GNS3

What is GNS3?

GNS3 is a graphical network simulator that allows you to design complex network topologies. You may run simulations or configure devices ranging from simple workstations to powerful Cisco routers. It is based on Dynamips, Pemu/Qemu and Dynagen.
  

Dynamips

 Dynamips is an emulator computer program that was written to emulate Cisco routers. It has been created by Christophe Fillot who started his work in August 2005. ... Dynamips emulates Cisco platforms 1700, 2600, 2691, 3600, 3725, 3745, and 7200.

QEMU (short for Quick Emulator)

 It is a free and open-source hosted hypervisor/kernal that performs hardware virtualization .

Qemu is like same as Virtual Box,Vmware workstation,Vmvare player etc. A guest operating system runs as a process on the host.

 We can load CISCO ASA,JUN OS,IDS etc using QEMU

Dynagen.   

Dynagen is a text-based front end for Dynamips, which uses the “Hypervisor” mode for communication with Dynamips. Dynagen simplifies building and working with virtual networks.Provides a management CLI for listing devices, starting, stopping, reloading, suspending, resuming, and connecting to the consoles of virtual routers. 

  WinPcap

Windcap required for GNS3 to communicate with real networks through a physical network internal controller. Make sure that the "Automatically start the WinPcap driver at boot time" check box is ticked.

Architecture

GNS3 consists of two software components:

1. The GNS3-all-in-one software (GUI)
2. The GNS3 virtual machine (VM)

Install the all-in-one software on your local PC (Windows, MAC, Linux) and and create your topologies using this software. This is what you usually see show in screenshots such as the following:
https://www.gns3.com/software/download

 

The GNS3 virtual machine (VM) :you have to download GNS3 VM image and need to import/install in any of the VM hosting platform like VMware Player or virtual box.For doing switching labs am recommending VM L2 IOU images

Advantages:

• Free software
• Open Source software
• No monthly or yearly license fees
• No limitation on number of devices supported (only limitation is your hardware: CPU and memory)
• Supports multiple switching options (ESW16 Etherswitch, IOU/IOL Layer 2 images, VIRL IOSvL2):
• Supports all VIRL images (IOSv, IOSvL2, IOS-XRv, CSR1000v, NX-OSv, ASAv)
• Supports multi vendor environments
• Can be run with or without hypervisors
• Supports both free and paid hypervisors (Virtualbox, VMware workstation, VMware player, ESXi, Fusion)
• Downloadable, free, pre-configured and optimized appliances available to simplify deployment
• Native support for Linux without the need for need for additional virtualization software
• Software from multiple vendors freely available
• Large and active community (800,000+ members)

 

From where we will get GNS3 

We have Version 2.0.3 as the latest one available now.

Link for gns3:https://www.gns3.com/software

All others versions :https://sourceforge.net/projects/gns-3/files/GNS3/

Best performed GNS3  versions for me :0.8.7 and 1.2.3

 

 Requirement for GNS3 Installation

GNS3 supports the following operating systems:Windows xp,7,8,10,Windows server 2012,2016,Linux,ubundu.

Memory :Minimum 1 gb for better performance

HDD:min 1 gb