Multilink PPP 1

By Chris September 13, 2016 09:05

Multilink PPP (MLPPP) makes multiple parallel links act like one link from a layer 3 perspective. Then, when a router’s layer 3 routing decides to forward a layer 3 packet out the layer 3 MLPPP multilink interface, the router has to choose which of the several MLPPP-controlled links to use. To do that, the router’s MLPPP layer 2 logic takes over to load balance the message over the multiple links. This next lab gives you a chance to practice MLPPP configuration, starting from scratch, by configuring two serial links to be in one multilink PPP group. No muss, no fuss, just practice making MLPPP work on a pair of serial links.


Configure MLPPP on both router R1 and R2 in the figure, so that the routers have a single subnet ( used between the two routers. You should think of this lab as a complete configuration for MLPPP, but also think about any changes needed based on the initial configuration to this lab. Follow these requirements:

  • Configure the two serial links to use MLPPP:
    • Use MLPPP interface 1
    • Use subnet
    • Give R1 an IPv4 address that ends with .1, and R2 an address that ends with .2
    • Do not use any PPP authentication
  • As for the transition from the existing configuration, examine the initial configurations shown in this lab exercise, and decide whether or not any existing configuration needs to be updated as a result:
    • Check the OSPF configuration, and make changes as needed, so that both routers still become OSPF neighbors and still exchange routes for their LAN subnets
    • Check the IP addressing configuration to remove any IP address overlaps or remove any unnecessary IP addresses.
  • As for the topology:
    • Assume all interfaces shown in the figure are up and working


Figure 1: MLPPP Topology


Initial Configuration

Examples 1 and 2 show the initial configurations on routers R1 and R2, respectively.


Example 1: Router R1 Initial Configuration


Example 2: Router R2 Initial Configuration


Answer on Paper, or Maybe Test in Lab

To answer on paper, or in a text editor, just write your answers. The next post will list my suggested solution. And with this particular lab, as worded, there should be only a single correct answer.

To test in lab, you cannot use VIRL, because this lab uses serial interfaces. However, you can use Packet Tracer or real hardware. Feel free to do the lab in either environment. You can use any serial interface numbers that you want to use.

If you do implement this lab, try these show commands to get some insights into your solution:


Answers: IPv6 Standard ACL 1
Answers: MLPPP 1
By Chris September 13, 2016 09:05
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  1. Rich April 4, 09:51

    Have you actually tried this in packet tracer? I’m trying it now and I don’t have the ppp multilink commands available.

    Reply to this comment
    • certskills April 5, 06:44

      Hi Rich,
      No, I did not try this in Packet Tracer. My apologies. I’ll generally refer to PT here in the blog as a reminder to Academy folks. Sounds like MLPPP isn’t supported there. My apologies for sending you on a wild goose chase.

      Reply to this comment
      • Rich April 5, 07:42

        No worries. I was actually making up a lab for my class when I noticed the commands weren’t there. I was searching to see if I could find anyway to make it work in PT, and to make sure I wasn’t missing something. So I was on my own wild goose chase when I found the page, I just wanted to know if I was missing something.

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