GNS3 (Graphical Network Simulator-3) is a Cisco equipment simulator. This tool allows you to install the actual Cisco IOS and use them in full simulation on a single computer.

GNS3 allows you to run and use a virtual Cisco router on your computer. However, GNS3 itself does not contain IOS images of Cisco devices. These images can be obtained from the Cisco website or other sources.

This simulator software is widely used by the system and network engineers to prepare for Cisco CCNA, CCNP, CCIP, or CCIE certificates.

For me, I use this software to test the IOS features. For example, it is the most ideal software to perform OSPF (redistribution, filtering, authentication) tests.

In other words, a virtual unit (Routers, Switches, Hosts, among other things) allows us to observe the behavior of sending and receiving information over a small LAN or something over the network.

Cisco network simulator program to allow full simulation of two main components:

• Dynamips is an IOS image emulator that can initiate IOS binary images from Cisco Systems.
• Dynagen, a text-mode interface for Dynamips.

GNS3 is free software that runs on multiple platforms, including Windows, Linux, and macOS X.

Supported Platforms

Currently supported and commonly used Router models are:

• C2600 (2610, 2611, 2620, 2621, 2610X Series, 2620/21/50/51/XM, 2691)
• C3600 (3620, 3640, 3660)
• C3700 (3725, 3745)
• C7200

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