Q&A on GNS3 WorkBench v8.6

I got some great questions from Rob Methven so I thought I’d answer them here in the form of a “Q&A”.

Q. I got the Etherswitches and VPCs pinging each other no problem. However, when I do a show mac-address table on the switches, the CAM table either show up as completely empty or with just the last couple of MAC addresses. Repeated show mac-address-table show that the table gradually removes the entries until it’s empty, normally within 30 seconds. I’m using the recommended IOS for the c3725 (T10), but I’ve also tried with the T14 release and observed the same behaviour.

A. This is a known problem with dynamips and has been reported on the GNS3 Forum. I’ve asked Flàvio (maintainer of dynamips) to look into it again.

Q. RE VPCS: When I load the exercises, am I right in thinking that I have to manually configure the IP addresses on the individual VPCs? I’ve done it no problem, and saved the config so I can quickly load it, but I’m just checking that I’m not doing anything wrong!

A. Some exercises will require that the IP addresses for the VPCs, others will have pre-configured exercises. To be honest, there are a couple of places where I meant to have IPs already configured but didn’t. What happens when you load a snapshot is that the contents of the snapshot’s configs directory gets copied to the current project’s configs directory. If I remembered to put the relevant startup.vpc file in the snapshot’s configs directory then the VPCs will start with the correct addresses.

Q. When I load a snapshot for a topology, I get a message saying that the IOS image can’t be found. I get an option to choose the correct image, which is invariably the same file. The only difference that I can see is the path. The images that I can use have the full paths (C:\Users\Rob\GNS3\Images\imageName.image) to the image listed in the dialog , even though it’s in my specified “Images” folder. I can fix this by editing the topology file to point to the full path, so again, it’s not a massive issue. Just wondering if I’m doing something wrong!

A. This is a real bummer – this problem was solved back in GNS3 0.8.3 and re-introduced somewhere between v0.8.3 and v0.8.6 – and since Jeremy is now busy working on GNS3 v1.0, I’m guessing there won’t ever be a real fix for this. Unfortunately going back to GNS3 v0.8.3 is NOT an option, because that version doesn’t support he Help features and the Snapshot features that GNS3 WorkBench now relies on. If you look at the toplology.net files that are supplied in the Windows/OS X version of GNS3 you will see that there is NO path specified in the

image = c3725-adventerprisek9-mz.124-15.T10.image

lines in all the exercises and snapshots. I’ve just written a script to allow a user fix this for Linux based systems (may work on OS X) but don’t have anything for Windows yet (any Windows script writers out there wanting to take a bash script and “Windoize” it please contact me!).

What you need to do is the windows equivalent of the linux command:

find . -type f -name topology.net -exec sed -i "s#c3725-adventerprisek9-mz.124-15.T10.image#C:\full\path\to\c3725-NEWIMAGE.image#" {} \;

but I don’t know if Windows has such commands.

Q. Just show me where to donate!

A. I do this to help the community. I had at one stage thought of trying to set up a link to a charity, but it got too hard. You could of course buy my book if you think it will be useful, or sign up for SlideShark using this link where you’ll get an extra 25MB free for using the link.

About RedNectar Chris Welsh

Professional IT Instructor. All things TCP/IP, Cisco or Data Centre
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11 Responses to Q&A on GNS3 WorkBench v8.6

  1. Bill Smith says:

    Hi, thanks for all your hard work on this. I’m using the full appliance download and just tried the script for the ASA .bin and it fails as it cant create the iso. How do i fix this? Also, i noticed 0.8.7 is on SF, can we update the appliance VM using those files, if so, how? Thanks, Bill.

  2. Jack Dickson says:

    Hi, first of all congratulations for your all work, lot of people are getting benefited by your work.

    Now my query – with IOS 9.2, BGP is supported on ASA but only on Cisco ASA 1000v virtual box, not physical firewalls.
    do you see any of your plan to put this feature on your project?
    this would be very beneficial if you do this.


  3. Anthony says:

    Q. When I load a snapshot for a topology, I get a message saying that the IOS image can’t be found.

    I just finished a CCENT Bootcamp and had the same issue when trying to work on an ASA lab stating the path was not correct. I was on a WIN7 64Bit system. Did anyone figure out a fix for that?

  4. Mike says:

    As a brand-new bean at using network modeling and simulation in the classroom, I have to say I’m still not quite grokking what I need to help my students do to make use of the GNS3 Workbench. This is an introductory level course on networks — “networks for managers and accountants,” you might call it — and while we’ve had limited successes with using OPNET as a Windows-based simulator platform, our Mac-using students are left in the lurch. Reading through the blogs, and watching the videos about GNS3, I’m still lost.

    What do we do to have Windows or Mac student users download the right stuff, install it, and then run a few simple labs, if we are not interested in or able to provide licensing support for things like copyrighted software or firmware (like Cisco images)?


    • GNS3 WorkBench is a Virtual Machine, so it can run on PCs or Macs (It was developed on a Mac).
      BUT… there is the problem of getting a copy of a Cisco IOS. So what are the alternatives?
      1. Cisco IUO in a VM – even more clandestine than GNS3 as far as getting images to work
      2. Cisco Packet Tracer – PC only and only be legally used by students attending a Cisco Academy course
      3. Commercial simulators – there are a few but I don’t use them and I don’t expect they’d work on OS X.
      4. Hire time on Cisco labs. These are web-based, so not OS dependant.

      If hiring lab-time is not suitable, I think your best best is GNS3 WorkBench or even the GNS3 application itself (it runs just fine on OS X). But in either case you’ll have to overcome the “IOS” problem. As an aside, (as I understand – heard it from a good inside source) the reason Cisco doesn’t make IOS freely available for GNS3 users is that there is code in every IOS that Cisco does NOT hold the copyright for – they pay royalties for its use. So to “give” IOS away to GNS3 users would require them to still pay the royalties, and keep track of every copy etc – it couldn’t be done for “free”.

      Possible corollary: If Cisco simply ignore the fact that people use IOS images for GNS3, GNS3 users get their images for free and CIsco doesn’t have to pay royalties to the copyright holders. And of course, that means that if you are using software for which the royalties have not been paid then …

  5. Snyperx says:

    I have downloaded the two files and verified the MD5 checks. I can not open the files using 7-zip. I love the GNS3 Workbench and am chomping at the bit to use it.

    How do you unzip the appliance on a Windows 7 box??

    • @Snyperx – which files did you download? Some are meant for Linux install, some for Windows – the files that end with a .tgz extension will only work on Linux. The GNS3 WorkBench Appliance is a collection of .zip/zxx files – so I would expect Windows explorer (which is what MS calls its file manager) would be able to open it. But it seems it can’t handle split files – and I’m surprised that 7-zip can’t either! Anyway – I just tested PKzip and it worked fine to open the two files for the appliance (GNS3WB86.zip and GNS3WB86.z01).

  6. Rob Methven says:

    Thank you for the speedy response!

    I had a feeling the CAM table thing would be a known bug. I didn’t even think to search the actual GNS3 forums.. probably indicative of my over-reliance on Google! Still, would’ve thought that forum page would show up as a Google result.

    I’m also making the effort to learn Powershell at the moment, so I may try to come up with a script that does what your Linux script does. Someone else would probably do a better job though.

    Anyway, thanks again! I used the link to sign up for SlideShark, and I’ll buy your book on payday (28th).

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