Q1. What does a TDR (Time-Domain Reflectometer) help identify?
- A.Network congestion
- B.Cable faults✓ Correct
- C.IP conflicts
- D.DNS issues
Explanation: TDRs locate cable breaks or impedance mismatches by measuring signal reflections. Learn more.
CompTIA Network+ Practice Questions: Network Troubleshooting
34 free, exam-style CompTIA Network+ (N10-009) practice questions covering Network Troubleshooting. Each question shows the correct answer and a clear explanation. Ready for the real thing? Take the full timed quiz below.
Q2. What does the 'tracert' command use to map network paths?
- A.TCP SYN packets
- B.ICMP echo requests
- C.UDP packets with TTL increments✓ Correct
- D.ARP requests
Explanation: tracert (Windows) uses UDP packets with increasing TTL values to trace routes. Learn more.
Q3. What does a high number of CRC errors indicate?
- A.Network congestion
- B.Cable faults✓ Correct
- C.DNS issues
- D.Firmware bugs
Explanation: CRC errors suggest physical layer issues like damaged cables or connectors. Learn more.
Q4. Which tool would you use to test DNS resolution?
- A.ping
- B.nslookup✓ Correct
- C.tracert
- D.netstat
Explanation: nslookup queries DNS servers to troubleshoot name resolution. Learn more.
Q5. What is the purpose of a loopback address?
- A.Test network interface functionality✓ Correct
- B.Route traffic between VLANs
- C.Assign default gateways
- D.Reserve IP addresses for servers
Explanation: 127.0.0.1 (IPv4) or ::1 (IPv6) allows self-testing of network interfaces. Learn more.
Q6. What does a cable certifier test that a simple tester doesn't?
- A.Continuity
- B.Cable length
- C.Performance to specification✓ Correct
- D.Connector type
Explanation: Certifiers verify cables meet Cat 5e/6/6a performance standards. Learn more.
Q7. What does the 'netstat -ano' command display?
- A.ARP cache
- B.Routing table
- C.All network connections with PIDs✓ Correct
- D.DNS records
Explanation: -a shows all connections, -n displays numerical addresses, -o shows process IDs. Learn more.
Q8. Which tool captures network traffic for analysis?
- A.ping
- B.traceroute
- C.Wireshark✓ Correct
- D.nmap
Explanation: Wireshark is a packet sniffer for deep network analysis. Learn more.
Q9. What does a high latency value indicate?
- A.Low bandwidth
- B.Network congestion
- C.Long delay in data delivery✓ Correct
- D.Packet loss
Explanation: Latency measures time delay in data transmission (measured in milliseconds). Learn more.
Q10. What does the 'show interface' command display on a switch?
- A.Routing table
- B.MAC address table
- C.Port status and statistics✓ Correct
- D.ARP cache
Explanation: Displays interface details like speed, duplex, errors, and packet counters. Learn more.
Q11. Which tool measures signal loss in fiber optic cables?
- A.TDR
- B.OTDR✓ Correct
- C.Spectrum analyzer
- D.Cable certifier
Explanation: An OTDR (Optical Time-Domain Reflectometer) is used to detect faults, splices, and breaks in fiber optic cables by measuring reflected light signals. Learn more.
Q12. What does the 'ipconfig /flushdns' command accomplish?
- A.Clear ARP cache
- B.Reset TCP/IP stack
- C.Clear DNS resolver cache✓ Correct
- D.Release DHCP lease
Explanation: This command clears the local DNS resolver cache, which can help resolve name resolution issues caused by stale or incorrect DNS records. Learn more.
Q13. What does the 'tcpdump' command do in Linux?
- A.Test TCP connections
- B.Capture network packets✓ Correct
- C.Display routing tables
- D.Manage firewall rules
Explanation: 'tcpdump' is a packet analyzer that captures and displays packets for real-time network traffic analysis, useful for diagnosing network issues. Learn more.
Q14. What is the primary purpose of MTR (My TraceRoute)?
- A.Continuous path analysis✓ Correct
- B.Bandwidth measurement
- C.Packet capture
- D.DNS validation
Explanation: MTR (My TraceRoute) provides a continuous stream of route and latency information to diagnose path and performance issues across a network, combining traceroute and ping functionalities. Learn more.
Q15. What is the primary purpose of a network tap?
- A.Monitor traffic✓ Correct
- B.Boost signals
- C.Filter packets
- D.Route traffic
Explanation: Network taps provide passive traffic monitoring capabilities. Learn more.
Q16. A user reports they can access local network resources but cannot browse the internet. Pinging external IP addresses fails, but internal pings succeed. Which network configuration setting on the user's workstation is MOST likely misconfigured or missing?
