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This page has 15 Troubleshooting Scenario Questions scenario questions for the N10-009 exam, each with detailed explanations and wrong-answer analysis.

How should I approach N10-009 scenario questions?

Read the full scenario before looking at the answer options. Identify the constraint or requirement in the scenario, then eliminate options that are generally true but wrong for this specific case. Scenario questions reward careful reading over pattern matching.

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Troubleshooting Scenario Questions

Practise CompTIA Network+ N10-009 practice questions — original exam-style scenarios covering every exam domain, with detailed explanations, wrong-answer analysis, and common exam traps.

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scenario questions

N10-009

exam code

CompTIA

vendor

Scenario guide

How to approach troubleshooting scenario questions

These questions describe a network symptom and ask you to identify the root cause or the correct fix. They appear across all certification exams and reward systematic thinking over memorisation. The best candidates follow a consistent troubleshooting framework even under time pressure.

Quick answer

Troubleshooting Scenario Questions questions test whether you can apply the concept in context, not just recognise a definition.

How the topic appears in realistic exam-style scenarios.

Which detail in the question changes the correct answer.

How to eliminate plausible but wrong options.

How to connect the question back to the wider exam objective.

Practice scenarios

Question 1hardmultiple choice

Read the full VPN explanation →

A network engineer has successfully established an IPsec site-to-site VPN tunnel between a branch office (10.0.1.0/24) and the main office (192.168.1.0/24). The tunnel status shows as active, and both sides can ping each other's tunnel interface IP addresses. However, users at the branch office cannot ping the main office server at 192.168.1.10, and the main office cannot ping the branch office server at 10.0.1.10. The firewall rules on both sides permit IPsec traffic and all internal traffic. What should the engineer check NEXT?

A
Verify routing entries on both routers to ensure the remote internal subnets are reachable via the tunnel.
Both routers need to have routes pointing to the remote internal subnets (e.g., 192.168.1.0/24 and 10.0.1.0/24) with the tunnel interface as the next hop. Without these routes, traffic from internal hosts will not be directed into the tunnel.
B
Check the IPsec security associations for encryption algorithm mismatch.
Why wrong: If the tunnel is active and both sides can ping tunnel IPs, the IPsec parameters are correctly negotiated. An algorithm mismatch would prevent the tunnel from establishing.
C
Disable the firewall on the internal interfaces temporarily.
Why wrong: The firewall rules already permit traffic. Disabling firewalls is not a best practice and would not resolve a routing issue.
D
Regenerate the pre-shared key on both sides.
Why wrong: Regenerating the PSK is unnecessary because the tunnel is already established. The PSK is only used during initial authentication.

Full breakdown with real-world context →

Question 2hardmultiple choice

Read the full DNS explanation →

A user reports intermittent inability to access websites. When the issue occurs, the user can ping external IP addresses (e.g., 8.8.8.8) but cannot ping domain names like google.com. The user's IP configuration shows a DNS server address of 8.8.8.8. What is the most likely cause?

A
The DNS server is reachable but not responding due to high load.
Correct. If the DNS server is overloaded, it may drop queries intermittently. The user can still ping the server (ICMP is different from DNS), but DNS queries time out.
B
The default gateway is down.
Why wrong: If the default gateway were down, the user would not be able to ping any external IP addresses. The fact that pinging 8.8.8.8 works rules this out.
C
The corporate firewall is blocking UDP port 53.
Why wrong: A firewall block on UDP port 53 would cause DNS failures consistently, not intermittently. The user would never be able to resolve domain names.
D
The user's machine has a corrupted DNS cache.
Why wrong: A corrupted DNS cache typically causes failures for specific cached entries, but the issue is described as intermittent and affects all domain names. Flushing the cache might resolve it, but the intermittent nature points more to server load.

Full breakdown with real-world context →

Question 3mediummultiple choice

Open the full VLAN trunking answer →

A network administrator is troubleshooting communication between two switches connected via a trunk port. The trunk link is up/up, but devices in VLAN 20 cannot communicate across the trunk. The administrator has verified that both switches have VLAN 20 created and that the access ports are configured correctly. Which command should the administrator run on each switch to verify the trunk's allowed VLAN list?

