Problem Resolution Model Approach

The problem resolution model contains a set of nine well-defined steps that enable you to identify a problem and efficiently implement a solution with minimum effort and time. Using this model, the entire task is divided into a series of manageable steps. The problem resolution model is a Cisco-proprietary solution used for troubleshooting networks. This model divides the troubleshooting process into the following steps:

Problem definition
Facts collection
Consideration of possibilities
Action plan definition
Action plan implementation
Observe and review findings
Review problem solving cycle
Isolation of error
Resolve the problem

Figure 1.8: Cisco’s problem resolution model.

Problem Definition

In this step, you ascertain the domain where the problem exists and define the cause and scope of the problem. This enables you to create an action plan in the subsequent steps of the Cisco problem resolution model. Figure 1.9 depicts a scenario in which Intranet A and Intranet B are connected over a high-speed backbone. Computer 1 and Computer 2 are part of Intranet A, and Computer 3 and Computer 4 are a part of Intranet B.

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Figure 1.9: Diagram of an internetwork.

In Figure 1.9, a problem arises when Computer 1 is unable to send data to Computer 4 due to a break in any of the connection links between: Computer 1 and Intranet A, Intranet A and Intranet B, or Computer 4 and Intranet B. As a result, Computer 1 cannot establish a link to Computer 4. To resolve the problem, you need to gather some facts pertaining to the problem. The output of problem definition serves as an input to the next step: facts collection.

Facts Collection

The problem resolution model initiates a fact collection process after the completion of problem definition. In this process, you gather all information pertaining to the problem, using the following parameters:

Possible causes
Logs of the events before and after the problem occurred
Scope of the problem to estimate the probable effect on other areas of the network

Taking the example of Intranets A and B, following are some basic facts that enable an optimal process of resolving the problem:

Is Computer 1 able to link to Computer 2?
Is Computer 3 able to link to Computer 4?
Is Intranet A able to link to Intranet B?

Consideration of Possibilities

After you have collected all the facts, you analyze and select the one relevant to the problem. Using the example of Intranets A and B, you can list the different possibilities, such as the link between the Intranets or the links between hosts of an Intranet are dysfunctional . This step is useful to iteratively eliminate the possibilities that are not relevant to the problem in contention .

Action Plan Definition

In this stage, you need to document the steps to be taken to solve the problem. Here, you select the most likely cause for the problem and create an action plan. An action plan contains a systematic procedure that lists the steps for resolving the error that has occurred. This step entails all the inputs of the facts collection step and consideration of possibilities. For example, with Intranets A and B, the probability of a breakdown of the link between the two Intranets is the highest.

Note

The action plan should not be defined in such a way that its implementation leads to other cascading problems. When defining the action plan, you should perform an appropriate risk analysis.

Action Plan Implementation

Action plan implementation is a step-by-step process of rectifying the problem by making changes. These changes are implemented such that any repercussions to a particular change can be easily traced. In addition, the actions performed for resolving the problem should be reversible in case of any subsequent problem. You also need to take incremental backups and maintain a log of the entire implementation process.

Observe and Review Findings

In this step, the final solution implemented for the problem is observed and reviewed. You need to analyze the changes done during implementation, any additional impact on the system due to the implementation of the action plan, and the alternate solutions considered during the definition step.

This step is a review process for the previous steps of the model. The facts collection at the second step should be reviewed. You need to ensure that the information gathered for solving the problem is optimally utilized.

Review Problem Solving Cycle

The process of reviewing all the steps implemented and observing the results so far is called review problem solving cycle . The objective of this step is to distinctly identify the actual causes for the problem. In addition, it enables you to enhance the problem definition model and eliminate irrelevant changes.

Isolation of Error

This step isolates the error occurring in the system. Based on the inputs from the previous steps, you need to isolate the actual problem or error from the system. You also need to ensure that the entire process is logged and the error is timestamped to serve as a reference, in case the error occurs again.

Resolve the Problem

In this step, the identified problem is resolved using the solutions identified in the previous steps. After the problem is resolved, it is tested to confirm that the identified problem is rectified and the network is working properly. Besides testing the rectified problem, the entire process of resolving the problem is documented for future reference.

Case Study

Davis has recently joined Blue Moon Computers as an assistant network administrator. Blue Moon Computers deals with manufacturing hardware devices such as monitors , printers, and scanners . The head office of Blue Moon Computers is situated at Denver, with its branches in Chicago and New York. Each branch office has an individual network, which is connected to the head office, where these networks are maintained and administered.

James, an employee of the Chicago branch, contacts Davis and tells him that he is unable to transfer a file to the New York branch. Davis consults his supervisor, Norman, who suggests that Davis collect all the relevant information from James, identify the possible causes, and resolve the problem.

When Davis explores the causes of the problem, he discovers that a connection could not be established between Host B of the Chicago network and Host S of the New York network. After defining the problem, Davis should:

Collect facts and details about the possible causes of the problem. The causes could be that the router is overloaded and may not be taking any more requests to transfer data, or a connection is being established but the data being transmitted is corrupted during transmission.
Identify the most likely cause of the problem. In this case, the most likely cause of the problem is that the router is overloaded and is unable to take any more requests to establish a connection and transfer data.
Design an action plan to provide a solution to the problem. A probable solution could be that a priority algorithm must be applied to all the requests being sent to the router. This enables the router to prioritize the routing of data.
Implement a priority algorithm, such as the round- robin algorithm to prioritize the requests.
Review the results of implementing the action plan.
Identify whether there are any other related problems that have occurred due to the implementation of the priority algorithm.

If reviewing the results does not indicate any other errors or problems, the problem being solved is isolated, and its solution process is documented for future reference.

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Anand V., Chakrabarty K.

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