- A.IP address
- B.Subnet mask
- C.Default gateway✓ Correct
- D.DNS server
Explanation: The default gateway is the router address that a host uses to send traffic to destinations outside its local network. If it's missing or incorrect, internet access will fail, but local network communication will work. Learn more.
Q17. Which Windows command-line utility would a technician use to display all active TCP connections, listening ports, Ethernet statistics, and the IP routing table?
- A.ipconfig
- B.tracert
- C.ping
- D.netstat✓ Correct
Explanation: `netstat` (network statistics) is a versatile command that can display various network information. For example, `netstat -ano` shows active connections and listening ports with associated process IDs, `netstat -e` shows Ethernet statistics, and `netstat -r` shows the routing table. Learn more.
Q18. According to CompTIA's troubleshooting methodology, what is the IMMEDIATE next step after identifying the problem by questioning the user and identifying changes?
- A.Establish a plan of action to resolve the problem.
- B.Test the theory to determine the cause.
- C.Establish a theory of probable cause.✓ Correct
- D.Document findings, actions, and outcomes.
Explanation: After gathering information to identify the problem, the next step in the CompTIA methodology is to establish a theory of probable cause (or causes) based on the symptoms and your knowledge. Learn more.
Q19. A network administrator observes that a specific server's network interface is experiencing a high number of collisions. This server is connected to an older network hub. What is the MOST likely solution to reduce collisions?
- A.Replace the server's NIC.
- B.Replace the network hub with a switch.✓ Correct
- C.Change the server's IP address.
- D.Install a firewall in front of the server.
Explanation: Hubs operate in a single collision domain, meaning collisions are common. Replacing the hub with a switch, which creates separate collision domains for each port (in full-duplex mode), will eliminate collisions for the server. Learn more.
Q20. A network technician wants to send a continuous stream of ICMP echo requests to a specific IP address to monitor connectivity over time. Which parameter is commonly used with the `ping` command in Windows to achieve this?
- A.-c (count)
- B.-t (continuous)✓ Correct
- C.-l (size)
- D.-n (number)
Explanation: The `-t` parameter with the `ping` command in Windows sends echo requests to the specified host continuously until it is manually stopped (e.g., by pressing Ctrl+C). This is useful for observing intermittent connectivity issues. Learn more.
Q21. A network technician uses a cable tester and discovers that a newly terminated UTP cable has a "split pair" fault. What is the MOST likely performance consequence of this wiring error?
- A.The cable will not be able to provide Power over Ethernet (PoE) to connected devices.
- B.The cable will experience excessive crosstalk and significantly degraded performance, especially at Gigabit Ethernet speeds or higher.✓ Correct
- C.The cable will only be able to operate in half-duplex mode, reducing overall throughput.
- D.The cable will appear as completely disconnected to the network interface card (NIC).
Explanation: A split pair occurs when wires from two different twisted pairs are incorrectly crossed (e.g., one wire from pair 1-2 is swapped with one wire from pair 3-6, but the pairs themselves are still connected to the correct pins). While it might show continuity, this destroys the carefully balanced nature of the twisted pairs, leading to high levels of Near-End Crosstalk (NEXT) and poor performance, especially for high-speed data transmission. Learn more.
Q22. According to CompTIA's troubleshooting methodology, when is it generally appropriate for a technician to escalate a problem?
- A.Immediately after identifying the problem and before attempting any fixes.
- B.After the first attempt to fix the problem fails, regardless of complexity.
- C.When the problem is outside the technician's expertise, authorization level, or if a solution cannot be found within a reasonable timeframe despite diligent effort.✓ Correct
- D.Only after all possible solutions have been attempted and documented over several days.
Explanation: Escalation is a crucial step when a technician determines they cannot resolve an issue effectively. This could be due to lack of knowledge, skills, necessary permissions, or if the problem's scope or time constraints require higher-level intervention to meet service level agreements (SLAs). Learn more.
Q23. A network technician observes that the link status LED indicator for a switch port, to which a user's PC is connected, is completely off (not lit). What is the MOST likely implication of this observation?
- A.The port is operating at its maximum configured speed (e.g., 1 Gbps).
- B.There is excessive network traffic or a broadcast storm on that port.
- C.There is no physical layer link detected on the port; it's likely disconnected or there's a cable/NIC fault.✓ Correct
- D.The port has been administratively shut down by a network administrator.
