author June 19, 19:58

      I have a vague recollection (emphasis on vague) that PT doesn’t support it, and it sounds like that’s what you see. I personally don’t know a way around it; may just not be able to practice that feature with PT.

      Reply to this comment
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