Answers: PPP over Ethernet 1

By Chris June 29, 2016 13:10

The new ICND2 book takes extra care to map out the configuration required for PPPoE, along with the somewhat complex verification and troubleshooting details as well. This lab is meant to be straightforward so that you get practice on getting the configuration correct. The lab also lists a copy of a figure from the book that details the main configuration steps. (Here’s the lab post link.)


Figure 1: Typical Lab Network for Testing PPPoE Configurations


Example 1: Client Config



The new ICND2 200-105 book’s Chapter 15 (published 2016) takes a close look at PPPoE configuration. Interestingly, the client side configuration can look scary, with several unfamiliar commands. However, for parameters, all you have to do is select two parameters that just need to be unique on the local router, and then configure those numbers in the correct places. The numbers are the dialer interface number and the dialer pool number.

This particular lab told you what values to use for each parameter, mainly to make it easier to list a single answer configuration here in the lab. Once armed with the dialer interface number of choice (10 in this case) and dialer pool number (5 in this case), you can just follow a template. You also need to know the same username/password combination that the ISP is expecting to hear from the client router as part of the PPP CHAP authentication exchange (Wendell/Odom in this case). Figure 2 shows the template:

Figure 2: Figure 15-28 from the ICND2 200-105 Cert Guide


If you use the template in the figure, and compare it to the answer in Example 1, you will find all the commands. Here are some important highlights:

  • The physical interface (G0/1 in this case) has no layer 3 parameters at all, and even shows the no ip address command to emphasize that IP is not enabled on the physical interface.
  • IPv4 is enabled on the dialer interface, but in a way to use PPP address assignment, not DHCP address assignment, by using the ip address negotiated
  • The CHAP user and password sit under the dialer interface, which actually has more to do with the one-way authentication configured here (the ISP authenticates the client, but not vice versa).
  • The numbers that must match here are the dialer pool numbers (5 in this case).

Note that no one dialer interface number or dialer pool number is better than another. (Note that often an engineer will use the same dialer pool and dialer interface number just to make operations a little simpler.)

Answers: Interface PAT 1
GRE Tunnel 2
By Chris June 29, 2016 13:10
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  1. Luis March 4, 06:24

    Hi Mr Odom, I’ve a question for you 😀 I’ve been doing my owns labs of pppoe and always I put the commands of MTU and authentication below the dialer pool ¿The location of the command have any affect? or ¿my labs have been working fine for a bug of the simulators? I’ll attentive for your comments!

    Best regards from Chile

    Reply to this comment
    • certskills March 9, 09:29

      A question to clarify: your lab works, with the commands in the dialer pool, but not on the dialer interface… on real gear? Or is all your testing on a simulator? If on a simulator, then I can’t answer – it’s just too much time to go chasing issues with simulators. If on real gear, I’d be interested in the show run output from the routers on both ends of the link. Thanks, Wendell

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  2. Chris September 8, 23:26

    Hi Mr. Odom, I cannot find a main contact page on this site, but do you have anything published for the 210-260 CCNA Security?

    Reply to this comment
    • certskills September 13, 09:48

      Hi Chris,
      Thanks for the note! Nope, there’s not a general contact email etc here, other than my Certskills Twitter and Facebook accounts that are linked in different places here (look for the icons). Anyway, short answer is no, I don’t have any products in the security space. Thanks for asking…

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