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Network Troubleshooting — Network+ practice questions

Domain 5 of the CompTIA Network+ (N10-009) exam. 208 questions on this domain in the full bank — here are four free samples with answers and explanations.

Question 1 · Difficulty 3/5

A help-desk engineer has isolated a suspected misconfigured VLAN as the cause of a connectivity outage. She proposes to reconfigure the VLAN immediately because she is confident in her theory. According to the canonical seven-step troubleshooting methodology, what should she do before implementing the VLAN change? (Select the best answer.)
  1. Document the findings and actions taken
  2. Verify full system functionality and implement preventive measures
  3. Test the theory to confirm or deny it as the cause, then establish a plan of action
  4. Escalate the issue to a senior engineer immediately
Show answer & explanation

Correct answer: C

Test the theory to confirm or deny it as the cause, then establish a plan of action
After establishing a theory of probable cause (Step 2), the methodology requires testing the theory (Step 3) to confirm or deny it before proceeding. If the theory is confirmed, the engineer then establishes a plan of action (Step 4) before implementing the fix (Step 5). Skipping Steps 3 and 4 and jumping to implementation risks making an incorrect change. Documentation (Step 7) and verification (Step 6) are post-implementation steps; escalation is an option within Step 5 only after the plan is established.

Question 2 · Difficulty 3/5

A network engineer suspects that an incorrect static route is causing packet loss to a remote site. She tests her theory by examining the routing table and confirms the route is indeed misconfigured. According to the canonical seven-step troubleshooting methodology, what is the NEXT step the engineer should perform immediately after confirming the theory? (Select the best answer.)
  1. Immediately correct the static route to restore connectivity as quickly as possible
  2. Establish a plan of action to resolve the problem and identify any potential side effects
  3. Document the misconfiguration and its resolution in the change management system
  4. Verify full system functionality and implement preventive measures
Show answer & explanation

Correct answer: B

Establish a plan of action to resolve the problem and identify any potential side effects
After Step 3 (Test the Theory) confirms the suspected cause, the canonical next step is Step 4 (Establish a Plan of Action), which defines how the fix will be applied, identifies any potential side effects, and determines whether escalation is needed before changes are made. Immediately implementing the fix skips Step 4 and jumps to Step 5 (Implement the Solution or Escalate), which violates the methodology order. Documentation is Step 7 and cannot precede implementation. Verifying full functionality is Step 6 and occurs only after the solution has been implemented.

Question 3 · Difficulty 3/5

A junior network engineer resolves a DHCP scope exhaustion issue by adding a second DHCP scope and then immediately closes the trouble ticket. A senior engineer reviews the closure and flags it as incomplete. Which step or steps did the junior engineer skip that are required before closing the ticket according to the canonical seven-step troubleshooting methodology? (Select the best answer.)
  1. Re-testing the original theory and re-establishing the plan of action
  2. Verifying full system functionality with preventive measures, then documenting findings and lessons learned
  3. Duplicating the original problem and questioning users again to confirm the fix
  4. Escalating the ticket to a senior engineer and waiting for sign-off before closing
Show answer & explanation

Correct answer: B

Verifying full system functionality with preventive measures, then documenting findings and lessons learned
After implementing a solution (Step 5), the methodology requires Step 6 (Verify Full System Functionality and Implement Preventive Measures), confirming that all affected services are restored and taking steps such as adjusting lease times or monitoring thresholds to prevent recurrence, followed by Step 7 (Document Findings, Actions, Outcomes, and Lessons Learned). Closing the ticket immediately after the fix skips both of these steps. Re-testing the theory and re-establishing the plan belong to earlier steps (3 and 4) that were already completed. Duplicating the problem and questioning users again are Step 1 activities that have already occurred. Escalation is an option within Step 5 when a fix cannot be implemented, not a mandatory prerequisite to closing the ticket.

Question 4 · Difficulty 3/5

A network technician receives a trouble ticket reporting intermittent packet loss to a remote branch office. The technician checks the interface error counters, reviews syslog for recent alerts, and asks the on-site contact when the problem first appeared. Which step of the Cisco seven-step troubleshooting methodology is the technician performing? (Select the best answer.)
  1. Step 2. Establish a Theory of Probable Cause
  2. Step 1. Identify the Problem
  3. Step 3. Test the Theory to Determine Cause
  4. Step 4. Establish a Plan of Action
Show answer & explanation

Correct answer: B

Step 1. Identify the Problem
Gathering information from logs and users, identifying symptoms, and determining when the problem started are all activities explicitly listed under Step 1 (Identify the Problem). Step 2 would involve proposing a probable cause using a chosen diagnostic approach (top-down, bottom-up, or divide-and-conquer). Step 3 involves actively testing a hypothesis already formed, such as issuing ping or traceroute to confirm a suspected bad path. Step 4 involves devising a corrective plan after the root cause has been confirmed.

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