Wireshark is another great tool. There is no better way to learn how protocols work than by observing them with Wireshark captures, and there is no better tool for obtaining those captures than GNS3. Together they make a great study pair. In this exercise, you will capture packets passing between the two routers in your Basic2Routers GNS3 project.
Step 1: Load your Basic2Routers project
Start by opening GNS3 and loading the Basic2Routers project you created earlier, if it is not already opened. By now your project should consist of two routers and two VPCS.
Make sure your routers are started, and open a console session to each of your routers. Make sure routing has converged on your routers using the show ip route and show ip protocols commands on your routers. If you have any problems, then check that your configuration matches the configuration shown in Step 5: Configure your routers in the Jumping in the deep end - a basic two router configuration section...