Troubleshooting LANs: Cert Guide Packet Tracer Labs ICND1 Chapter 12

By certskills May 7, 2019 09:05

Time to practice! Many people practice by reviewing and doing the examples in a book. Today’s post details some tools to help you Review, Rinse, and Repeat the examples in the ICND1 Cert Guide by using Packet Tracer. Today’s post details Chapter 12 of the book. Enjoy!

Advice before You Begin

If you haven’t read about these new Cert Guide Packet Tracer Labs that you can use with the book, take a few minutes to read the first two posts about the feature, particularly the 2nd post, which acts as a guide to using the material in each per-chapter post (like this post.) The big idea: You can learn on your own by re-creating the examples in the book, but you may be more productive in your lab time if you get a running start by using the PT files we intend to create and leave here for your use.


What’s in This Post

Intro to the Book Chapter: A brief description of the topics in that chapter of the book.

Chapter Examples and .PKT File Reference: A section that lists the examples in the chapter, the .pkt files supplied, and reminders/notes about cases in which we don’t supply all three files for any one example.

Tips and Exceptions: When we build the files, we come across items that we think might confuse you when trying the examples with PT. We write those notes in this section!


Intro to the Book Chapter

Chapter 12 of the ICND1 100-105 Official Cert Guide, “Troubleshooting Ethernet LANs”, finishes the Ethernet content as the final Chapter in Part III of the book, which is the final LAN Part in the book. The chapter revisits many of the Ethernet topics seen earlier in the book, but with a slant towards recognizing the symptoms of different types of mistakes and issues. In particular, it works through issues related to:

  • interfaces
  • switch forwarding
  • Port Security
  • VLANs and Trunks


Chapter Examples and .PKT File Reference

Download this ZIP file to get all the .pkt files for this chapter:

This table tells you what files to expect in the ZIP, and which examples happen to use interface IDs that can be exactly replicated in PT:


Example Topology File Initial Config Ending Config Exact Match of Interface IDs?
12-1 None None None N/A
12-2 Yes None Yes No
12-3 None None None N/A
12-4 Yes None Yes Yes
12-5 None None None None
12-6 Yes Yes Yes Yes
12-7 Yes Yes Yes Yes
12-8 None None None N/A
12-9 Yes None Yes Yes


Reminders: Purpose of Each Type of .PKT File

Topology File: The file contains all devices and cables in the associated figure along with any implied extra devices. The purpose: you never had to add a device or cable. It also contains a few configuration commands that do not affect the example, but help you navigate, for instance, it sets hostnames, passwords (always “cisco”), and interface descriptions.

Initial Config: The file contains everything in the Topology file, plus all configuration listed or implied by the words and figures leading up to the example. That is, it attempts to match the state of the network just before the first line of the example.

Ending Config: The file adds the configuration listed in the example to the Initial Config file – nothing more, nothing less.


Table Lists “None” or Other Strange Terms?

Some examples have all three types of PKT files, however, some Examples have no PT files, and some have a mix of fewer than three files. Here’s a reminder of why. You can check this earlier post for more background if you care to know more.

Initial Config as “None”: If the table says “yes” for the Topology and Ending config, but not the Initial config, then the Topology file has all configuration needed at the beginning of the example.

Ending Config as “None”: The Ending config will be shown as “None” when the example as printed in the book does not have any configuration commands.

All Three Files as “None”:  We do not supply .pkt files for that example.

Use x-y:  The example continues an earlier example, so use the ending config file from earlier example x-y.


Tips and Exceptions

This section lists our comments about using PT to do the examples. When we built the files, when we saw any behavior that we thought might make it more difficult to perform the example, we noted that fact so we could list it here, in case it might help you with the examples.


Examples 12-1, 12-3

We’re not supplying a PT file for these examples because they don’t have enough context. The examples are just there to show the kinds of information in some show commands.


Example 12-2

We supply the PT files for this examples but note that the one command in Example 12-2 in the book, the show interfaces interface status command, does not work the same in PT as it does in real gear, so the output in PT differs from the output in the book. In particular, in PT the duplex and speed columns do not indicate the real status of the interface – instead, they appear to show the status of the config for the interface. Consider instead trying the show interfaces interface command to see the actual status of the interface.


Example 12-4

When trying this example, note that the MAC tables do not populate in PT until you generate some traffic. Try going to the PCs in the PT topology and pinging all the other PCs. For instance, from PC1/Fred, with IP address, ping PC2/Barney ( and R1’s G0/1 (


Example 12-6, 12-7

As with Example 12-4, you need to generate some traffic to cause the fields in the show command output to populate. Try moving to the PC1 command prompt and ping to PC3 ( to generate traffic.


Example 12-8

We didn’t supply PT files because PT does not appear to support shutting down vlans, and that is the only activity in the example.


VLANs and Trunking: Cert Guide Packet Tracer Labs ICND1 Chapter 11
IP Addressing: Cert Guide PT Labs for ICND1 Chapter 17
By certskills May 7, 2019 09:05
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  1. RICHARD May 8, 09:23

    The link is downloading chapter 11 files, not chapter 12.

    Reply to this comment
    • Chris May 8, 11:05

      Hi Richard,
      Thanks for the heads up. We have corrected the link. Give it a try and let us know what you think of the examples.

      Reply to this comment
  2. Mohammed Khaliq July 17, 17:15

    Hi everyone. not sure what we need to do with the PT files. ive opened it up and it all seems to be working?
    What are we supposed to do? I mean I cant see any troubleshooting tasks.

    Please someone explain.

    Kind regards

    Reply to this comment
  3. Lolo August 13, 14:58

    I can’t find the activation code for the icnd1 100-105 book, I did find the activation code for the icnd2 book inside the CD cover, How can I ave the first code?

    Reply to this comment
    • certskills Author August 13, 17:11

      Hi Lolo,
      Couple of suggestions about your missing activation code:
      Exchange the book with your bookseller explaining that it was missing the activation code.
      You can try and reach out to the publisher and ask; they might be willing to supply a replacement. Try the “contact us” option at
      Hope this helps,

      Reply to this comment
      • Mohammed Khaliq August 13, 19:26

        Hi Lolo. I had the same problem. I didnt find the activatiion code for the ICND1 book and just left it at that. But now im going to follow the advice and see what I can get

        Reply to this comment
  4. kutay September 12, 10:45

    Dear Wendell. On PT when a duplex mismatch occurs the link between the two interfaces does NOT remain in a up/up state. Instead being disabled.

    Reply to this comment
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