How to Add Cisco IOS Router to GNS3 and GNS3 VM

If you know a lot about computer networks, you’ve probably heard of GNS3 and a Cisco IOS Router. GNS3 is a program that lets you make complicated network setups. It helps you use routers, switches, or firewall things without needing any physical equipment.

Cisco IOS is the active system that works on Cisco routers and switches. When you add these IOS images into graphical network software, you can practice on a computer. This way, it helps you get ready for Cisco’s really well-known network tests. In this article, we’ll show you how to add or import these IOS devices to the GNS3 emulator program.

How to Add Cisco IOS Router to GNS3 and GNS3 VM

The Importance of Using Cisco IOS Router in GNS3 Network Software

In programs like GNS3, you can set up different networks. This way, it helps you understand how a real network works. But the program itself doesn’t have these devices. In simple terms, the devices are not part of the program. So, you need the actual Cisco network devices’ system called IOS (Internetwork Operating System).

Extensive business networks use Cisco IOS routers. However, some don’t need a license to practice in training. With these, you can set up, design, and test networks. For example, before making a network in the real world, you can practice with IOS devices in a pretend setting. Then, you can use what you learned on actual devices following your practice.

Because of these situations, it’s crucial to add IOS devices to GNS3 software. In simple terms, whether you’re a network engineer or an IT professional, you can gain from doing this.

However, a point you should remember is Cisco’s licensing rules. You must legally have the right to use these IOS images. Cisco lets you use older versions in your virtual lab. Yet, for fancier Routing or Switching IOS versions, you’ll need a license.

Benefits of Using a Router in Virtual Topology

Adding a router to GNS3 has lots of good things about it. Cisco exams are getting more famous, and a lot of people are interested in them. So, here are the benefits of making and trying out virtual network topologies.

  1. Cost Savings

When you use a router in a virtual environment, you don’t need to buy an actual device. This helps you save money, and you don’t have to worry about taking care of the physical device. So, the GNS3 program is suitable for saving costs.

  1. Efficiency

Setting up real devices needs special knowledge. So, using routers or other things in virtual networks makes things work better. Since everything is virtual, you can effortlessly save or make changes to the setup.

  1. Flexibility

Managing changes in a real network is challenging. So, putting in, updating, or taking away routers in different parts of new network segments gives you more options.

  1. Scalability

You can make virtual topologies from easy to challenging levels. So, putting many routers in one spot adds a bit more work for your computer. In short, GNS3 makes it easy for you to make your network bigger or smaller.

  1. Network Security

Implementing current protocols in a real network is complex. You have to go back and change a lot of things, messing with a network that’s already working. So, doing these things in virtual environments is suitable for safety and doing things quickly.

Adding Cisco Router to GNS3 Emulator

Before starting the router import process, install GNS3 on your PC. Then, start the network emulator program and follow the steps to add a new device.

Step 1

In the GNS3 user interface, in the first stage, you will see the Setup Wizard window. Here, check the Run only legacy IOS on my computer option.

If you are dealing with more advanced projects, you need to select the option above and then install the GNS3 VM.

Important: If the Setup Wizard didn’t show up by itself, you can start it again from the Help menu.

Run only legacy IOS on my computer

Step 2

Once you choose Run only old IOS on my computer, click Next to keep going.

Run only old IOS on my computer

Step 3

Keep the settings that are already there in the Local Server Configuration window and click Next. But if you’re using software on your local host, you can change the port number.

Local Server Configuration

Step 4

In the Summary window, review the settings you have made and click Finish.

GNS3 Summary Window

Step 5

When the window to make a project shows up, type something in the Name part and click OK. Also, you can change the Location to save your topology in the spot you want.

Creating a New Project in GNS3

Step 6

When the New Appliance Template window opens, you will see many options. Specifically, for putting in a new Cisco Router, pick the one that says Dynamips. Now, choose the Add an IOS Router using a real IOS image (supported by Dynamips).

Add an IOS Router using a real IOS image (supported by Dynamips)

Step 7

Once you select to add an IOS Router, click OK to keep going.

Choosing to add an IOS Router

Step 8

Now, you have to choose the operating system (IOS) of a Cisco Router that you saved on your computer. So, click the Browse button to say where the image file is.

Specifying IOS Image Location

Step 9

Select a Router image that you saved on your computer, and click Open to import it.

