As Petr mentioned the other day, we have updated our .net file mappings to correspond with the new blueprint update for CCIE R&S v4.  Please refer to his previous post here.

If you are new to dynamips, view the tutorial Using Dynamips for CCIE Lab Preparation on a PC (How To Run Cisco IOS On Your PC)

The updated .net files can be downloaded here.  Like the previous version, the BackBone router configs are included and should automatically load when you run the .net files.

The major changes are as follows:

  • Separate .net files for Dynagen and GNS3
  • Platforms upgraded to all 3725s
  • Interface numbering now matches more closely on R1 – R6
  • Minor performance enhancements

These files were written with MacOS in mind, but can be easily modified to run on Windows and/or Linux.  From my personal experience it is very unlikely that you will get the entire topology to boot on Windows without a massive amount of hardware to back it up.

Happy Labbing!

About Brian McGahan, CCIE #8593, CCDE #2013::13:

Brian McGahan was one of the youngest engineers in the world to obtain the CCIE, having achieved his first CCIE in Routing & Switching at the age of 20 in 2002. Brian has been teaching and developing CCIE training courses for over 10 years, and has assisted thousands of engineers in obtaining their CCIE certification. When not teaching or developing new products Brian consults with large ISPs and enterprise customers in the midwest region of the United States.

Find all posts by Brian McGahan, CCIE #8593, CCDE #2013::13 | Visit Website

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44 Responses to “Updated Dynamips, Dynagen, and GNS3 Topology”

  1. You don’t by any chance have a .net file for CCIE Security?

  2. fabio says:

    Hi, in the zip file have 3 .net files, comparing the .net to GNS and the .net file to dynagen/dynamips i can see that the R6 have different connection, in the GNS .net file have S0/0 connected to BB1 s0/0 and in the other file the same router have the s0/0 connected to FRSW.

    Why that difference?

    Thanks a lot!

    • @fabio

      Functionally there’s no difference. Petr created the dynagen .net file with R6 and BB1′s connection going to the Frame Relay switch. I created the GNS3 .net file with R6 and BB1 running Frame Relay back-to-back. From R6′s side you wouldn’t know the difference between the two setups, since they are only significant to the layer 2 Frame Relay switching.

  3. @Patrick

    No, because there are too many other devices involved. You could try emulating the ASA’s with PEMU, but I haven’t really played around with it that much. Also you’d need the IPS, plus the servers for AAA and EZVPN Client. With the amount of resources and expense, I’d say it’s probably easier just to rent rack time with it.

    You could do plenty of practice on the regular router IOS for things like CBAC, ZBPF, and IPsec LAN-to-LAN

  4. Martin says:

    This link to download the .net file is not correct. It is still point to the old zip file. But the one in previous blog is correct.

  5. Yostie says:


    I’m actually working on building a GNS3 lab for the CCIE Security as at this point I have limited hardware (no ASAs, no IPS, and only a single 3560 switch). I’ve been able to boot the R1-R6, the 3 BB routers, and 2 PIX’s running 8.x code. I’m running this on a Windows 2003 Virtual machine with (2) Xeon 2.5 GHz processors and 3GB of RAM devoted to it….that setup completely maxes out the CPU on the VM.

    Anyhow, I’ve been able to mimic the two 3560′s needed by using VRF-Lite and VLANs and tying them into “clouds” in GNS3. When I get the IPS in, I’ll tie it in the same way….same with ACS (will run in a VM and tie into the GNS).

    My goal is to have it so that only the 9 routers are in GNS.

  6. Eric says:

    Nice work Brian! Thanks a lot! Definitely going to use this for future labing sessions. BTW, does anyone know how to get duplex/speed negotiation problems go away other than setting them manually on the affected interfaces?

  7. Joshep says:

    I think it would be interesting and very very useful the SP track version to GNS3 :-) )

  8. Puneet says:

    For Security you may try to use Qemu/ASA Vmware and for IPS as well you can use the VMware image available. IPS though acts funny. PIX is a good option but I personally like the VMware ASA as you can do SSL/WebVPN with it which is unavailable in PIX. For ACS as well you can run it in VMware and integrate it into GNS.

    @ Yostie: I hope you are using the BES (for Windows) for Pemu/Pix. I can do the entire lab at 60% CPU utilization and even less if I use Quemu/VMware.


