Learning Cisco Router Configuration with GNS3

Today I am going to tell you about GNS3. It is a Graphical network simulator. You can emulate Cisco and Juniper Routers. Knowledge of using GNS3 will be a great help for you if you are studying for certifications such as Cisco CCNA, CCNP, CCIP and CCIE as well as Juniper JNCIA, JNCIS and JNCIE. In this post I will tell you how to emulate Cisco router using GNS3.

1. GNS3 is free software and you can download it here
2. You can simply install it using double clicking the setup file you got,
3. After installing you can open GNS3 software 

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Go to  Edit --> Preferences

Then set your project saving location and Image directory at the General Tab.

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Now go to Dynamips Tab --> Click Test Sttings Button. Then you should get the message "Dynamips successfully started" as shown in next figure.

Otherwise you have a problem.

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OK. Now you have done basic steps. Now let's add Cisco router images. You can download router images here

Now go to   Edit --> IOS images and hypervisors

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Then Browse and select router image according to your need. GNS3 will automatically set RAM size for particular router image. 

Now click Save--> Close (You can set Idle PC value later,  leave it blank for now)

All right now you are almost done. Now drag a router from shown image. Use the route series which you configure the image. In my case it is C3600. (Without configuring image you can't use router)

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You can configure the interfaces of router by, Left click on router --> Configure

Then you will get a window and you can choose interfaces for your router by using slots tab.

You can start your router by, Left click on router --> Start

Now you can see R1 button on topology summary area will become green.

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But problem at this stage is your CPU utilization will become 100%. To avoid this,

Left Click on Router --> Idle PC

Then you will get a window with a drop down box. Select the value marked with star on drop down list.

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OK. That's it. Now Left click on Router --> Console.
You will get console window.

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Now we are done. Congratulations. Now you have fully working Cisco router with all functions. Best of all is it's for free. Now you can get hands on experience with Cisco routers. If you have any problem please leave a comment. In my future posts I hope to explain about Cisco Router and Switch configurations.