Adding the c7200 Router

Step 10

Click Yes to open up the compressed IOS image.

Confirming IOS Uncompression

Step 11

Wait while the wizard decompresses the c7200 Router image.

Decompressing IOS Image

Step 12

After adding the IOS Router, click Next to proceed.

Verifying the Location to Add the Router

Step 13

In the window for Name and Platform, type in the model of the IOS Router you add. After that, choose the Router platform and keep going.

Configuring Name and Platform

Step 14

In the Memory screen, you can see that the default RAM value for the router is 256 MB. To run the router more efficiently on GNS3, you can increase this value. Especially if you have a powerful PC, set a higher RAM size.

Assigning an Appropriate RAM Size for the Router

Step 15

In the Network Adapters window, you can select the ports you want to add to the router from the Slot section.

For example, to add a FastEthernet port to the router, you can choose C7200-IO-FE in Slot0.

Adding a Network Adapter

Step 16

You have to set a value for Idle-PC for the router. This value can change depending on how well your computer’s processor works. So, click on Idle-PC Finder to find a good value for the 7200.

Finding Idle-PC Value for Router

Step 17

Just wait while GNS3 figures out a good Idle-PC value for the IOS router based on how your computer works.

Localhost Idle-PC Determines

Step 18

Once it finds the best IOS router value for your computer, click OK.

A Value Found for Network Device

Step 19

After you finish the Idle-PC wizard, click Finish to keep going.

Closing the Idle-PC Wizard

Step 20

Once you add in the router, look at the details in the IOS Router Templates part. For instance, in the Template Name part, you can see the model of the device you imported.

Verifying that the IOS Device is on Localhost

Creating a New Project and Testing Cisco IOS Router

Step 1

Now, take the Cisco Router you put in and drop it onto the workspace from the Devices/Router area.

Adding IOS Router to Workspace

Step 2

First, right-click to open the router’s options.

Opening the Router's Settings

Step 3

Look at the Topology Summary part to see that the router, R1, is not running right now.

Now, in GNS3, click on the listed option Start to run the router.

Running Router in GNS3

Step 4

When the device is on, the Red icon in the Topology Summary section will change to Green. Once that happens, you can open the CLI command prompt by double-clicking on the device to set it up.

Opening CLI

Step 5

As you can see in the image below, the Router you added to GNS3 is working well!

Router's CLI Screen

Step 6

For instance, type the R1# show running-config command in the Cisco Router CLI. This command will show you any configuration records made and currently running on the network device.

R1# show running-config

Adding Cisco IOS Router to Physical Network with GNS3

You can connect the Cisco Router to your desktop or laptop computer’s network. To do this, you will need to create a Cloud connection.

Additionally, you can use this method to connect the Router to the web.

Step 1

To set up the FastEthernet port of the Cisco router, double-click on it and configure it. Then, enter the following commands in the CLI command prompt. However, at this point, assign an IP address from your physical network to the corresponding port.

R1# conf t
R1(config)# interface fastethernet 0/0
R1(config-if)# ip address
R1(config-if)# no shutdown
R1# wr

Assigning an IP Address

Step 2

Now, add a Cloud device to the virtual network topology in GNS3.

Adding a Cloud Device to a Workspace

Step 3

Right-click on Cloud1 in your project.

Edit Cloud Device Settings

Step 4

Select your PC’s network adapter on the physical network to check cloud settings. For instance, you can select Wi-Fi, Ethernet, or one of the VMnet Adapter adapters.

Choosing the Wi-Fi Adapter

Step 5

Connect one end of the cable to Cloud1/Wi-Fi and the other end to the FastEthernet0/0 interface of R1.

Connecting Cloud and Router

Step 6

Click on the Start/Resume all devices button to start Cloud1 and the Router.

Operating All Devices in GNS3

Step 7

Once you have added the Router to the physical network, check the network connection by pinging from your computer. The picture below will show if the GNS3 Router can communicate with your local network.

Connecting the Host PC to the Router

Adding Router IOS to GNS3 VM (Virtual Machine) Server

In this part, we’ll add Cisco IOS into the GNS3 VM or server that’s running with VMware Workstation.

Just like importing any IOS into GNS3, you can upload them to GNS3 VM. Simply put, using a GNS3 Server helps you get better results. Also, it’s crucial because fancier ones like Cisco IOU need a VM, and it lets you keep all the IOS images you add in one central spot.

