 So, the idea conveyed by our story was while troubleshooting be it a car a washing machine a computer network or an app it is made up of different subsystems and while troubleshooting you have to try to narrow it down narrow down the problem to one particular subsystem and troubleshoot. So, in case of computer networks so, what we can do is we can divide the computer network into subnetworks or say subsystems or the other approach that you can take is you can go the layer go at the layer by layer approach. So, when we look at the layer by layer approach what we can do is maybe look at the functions of what each layer is or say in the system approach try to look at what is the function of each system and then try to troubleshoot it right. At this point we have a reflection question for you please pause read the question take your time to answer and then proceed which among the following is the preferred way of troubleshooting networks option A start from physical layer and go up option B start from application layer and go down option C start from the layer which you think is faulty as some of you might have guessed all three are correct depending on the situation usually expert troubleshooters can guess the layer where the problem is and then directly start troubleshooting at that layer but for beginners this might be a little daunting as to which layer to start with so, they can either start from the physical layer and go up or application layer and go down as it is as it seems easier for them and then by practice when they troubleshoot more and more network problems they will be able to guess the layer where the problem resides and start directly troubleshooting at that layer the important part however is it is important to keep track of what are the observations that you have at different systems or different layers because that information will help you in determining the behavior and try to see which behavior is anomalous and using that you will be able to troubleshoot the system now we know that layer by layer troubleshooting is a preferred way of troubleshooting computer networks will now look in detail how to troubleshoot each layers using different tools and commands