Hello Shivam
The truth is that there are many options that you can use for setting up a virtual lab. These are briefly discussed in the following lessons:
There are so many options and configuration parameters that we cannot cover them all within the lessons. Parameters for each solution mentioned, GNS3, VIRL and so on, can be found at their respective sites.
However, as you can see from the following post, Rene is working on updating the lessons that cover the recommended lab equipment/emulators that can be used for studying:
I hope this has been helpful!
Laz