Network Troubleshooting 101

Network troubleshooting is a very critical skill for IT professionals, it helps network administrators to quickly identify issues in the network, fix them and minimize downtime. As a network engineers, we spend a vast amount of my time figuring out why something that is supposed to work, doesn't or why the performance is below the expectations.

Some of the commonly used troubleshooting approaches are discussed below:

1. The Top-Down approach: This approach starts from checking end user applications (Application Layer) and moves down through the layers of the OSI(Open Systems Interconnection) model until the issue is identified.
2. The Bottom-Up approach: This approach starts from the OSI model’s physical layer and moves up toward the application layer. In this approach, you first check the physical connection, check whether the physical connections are Ok and the ports are up. Once the physical connection are confirmed Ok, you can now check the switching and routing protocols status and then the end user applications.
3. The divide-and-conquer approach:?Using this approach, you start in the middle of the OSI model’s stack (usually the network layer), and then, based on your findings, you move up or down the OSI stack.

Once you have decided the approach to use, you can follow below steps in your troubleshooting.

1. Identify the Problem

The first step in troubleshooting a network is to identify the problem. This is the most critical step in network troubleshooting. As a part of this step, you should do the following:

• Gather information?about the current state of the network using the network troubleshooting tools that you have available to you.
• Question users?on the network to learn about the errors or difficulties they have encountered.
• Identify the symptoms?of the network outage. For example, do they include complete loss of network connection? Slow behavior on the network? Is there a network-wide problem, or are the issues only being experienced by one user?
• Determine if anything has changed?in the network before the issues appeared. Is there a new piece of hardware that’s in use? Has the network taken on new users? Has there been a software update or change somewhere in the network?
• Define individual problems clearly. Sometimes a network can have multiple problems. This is the time to identify each individual issue so that your solutions to one aren’t bogged down by other unsolved problems.

2. Develop a Theory

Once you have finished gathering all the information that you can about the network issue or issues, it’s time to develop a working theory. While you’re producing your theory about the causes of the network issue, don’t be afraid to question the obvious, but remain on the lookout for more serious issues. Sometimes a network outage occurs because someone tripped on a wire or some other simple problem. However, at other times the problems might be related more complicated causes.

3. Test the Theory

Using the tools at your disposal, it’s time to test your theory. If your theory is that the network router is defective, try replacing it with another router to see if that fixes the issue. At this stage, it’s important to remember that proving your own theories wrong doesn’t mean that you’ve failed. Instead, it means that it’s time to return to step two, develop a new theory, and then find a way to test that one. Sometimes your first theory may be right, but it’s also common to go through several theories before arriving at the true cause of your network’s issues.

4. Plan of Action

Once you’ve confirmed your theory about the causes of the network issues, you’re in a position to solve them. Come up with a plan of action to address the problem. Sometimes your plan will include just one step. For example, restart the router. In other cases, your plan will be more complex and take longer, such as when you need to order a new part or roll a piece of software back to a previous version on multiple users’ computers.

5. Implement the Solution

Now that you have a plan for fixing the network, it’s time to implement it. There are some solutions that you may be able to do by yourself, while others may require cooperation from other network administrators or users. Follow the approval process before the implementation of the solution.

6. Verify System Functionality

Once you’ve implemented your solution, be sure to test the network. Make sure that the issue in question has been resolved, but also be on the lookout for other issues that may have arisen from the changes that you made to the network. As part of your verification process, make sure to consult both the network tools at your disposal as well as individual user accounts of their experiences on the network.

7. Document the Issue

If you are a network professional or an enthusiast who is around networks often, then it’s safe to say that this won’t be the last time you encounter this particular issue. Make sure to document each stage of troubleshooting the problem, including the symptoms that appeared on the network, the theory you developed, your strategy for testing the theory and the solution that you came up with to solve the issue. Even if you don’t reference this documentation, it may be helpful to another network engineer at your company in the future and could help to shorten network downtime.