  9. kaos says:

    Hmm… The (GNS3) .net file uses the image c3725-adventerprisek9-mz.124-15.T10.bin, but I was not able to find this file in Cisco’s repository, only the T9 version. Is this significantly different (apart from the idlepc value, presumably)?

  10. @kaos

    If T10 isn’t available you can use T9. It’s usually just minor bug fixes between interim releases like this. Either way you’ll have to adjust the Idle PC to get a value that works good for your setup.

  11. alex says:

    I saw that T10 needs 256 RAM but you’re configured as 128RAM. Would 128RAM configured by you not cause any problems?

    • @alex

      It really depends on how many features you have running concurrently. With 256MB RAM I was not able to get the entire topology to boot, and this was on my dual dual-core MacPro with 5GB of RAM. The image loads fine with 128MB. You’ll know if there are problems with this by the log error message MALLOC appearing (memory allocation error). All in all you should be fine unless you are taking a full view of the global BGP table into Dynamips ;)

  12. Tom says:

    Hello Brian,

    I have just downloaded the GNS files and I started it successfully it works just fine.

    But I have only one simple question, the config for switches, there is no ether channel in the configutation, does it mean that we need to configure it during the lab lessons ?

    because I see that BB routers are fully configured BGP protocol ip addresses etc…

    Shoult maybe the ether channel on the switches be configured too or ??

    I have just copied the files for example: R1.initial.config.gns3 all the files that have .gns3 at the end, is this correct ? I don`t need the files named for example: R1.initial.config ??

    Thank You and just go on You are doing very good job !!!!

    Thank You again INE team !!

    Best regards

  13. Puneet says:


    There are several issues with the GNS/Dynamips when it comes to switching. I would suggest, create a full mesh of trunks on each switch. Create SVIs and dive into the other 8 sections. Switching is one section that you can do it on racks. The racks is the best way to go for switching. I am on my 3rd CCIE and this is all talking from experience (not to mention hair pulling) when it comes to switching in GNS/Dmips. Another thing I would recommend is not creating L3 ports on the switches. You will see issues with directly connected not able to ping each other therfore best way is to create SVIs. All the best. Happy Labbing.

  14. noobie says:

    Hmz I have a problem, I am not able to run erase flash: on the switches.

    Squeeze operation may take a while. Continue? [confirm]
    %Error squeezing flash (No device available)

    Any advice?

  15. Tom says:

    Hello Puneet,

    Thank You for suggestions, hmm will see what I can do.. but the problems with rack rentals is that You are being limited to time, and if You run on to some problems where You need some time to research it than You`re out of the time for the rest…:( because the clock and time does not wait for us.. and I think it is quite expensive to use rack rentals ….

    Thank You again !!
    Best regards

  16. Dan M says:


    I was having this same problem, as well as not being able to create any VLANs. To fix the problem I changed “disk0 = 0″ to “disk0 = 64″ under the global parameters for instance 3 (where the four switches are configured). Also on a side note 12.4(15)T9 train allows you to configure VLAN’s in global config mode, no more need to use vlan database. Woohoo

  17. @noobie

    Download the .net files again, they have been updated to fix this issue with the flash filesystem size being Null.

  18. @Tom

    Also there are many features not support in the IOS switching syntax vs. the Catalyst IOS switching syntax. Either way you need to get experience with real 3550/3560 series switches before you get to the actual exam, whether you buy them and integrate them into your dynamips setup or you rent rack time.

  19. Zeynep Savas says:

    Hi Brian:
    I am very new to Dynamips. Do I need to use the GNS files with the newest .net files? I did go thru the COD on dynamips, but that does not have the GNS part. Also I am using Windows, the only change in the version 5 .net file will be the location of the image, or do I need to make other changes as well? I wanted to practice the MPLS configs that you have configured on the MPLS COD. thank you

  20. @Zeynep

    GNS3 is just a GUI that is used to launch Dynamips. It uses the same type of .net file format behind the scenes like Dynagen, with a few minor differences. Either way both Dynagen and GNS3 are just launchers for Dynamips itself.

    If you are running windows and Dynagen, the changes you will need to make are the temporary directory, where the IOS image is located, and where the initial configs are located. If there is an error with the .net file when you launch it, it will tell you specifically which line number the problem occurred on.

