Network Troubleshooting Methodology

Troubleshooting Methodology

Reliable service and fast resolution of the problem are expected by the users and user satisfaction is of utmost importance. Thus, ensuring high network availability is the role of network administrators. This section shows the implication of network knowledge in a coherent way to resolve network problem.

The task o inf troubleshooting becomes more complex with the number of devices and scope of infrastructure. Nevertheless, there is set of core troubleshooting steps to troubleshoot a network irrespective of its size and scope

CompTIA Network+ troubleshooting methodology comprises the steps discussed in detail in the following sections:

Identify the Problem

In the first step of the troubleshooting methodology, the main objective of the CompTIA Network+ expert is to find out and state the problem or an issue. In this stage, the focus is on the information gathering, questioning users, identifying symptoms, determining if anything has changed and asking multiple users individually. The various steps involved in this stage are:

Gather information: In order to find the underlying cause of a problem the troubleshooter is required to collect information using network maintenance tools or interviewing users. Further, he/she should define the scope of the problem which helps in identifying the source of the problem. For example, if the incident has affected a single system or all the systems on the entire floor. The troubleshooter should also check the additional sources of information such as logs maintained by other technicians.

Question users: In order to identify a problem, a user should be asked pertinent questions to gather specific information regarding the issue. Further, it should not be assumed that a user has caused the problem. Further ahead, a user can be asked to elaborate on the problem. For instance, if the user says he cannot connect to a remote server. Then, he can be questioned whether he can ping himself. Thus, if the user is unable to ping, then there could be a problem with the network adapter in the system. A user can be asked questions such as:

  • When did the user first experience the problem?
  • What are the errors messages being displayed on the screen?
  • Is any other user also experiencing the same problem?

Duplicate the problem, if possible: Then, the expert should try to duplicate the problem on the user’s system or a test system. Sometimes duplicating a problem helps in determining the cause of the problem.

Identify symptoms: The expert is required to identify the actual symptoms of the problem. He/she can check system logs to find the problem. It needs to be confirmed whether the problem is local to the computer or a networking issue. Further, an issue might have been caused by the recent changes to a computer system. There may be numerous reasons for a system failure. Thus, to resolve a problem it should be divided into smaller parts and each part approached independently. This further helps in deciding and following a specific sequence to solve a problem.

Determine if anything has changed: In order to find more clues about the problem and to identify if the user has made any changes to the system, the expert is required to ask user questions such as:

  • What was the user trying to access or run?
  • What are the recent changes made to the system?
  • Is it working on another computer system?

These questions help in finding answers if the system was in working condition before and it stopped working after a user made any changes. It might be possible that the user may have installed a new application, applied patches or updates, or performed other changes on the computer.

Approach multiple problems individually: Sometimes, while resolving one issue, the expert may find multiple problems. For instance, a user facing connectivity problem could be a result of incorrect IP configuration. Further, while solving this problem, the expert also finds that along with incorrect IP address configuration, the system is also not configured to receive proper maintenance updates or different proxy server being set up on the system. Then, in that case the expert is required to handle and resolve each of the problems.

Establish a theory of probable cause

In this stage, hypotheses are made to arrive at a probable cause of the problem. Further, possible causes are analysed to establish whether a problem is software or hardware related and accordingly steps are framed to approach an issue. For example, if the user is unable to connect to a server, then the problem could be with the adapter or the Internet connection and a simple resolution is to connect to a different server, ping its IP address and check the connection.

Thus, when the problem has been isolated test should be performed to confirm the hypothesis. Further, the probable solution might require contacting the vendor of the hardware for any assistance. However, if the exact cause of the problem remains unidentifiable, it should be escalated to a higher level. The various steps involved in this stage are:

Question the obvious: While creating a possible theory, an expert is required to question the obvious steps. For example, to connect a system to a network, the first step is to connect the cable to the Ethernet. So, ensure that the cable is inserted properly. Follow the obvious steps to find out what should happen and where is the point of failure.

