
From experience you can usually use a bit less RAM just fine. The minimum RAM is the amount of memory needed for IOS to work at maximum capacity with most feature configured and activated. We recommend Mainline over Technology train if you are interested on stability without the need of new features.Please see Cisco IOS Versions and Naming for more information. You will find the technology train images to contain the newest features but it may also contain the most bugs. Should I use a mainline and technology train image? # Please note that the IOSv appliance is based on IOS 15 and there are IOU (IOS on UNIX) images with IOS 15. All other platforms are now end-of-life and only support IOS 12.4. Only the c7200 series get newer IOS 15 images. Currently, the c7200 images are the only ones still available for download for those with a support contract.

IOS images are lower in cpu and memory so you can fit more of them in one topology.IOS images are usually run in Dynamips however R+Svms are housed in a virtual machine.What are the differences? Here are the major differences:

These are classified as Routing and Switching virtual machines (or R+Svms) for short. In the new GNS3 1.4, there is a way to run a second category of switches and routers. For older images, we use and maintain Dynamips an emulator dedicated to emulate some Cisco hardware.

GNS3 offers multiple ways to emulate IOS.

Install an appliance from the GNS3 Marketplace.