Explanation: An unlit link status LED on a switch port typically indicates that no Layer 1 (physical) link is established. This could be due to a disconnected cable, a faulty cable, a problem with the NIC in the connected PC, the PC being powered off, or an issue with the switch port itself. While an administratively shut down port also shows no link, the most common initial assumption for an unlit LED is a physical connectivity problem. Learn more.
Q24. Users in a densely populated office environment are complaining of slow and unreliable Wi-Fi performance, particularly on the 2.4 GHz band. A wireless site survey reveals that many nearby access points are configured on adjacent or overlapping channels (e.g., channels 1, 2, 3, 4, 5). This is a common example of what type of wireless problem?
- A.SSID mismatch causing client confusion.
- B.Incorrect encryption type (e.g., WEP instead of WPA2).
- C.Co-channel interference (CCI) and/or Adjacent-channel interference (ACI).✓ Correct
- D.Insufficient DHCP lease scope leading to IP address exhaustion.
Explanation: When multiple Wi-Fi access points in close proximity operate on the same (co-channel) or nearby overlapping (adjacent-channel) frequencies in the limited 2.4 GHz band, their signals interfere with each other. This interference degrades signal quality, reduces throughput, and can lead to unreliable connections. Proper channel planning using non-overlapping channels (e.g., 1, 6, 11 in North America) is crucial to mitigate this. Learn more.
Q25. A network technician needs to diagnose packet loss and latency issues occurring at specific hops along the path to a remote server. Which Windows command-line utility sends a series of echo requests to each router between the source and destination and computes statistics for each hop over a period of time?
- A.ipconfig
- B.netstat
- C.pathping✓ Correct
- D.arp
Explanation: `pathping` is a Windows utility that combines features of `ping` and `tracert`. It first traces the route to the destination and then sends pings to each hop along the path for a period of time to gather statistics on packet loss and latency at each intermediate router. This helps pinpoint where network problems are occurring. Learn more.
Q26. In the CompTIA troubleshooting methodology, what is the next step after 'Establishing a theory of probable cause'?
- A.Document findings
- B.Establish a plan of action
- C.Test the theory to determine the cause✓ Correct
- D.Verify full system functionality
Explanation: Once a theory is established, you must test it to confirm it is the actual cause. If the theory is confirmed, you move to establishing a plan of action. If not, you establish a new theory. Learn more.
Q27. You are troubleshooting a connectivity issue and see a 'Destination Host Unreachable' message. Which OSI layer is most likely the source of the problem?
- A.Layer 1 (Physical)
- B.Layer 2 (Data Link)
- C.Layer 3 (Network)✓ Correct
- D.Layer 4 (Transport)
Explanation: This error usually indicates a routing issue where the router does not have a path to the destination network, which is a Layer 3 (Network) function. Learn more.
Q28. A user can reach websites by IP address but not by name. What service should be investigated first?
- A.DNS✓ Correct
- B.DHCP only
- C.NTP
- D.PoE
Explanation: Successful IP connectivity with failed name resolution points to DNS configuration or DNS server issues. Learn more.
Q29. Which tool is best for verifying that a wall jack is connected to the expected switch port?
- A.Tone generator and probe✓ Correct
- B.Loopback plug only
- C.Crimper only
- D.Wi-Fi analyzer
Explanation: A toner and probe can trace copper cabling from a wall jack to a patch panel or switch area. Learn more.
Q30. What does a link light on a switch port usually confirm?
- A.Physical layer connectivity✓ Correct
- B.Correct DNS records
- C.Valid user permissions
- D.Successful malware scan
Explanation: A link light indicates the port has detected a physical connection and signaling with the attached device. Learn more.
Q31. Which command is commonly used to show the path packets take toward a destination?
- A.traceroute✓ Correct
- B.nslookup only
- C.arp -a only
- D.hostname
Explanation: traceroute or tracert identifies intermediate hops between a source and destination. Learn more.
Q32. Which command-line tool is commonly used to query DNS records directly?
- A.nslookup✓ Correct
- B.arp
- C.net use
- D.chmod
Explanation: nslookup queries DNS servers for name resolution records. Learn more.
Q33. Which physical issue is most likely when a copper cable test reports split pairs?
- A.Incorrect wire pairing during termination✓ Correct
- B.Wrong DNS suffix
- C.Expired certificate
- D.Low disk space
Explanation: Split pairs occur when conductors are pinned with continuity but paired incorrectly, causing signal problems. Learn more.
Q34. Which tool captures packets for protocol analysis?
- A.Wireshark✓ Correct
- B.Crimper
- C.Cable certifier only
- D.Toner probe only
Explanation: Wireshark captures and analyzes packet traffic for troubleshooting and security review. Learn more.