Preparing GNS3 VM (Server) for New Device

Follow these steps one after the other to add Cisco’s Router or Switch on your GNS3 server.

Step 1

Let’s assume that you have already installed the GNS3 VM. In this case, the first thing you need to do in the simulation program is to activate the GNS3 VM Server. To do this, click on Edit/Preferences again.

Edit / Preferences

Step 2

In the left section of the Preferences window, click on GNS3 VM. In the opened VM settings, check the Enable the GNS3 VM option at the top and click OK.

Enable the GNS3 VM

Step 3

In the previous step, as soon as you click OK, the GNS3 VM will start running.

Starting GNS3 VM

Step 4

You can check that the GNS3 VM is running smoothly in the Servers Summary section.

Servers Summary

Step 5

Test the connection by pinging the IP address of the GNS3 VM running in the VMware software.

Checking the IP Address of the GNS3 VM

Installing a New Network Device to the GNS3 VM

Step 1

Now, click on Edit/Preferences again to upload an IOS on the GNS3 virtual server.

Installing a New Network Device to the GNS3 VM

Step 2

In the window that opens up, you can see that the c7200 Cisco Router, which you put in before, is in the Local Server.

Now, since you will add a new device to the GNS3 VM, click on New.

Checking the Location of a Previously Added Router

Step 3

Upon clicking New, you will open the Server window. From here, this time, choose the option Run the IOS router on the GNS3 VM.

Run the IOS router on the GNS3 VM

Step 4

To add a Router or Switch, click on New Image. Then, similarly, use Browse to specify the location of the image.

Adding IOS to GNS3 Server

Step 5

Wait while the wizard copies the selected IOS image to the GNS3 VM.

Wizard Uploads IOS

Step 6

Once you copy the IOS to the server, click Next.

Checking the Location of the IOS Image

Step 7

Similarly, enter a device name for the router that will run on the GNS3 server.

Cisco c3745 Router

Step 8

To make sure the device works better on the server, change the RAM value again.

Adjusting the RAM of the IOS Image

Step 9

To set up the router’s connections, select FastEthernet or GigabitEthernet and click Next.

Adding FastEthernet Port to Router

Step 10

In the WIC Modules window, continue by adding WIC-2T.

Adding WMIC Module

Step 11

Tell the GNS3 VM router what value to use for Idle-PC.

Specifying Idle-PC for Router in the GNS3 VM

Step 12

In the final step, in IOS Router Templates, confirm that you add c3745. In the description screen, make sure that the value in the Server section says VM.

Checking that the Router is Installed in the GNS3 VM

Step 13

Close the wizard and drag the c3745 router from the devices to the workspace.

Running a Network Device from the GNS3 VM

Step 14

When you have completed everything, make sure that the GNS3 VM (Server) is running. This virtual server may be running on VMware Workstation or VirtualBox. Thus, one of these programs will be running in the background.

Now, use these commands in the CLI to test the router on the GNS3 server:

  • show ip int br
  • show version

Running Basic Commands in CLI

Our YouTube Video Tutorials

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Frequently Asked Questions About GNS3 Router (FAQ)

  1. How to use Cisco in GNS3?
To use Cisco devices in GNS3, first download and install it from the official website. Next, get the IOS file you want to use. For instance, if you are using a Router device, add it from Edit > Preferences > IOS Routers. Then, create a new project and drag the imported device into the workspace. Finally, start the device and conduct tests as if it were a physical Cisco device.
  1. Which Cisco IOS image does it support?
The Cisco device you use depends on the network emulator software. If you’re using a Switch, you need a suitable IOS file. Or, if you’re using a Router, you can get it from the Cisco website. Usually, well-known Cisco series like 2600, 3600, or 7200 work well. So, for your network plans to work the best, we suggest using the ones that work well with the software.
  1. Can I use any IOS image?
GNS3 works with lots of devices you can find in the market. But be careful about if they work well with the program and if you need a license. In short, the files on the official website work without any problems.


To sum it up, GNS3 is an excellent tool for trying out tricky network plans. That’s why lots of network engineers and people are starting to use it. In particular, it’s essential to add Cisco IOS Router devices to GNS3 because the program doesn’t have them automatically.

In the end, using IOS Routers helps you save money. It lets you use Cisco’s network devices without spending money. But, before using them in a company, make sure to check the rules about licenses.

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