GNS3 High CPU Usage

Hi Rene,

I recently subscribe here in Network lessons and I am impressed how detailed you present your topics.

Aside from that, I would like to know what kind of IOS image for GNS3 that would not eat lot of CPU performance?

Currently I have C3725 and C7200, I am doing the MPLS Topic but unfortunately I need to stop it, it literally causing me trouble when booting up those routers
even I included them into IDLE PC.

PC Specs:
Processor: AMD A10-5800k APU with Radeon HD Graphics 3.80 Ghz
RAM 8.00GB
64 Bit OS

Thanks and regards,

Hi Adrian,

I’ve been using GN3 for 4 years or so and generally find that IDLE PC values work well keeping CPU usage low. Occaisionally an existing project previously working well with existing IDLE PC values and low CPU usage changes and decides to eat up my CPU. I stop all the routers in the topology one at a time to check if one particular router causing the problem and reset the IDLE PC to rectify the problem. Try and find a value marked *, if at first there are none keep looking and eventually you will get things working efficiently. I regularly run projects with 12+ 7200 & 3600 routers on my laptop which also has 8 gb ram.

Kind regards


Hello Philip!

Thanks for sharing your experience.

I find the same thing when using GNS3, Idle PC values don’t always work. You need to reset them often as you say.

Thanks again!