Network+ (N10-009) Objective 5.0: Network Troubleshooting

The 7-Step Troubleshooting Methodology

A systematic approach to identifying and resolving network issues.

Step 1

Identify the problem

Step 2

Establish a theory of probable cause

Step 3

Test the theory to determine cause

Step 4

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

Step 5

Implement the solution or escalate as necessary

Step 6

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

Step 7

Document findings, actions, and outcomes

Step 1: Identify the problem

Gather information from users, systems, and logs.

Question users effectively (open-ended questions).
Identify symptoms and scope (who/what/when/where is affected).
Duplicate the problem if possible.
Check system logs, error messages, and monitoring tools.
Determine if anything has changed recently.

Step 2: Establish a theory of probable cause

Formulate potential reasons for the identified symptoms.

Start with the most obvious or simplest explanations first.
Consider the OSI model (start bottom-up or top-down).
List all possible causes based on the symptoms.
Prioritize theories based on likelihood.

Step 3: Test the theory to determine cause

Systematically test your prioritized theories.

Test one theory at a time.
Determine the specific steps needed to test the theory.
If the theory is confirmed, proceed to the next step.
If the theory is disproven, establish a new theory or re-evaluate symptoms.
Escalate if necessary after exhausting initial theories.

Step 4: Establish a plan of action to resolve the problem and identify potential effects

Outline the steps needed to fix the issue and consider consequences.

Define specific actions required.
Identify necessary resources (hardware, software, personnel).
Consider potential impacts of the solution (downtime, configuration changes).
Develop a rollback plan in case the fix causes further issues.
Obtain necessary approvals if required.

Step 5: Implement the solution or escalate as necessary

Execute the plan of action.

Perform the steps outlined in the plan.
Make changes methodically.
If the problem exceeds your expertise or authorization, escalate to the appropriate team.
Communicate progress to stakeholders.

Step 6: Verify full system functionality and, if applicable, implement preventative measures

Confirm the problem is resolved and prevent recurrence.

Test all related system functions, not just the specific symptom.
Have the user confirm the issue is resolved.
Monitor the system for a period to ensure stability.
Identify and implement measures to prevent the problem from happening again (e.g., updates, configuration changes, monitoring).

Step 7: Document findings, actions, and outcomes

Record the entire troubleshooting process.

Document symptoms, diagnosed cause, steps taken, and final resolution.
Include dates, times, and personnel involved.
Update knowledge base articles or network diagrams.
This aids future troubleshooting and demonstrates work performed.

Exam Tip: Methodology Order

Remember the order of the troubleshooting steps for the exam. The CompTIA Network+ often includes scenario questions where you need to identify which step comes next in the process.

Applying the Methodology

Example of how to apply the 7-step process to a real network issue.

Scenario: Users can't access a file server

1. Identify the problem

Interview affected users, collect information about when it started, and which users/systems are affected. Verify multiple users can't connect.

2. Establish a theory

Possible causes: network connectivity issue, server down, service stopped, permissions issue, or DNS problem.

3. Test the theory

Ping the server, check if server is powered on, verify network services are running, test DNS resolution.

Theory confirmed:

Server is running but file sharing service has stopped.

Follow remaining steps: create a plan to restart the service, implement solution, verify full functionality, and document findings.

Interactive Troubleshooting Scenario

Apply the 7-step methodology to solve a common network issue.

Network Connectivity Issue

Multiple users report they cannot connect to the internet. You arrive at their office area to investigate.

What would you do next?

Exam Preparation Tip

Memorize the 7-step troubleshooting methodology in order. For common problems, understand the symptoms, likely causes, and primary tools used for diagnosis (e.g., no connectivity - check physical layer, check IP config with `ipconfig`, test reachability with `ping`). Know the primary function of each command-line tool (ping, ipconfig, tracert, netstat, nslookup, arp) and hardware tool (cable tester, punchdown tool, tone generator). Understand how to approach wireless issues (signal, interference, configuration).