CCIE R&S - Dynamips Possible IOS version


I start studying to the CCIE R&S and I have 2 question related to Dynamips:

1. Which best IOS platform to use ? 3725 or 3640 ?

2. which specific IOS version to use ?





  • I use the 3725 and I use that exact IOS that you have listed.  I don't really have a preference per se, but INE's topology lists that IOS version as the one that matches their study materials so I chose to stick with it.  Cisco has a neat little feature that will compare the IOS versions for you so you can see what you'd be missing.  HTH



  • hi gwilmington, may i know how you computer specification, especially your processor and memory (RAM)? I have quadcore processor with 4 gigabyte RAM, but my processor utilization still in high condition (90 - 100%). I think its becouse i used 3725 IOS that recommended by INE. I have implement the idlepc (with * in their number), but there is no different..

  • joko,

    I'm running a Q6600 Quad 2.4Ghz Intel processor with 6GB of RAM.  Are you using Linux or are you using Windows?  When I set the idlepc values for my routers I always bring the router up and leave it at the enable prompt.  I usually give them a minute or two to finish a full boot as well.  I use Linux so if you're doing it from the CLI, I just run 'top' and watch the processes to see how much processor is being used.  If you're using the GUI just bring up the Activity Monitor or whatever it's called, it escapes me right now.  I verify that the CPU is at or around 100% and then to do my 'get idlpc R1' command and select a value.  After that I check those processes to see if the utilization goes down.  Normally it drops to like 6-9% give or take.  If it doesn't, I re-run the idlepc and select another value until the CPU drops.  Just because it's a * value doesn't mean that it will work.  Try those first, and if they don't drop the CPU, then try the others.  If none work, go with another IOS.  HTH!


  • Geoff,

    You are 100% spot on. There is no "silver bullet" IOS or idle-pc. Just take the time to play around with tweaking it. It's time that's well invested.


  • I'm using windows XP professional, and i think linux was better. What kind of linux do you use? i want linux that support my additional RAM, so i can get my RAM to 6gig (XP only support to 4 gig, what a bad...)..

  • Go with whatever distro floats your boat. I run Ubuntu myself, but any distro will work just fine.

    If you are new to Linux, Ubuntu will probably be the easiest to use. It is the most Windows-like distro IMO.

    For a 64-bit version (that can do more than 4GB of RAM) you will want the image labeled AMD64. Grab this image even if you have an Intel proc. For whatever reason that's what they call 64 bit Linux.

  • I'm using Ubuntu because I'm the furthest thing from a Linux geek but I get to learn a bit about Linux and Cisco at the same time.  If you can get Linux installed and you'd like to go that route then when you're done check out this video from Blindhog.  This is what I used to setup my environment.  Once you get past all the setup pieces, which admittedly take a bit of time, it does work very well.  Post back if you have questions or need more help and I'm sure we'll be able to help you out.  GL


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