  21. Zeynep Savas says:

    thank you Brian.. I will try that..

  22. Roland says:

    I’ve downloaded the .net v5.0 file but what about the configurations? Should I still use v4.01 until dynamips edition of WB2 will be available? Thank you

  23. Warren Jackson says:

    Hi, I was wondering what specs you recommend for someone wanted to buy a laptop/pc that can support the entire CCIE rack of equipment for dynamips/dynagen.



  24. Warren Jackson says:

    Thanks! Is there a less expensive alternative? Someone mentioned something about running linux on a dual-core centro with 4 GB of memory.

    You will be my instructor next week in Tampa. Looking forward to the class!



    • Wow – that is AWESOME – cannot wait for that class and to meet you!

      Yes – there are dirt cheap alternatives. The key is RAM. I imagine the cheapest is to get a refurb from a place like Ubid – then hit for the max mem. Then linux install.

  25. Spyros says:

    Hi guys,

    I am new with gns3 and generally dynamips. I prepare myself for the ccie SP.

    Very quick question;

    I have a topology with 12-14 routers running 72xx ios image (c7200-k91p-mz.122-25.S15). I am currently starting bgp and the topology is based in a RR level hierarchy and I am trying to migrate that to confideration.

    When I use the command neighbor x.x.x.x shutdown so I can change the forwarding path to the other RR I can see that the bgp neighbor goes admin idle. The problem is even if the neighbor is admin idle also even if I run clear ip bgp * when I check the ip bgp table I havn’t got any routes from that neighbor but when I run a traceroute traffic goes succesfully from that neighbor.

    Are all commands run in GNS3 or not? Because even if some of them are not working on gns3 then we can’t rely on that as you may go in a diferent conclution that you should go .

    :( (((

    Please reply if you are aware as your answer is very usuable for me.

    Many thanks,

  26. Md Arif Imtiyaz says:

    Hi and Asak,

    I am able to open the full topology of v5 LAB1 and the CPU is below 30%.

    I am using Quad core with 4GB of ram and also increased the virtual memory range to 4860 – 9720.

    I have Edited the “” file and add localhost for each one of the device. the ram is 256MB.

  27. Md Arif Imtiyaz says:

    Hi the great CCIEs,

    “Brian McGahan” is my role model in professional career.
    Through you I grow
    Thank you

    I also thank all the internetwork team for helping poor people to get hands on lab using dynamips/GNS3.

    May Allah bless you all with peace of mind.

    Thank and best regards
    Md Arif Imtiyaz

  28. [...] Expert also has their own adaptation of GNS3 for their material as well. Less of a tutorial, but if you’re already up and running, just [...]

  29. Lance says:


    I’m pretty new to Dynamips. I bought the workbook version 5 Vol 2 for CCIE R&S but I don’t see any relationship between init.conf.files, .net file, diagrams and labs. Do I have to modify the .net file to look like every lab in the workbook?

    Thanks and regards !!!

  30. Mohammad Khalil says:

    Hi , where can i find volume II labs file

  31. Fabian says:

    I have downloaded the initial config files for R&S Vol2 V5, but it only has the text files – no .net files. As I think Lance is asking above, do we have to modify the original .net file to represent each lab’s topology or am I missing something? Looking at the diagrams and scenarios, they all have different topologies. I am downloading from the url below.

    • The .net file emulates the physical topology, not the logical topology in the diagrams. Just like the fact that the physical wiring never has to change for our real equipment racks, the .net file never needs to change as well.

      • kevin says:

        you say the .net file for gns3 doesnt change just like the physical cabling,,,but how do I work with the .net files to practise the vol I labs? am abit new to working with gns3…thanks

  32. mahmoud alabed says:

    Dear Brian;

    I downloaded the zip file and tried to open the GNS topology but it was always giving me that the port 6 is not connected and then the topology is not working fine so would you please let me know how can I make it work.


  33. Malith says:

    I have the same issue as Mahmoud, I also get “port 6 not connected” and nothing else work. Can you please let us know the work around for this?

  34. [...] topology .net file can be easily found in their website. The problem was, i couldn’t run it from the first instance. I had to edit with many [...]

  35. Francisca Laughridge says:

    What a timesaver! I had previously had to restart to regain VPN access. Ta.


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