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Dynamips Rocks

Posted by Jo on December 30, 2007

So Ive been working through some of the IEWB Volume I labs, mainly focusing on the BGP and Multicast topics, to familiarise myself with the Dynamips setup, and so I can start on many of the more non-core sections in the Labs. I have to say that having access to a Dynamips based rack is great. One of the things that was hindering me before was being up against the clock for my rental sessions (I know I could have booked longer sessions), but now its cool to have a rack on hand whenever I want it. It doesnt beat a real rack, but I can practice 90% of what a real rack would give me. Some of the import/export features for saving configs are fantastic and simple to use.

Yesterday afternoon I started to work on IEWB Lab 6 from the Dynamips workbook, just to get an idea of how well it would perform with some load on the routers. I have got through the core topics and finished the multicast section. There are a couple of glitches in the WB where its obvious that they have changed the full fat version for Dynamips, but these were not too difficult to work around. For the first time I could relax while doing the lab knowing that I could take a break if needed, and work on understanding the solutions a little more.

Here is what my processor looked like when I had configured all Layer 2 and IGP/BGP/Multicast sections.

Processes: 115 total, 2 running, 113 sleeping… 316 threads 11:09:34
Load Avg: 1.51, 1.58, 1.56 CPU usage: 29.3% user, 5.9% sys, 64.9% idle

Basically it flips between 28%-35% with all routing processes running – which I think is pretty good!

I am running the following IOS and idle-pc combination:


I will crack on with this lab when I have time over the rest of the holiday. Thats whats cool about Dynamips!

On another note, I now have a rack at my new job, but will be sharing it with a colleague, so this will give me a chance to practice on real hardware when I need to.


8 Responses to “Dynamips Rocks”

  1. bob said

    I’ve had occasions where I had to supply Dynamips with a hard coded MAC# on an Ethernet interface. It’s also short on some of the hardware intensive functions like VLAN filtering.

  2. ccielab said

    Yeah I know it doesnt support these features, but for 80-90% of the tasks it does the job.

  3. It works great too if you have it bridged out to real switches!

  4. ccielab said

    Yep I am sure it does, if only I had a couple of 3550 and 3560’s knocking around 🙂 Luckily I have a lab at work with 2 3550 and 2 3560’s so I can practice on those when I need to.

  5. Arden said

    Dynamips is awesome! I’m working through most of the Internetwork Expert stuff with it as well and for the vast majority its been fine. It means that I don’t have to book rack slots 24/7 and I can practice whenever the mood strikes.

    Just out of curiosity, what kind of machine are you running it on?

  6. ccielab said

    I am running it on an iMac. 20″ Intel Core 2 Duo 2.4 GHz, 2GB RAM. Once I got the right idlepc value the processor holds at around 30% with everything configured – its great.

  7. Thameem M Parambath said


    Can I use 3750 instead of 3650 as i have a couple of spare ones in my office i can use..


  8. Congratulations on passing the lab. Well Done. Just a quick question. Have you got any .net files or saved topologies which you created using Dynamips. I have bought IP BLS and need to start doing the exercise so was wondering that whether you have any saved topologies which i can use.



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