Since all the virtual devices created in GNS3 directly interact with the hardware of physical computers, memory and processor of the physical machines are also shared with GNS3 virtual devices. This means that if you run a few virtual devices on GNS3, CPU usage of physical computer will be more or less 100% even if the virtual devices are not performing any tasks. This will remarkably reduce the performances of physical computers, hence giving delayed outputs. GNS3 development team understands this and therefore it has provided with the feature named Idle PC using which you can configure the devices to utilize and share resources from physical machines only when they are working. This means that if a network topology created in GNS3 has three routers and only one is performing some task and other two are sitting idly, only the first router will share the hardware resources of physical computers and the other two virtual devices will not. It is advised that you should configure Idle PC value for every virtual device attached and involved in the topology so that you can place and work with several virtual devices at a single given time. If you want to calculate Idle PC value for any virtual device in GNS3 you need to follow the steps given below:
- Logon to the Windows on which GNS3 is installed.
- Create a new topology with a couple of virtual devices or open an existing one.
- Right click on any started device to calculate its Idle PC value
- You will be displayed with a list of values once the calculation process is completed. Some values from the list will display * sign in front of them.
- Choose any * marked value from the list and see the remarkably decreased CPU usage using Task Manager utility of Windows.