Consider multiple approaches: Problem can be easily resolved if multiple approaches are used. For example, to troubleshoot a problem, the top-to-bottom and bottom-to-top OSI model can be followed. For instance, when a user is not able to access a remote server, the steps of troubleshoot using bottom-to-top OSI model can be:

  • Check if the Ethernet cable is properly established.
  • Check if IP address configurations are correct.
  • Check if the system corrects IP configurations from the DHCP server.
  • Check if the system is pinging a local IP address in the network.
  • Check if the system is pinging the local gateway.
  • Check if another system is able to ping a remote server to find if the remote server is up.

In the preceding steps first the problem at the lowest layer was checked and then the problems related to the higher layer were approached. Thus, if the problem is resolved in this manner, the expert can easily go back and follow a different approach.

Divide and conquer: In this step, the expert can divide the problem into various layers and then approach towards its solution. For example, an expert can directly ping the local gateway of the network to check if the system can connect to the network. Thus, if the system is pinging correctly, then there is no problem with the configuration of the system. Further, there are high chances that the problem lies with the router or remote server. On the other hand, if the system cannot ping the local gateway correctly, then the problem is with the system and the expert can work towards finding a solution for the issue.


Test the theory to determine the cause

In this stage, when the theory of probable cause is established, the expert is required to confirm the theory. If the theory is, confirmed, then he/she is required to decide the next steps to resolve the problem. But there are also chances that the theory might not work than he/she is required to re-establish a new theory or escalate the problem. The two conditions of this stage are:

Once the theory is confirmed, determine the next step to resolve the problem: After establishing a theory which might be the probable causes for an issue it needs to be confirmed by testing each solution and the related hardware and software components. Sometimes, it might be a simple problem such as:

  • Ethernet cable is disconnected
  • Router is turned off or the adapter disabled
  • Expansion cards mid chips are not partially inserted

Also, a simple solution like restarting a computer, which clears its memory may resolve the issue. Further, if restarting does not solve the problem, then a system can be completely shut down and rebooted.

If the theory is not confirmed, re-establish a new theory or escalate: In this stage, if a theory proposed by an expert is incorrect, then he/she is required to set up a new theory or can escalate the problem. Escalation means asking or referring the problem to a senior expert. Thus an expert can escalate the problem if it is not in his/her scope is unable to troubleshoot.

Establish a plan of action to resolve the Problem and identify potential effects

Attar testing the solution, there can be three possible outcomes:

If the problem is not fixed, then trying another solution

If the problem is fixed, than implementing the solution

If everything  is working fine, then documenting the solution

At times, a single problem can effect multiple computer on network for example, due to incorrect configuration of the file server users may be unable to access the file server on the computer. Thus, in this case, the possible solution can be making changes to the file server. Further, lithe DHCP server is misconfigured and the server is providing a wrong default gateway to all the computers, then the possible solution may be to correct the configuration on the server.

Implement the solution or escalate as necessary

After preparing a plan of action, the plan needs to be implemented. While implementing a solution an IT person may encounter several problems which do not lie under his domain. Under this condition, an issue should be forwarded to a senior administrator to complete the process of implementation. Further, if a team is working on a particular issue then the problem should be discussed with all the team members.

Verify full system functionality and, if applicable, implement preventive measures

While verifying the full functionality of a system it should be checked that the system is functioning properly, and all the issues have been resolved. On occasion, it happens that a solution to one problem can create some other problems in the system. For example, if you assign a static IP. Address to a computer, it may create problems for other computers in the .network. As it might be possible that the DHCP server has already assigned that IP address to another computer. Further, this may lead to an IP address conflict.

Thus, while implementing a solution it should be ensured that it does not create any other issue and if necessary certain preventive measure. Can also be adopted. For instance, if the error is user-generated, than it should be ensure as a preventive measure that the user understand the problem. So that he does not repeat the same error in the working on the system. For example, if the user has disabled the Ethernet adapter by mistake, then it should be ensured that the user does not disable the adapter again.


Document findings, actions and outcomes

Documenting a solution for a Kohler’) considered a good practice. As similar problems keep recurring and documenting its solution can ensure a speedy resolution. Further, several other users can benefit from an experience of one user if a solution has been properly documented.

Further ahead, documentation should be saved in the form of a log. Thus, if someone makes a change or fixes something, it automatically is stored in the logs. In addition, logs help in saving time, identifying the problem, detecting a recurring problem and finding a permanent solution to that problem.

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