A
show vlan brief
Why wrong: This command shows VLAN information but does not display trunk-specific allowed VLAN lists for each trunk interface.
B
show interfaces trunk
Correct. This command displays detailed trunk status, including the allowed VLAN list, native VLAN, and trunking mode, helping to verify if VLAN 20 is allowed.
C
show running-config interface
Why wrong: While this shows the configuration, it may not show the default allowed VLAN list if not explicitly configured; 'show interfaces trunk' is more direct.
D
show mac address-table
Why wrong: This command shows MAC address table entries, not trunk configuration.

Full breakdown with real-world context →

Question 4mediummultiple choice

Full question →

A network administrator is troubleshooting an intermittent link between two switches connected by single-mode fiber. The interface log shows "Link up / Link down" events multiple times per hour. Which of the following is the most likely cause?

A
Incorrect VLAN configuration on the switch ports
Why wrong: VLAN mismatches typically result in connectivity issues or traffic errors, but they do not usually cause the physical link to flap (repeatedly lose carrier).
B
Crossed fiber pairs
Why wrong: Crossed pairs (transmit/receive swapped) would prevent the link from ever establishing, not cause intermittent flapping.
C
Dirty fiber connectors
Dirty connectors can cause intermittent signal loss as the light is partially blocked. This is a common cause of flapping fiber links. Cleaning the connectors often resolves the issue.
D
Duplex mismatch between the switches
Why wrong: Duplex mismatch usually results in high error rates, collisions, and poor performance, but the link state remains up. It does not typically cause link flapping.

Full breakdown with real-world context →

Question 5hardmultiple choice

Full question →

A network technician is troubleshooting an intermittent connectivity issue between two switches connected via fiber optic cable. The link status shows up/down flapping. The technician checks the optical power levels and finds they are within acceptable range. Which of the following is the most likely cause?

A
Dirty fiber connectors
Contamination on fiber end faces can cause intermittent signal degradation and link flapping.
B
Electromagnetic interference
Why wrong: Fiber optic cables are immune to EMI.
C
Incorrect VLAN configuration
Why wrong: VLAN misconfiguration would cause traffic issues but not physical link flapping.
D
Duplex mismatch
Why wrong: Duplex mismatch is common on copper links, not fiber, and typically causes constant errors, not intermittent flapping.

Full breakdown with real-world context →

Question 6mediummultiple choice

Read the full wireless explanation →

A network technician is installing a new wireless access point in a warehouse. The AP requires PoE+ (802.3at) for full operation. The technician connects the AP using a Cat5e cable run of 200 feet to a switch that only supports 802.3af (PoE). The AP powers on but has intermittent connectivity issues. What is the most likely cause?

A
The cable length exceeds the maximum for PoE
Why wrong: The maximum Ethernet cable length for PoE is 100m (328 ft). 200 ft is within this limit, so cable length is not the issue.
B
The switch does not support the required PoE standard
The AP requires 802.3at (PoE+ providing up to 30W), but the switch only provides 802.3af (up to 15.4W). Insufficient power can cause erratic behavior and connectivity drops.
C
The AP is experiencing interference from metal racks
Why wrong: While metal racks can cause wireless interference, the primary symptom described is intermittent connectivity after cabling, pointing to a power issue.
D
The AP is configured with the wrong SSID
Why wrong: An incorrect SSID would prevent clients from seeing the network, not cause intermittent connectivity after power-on.

Full breakdown with real-world context →

Question 7mediummultiple choice

Full question →

A technician is troubleshooting a connectivity issue. The technician can successfully ping the IP address of a web server (10.10.10.10) from a client, but the client cannot access the web page. Firewall rules allow HTTP traffic. At which OSI layer is the issue most likely occurring?

A
Application layer (Layer 7)
Correct. The web service (HTTP) is an Application layer protocol. If the service is not running or misconfigured, the client cannot access the web page despite lower-layer connectivity.
B
Session layer (Layer 5)
Why wrong: The Session layer manages sessions, but HTTP is an Application layer protocol. Session issues are less likely given successful lower-layer communication.
C
Transport layer (Layer 4)
Why wrong: Since the firewall allows HTTP traffic, a Transport layer block is unlikely. If it were a port issue, ping would still work, but the symptom would be consistent with a firewall block. However, the most likely cause is the Application layer.
D
Network layer (Layer 3)
Why wrong: Successful ping confirms that the Network layer (IP addressing and routing) is functioning correctly. The problem is at a higher layer.

Full breakdown with real-world context →

Question 8mediummultiple choice

Full question →

A network technician is troubleshooting a user's inability to connect to the network. The switch port is configured with port security with the default maximum of one MAC address. The user connects a computer and a VoIP phone to the port using the phone's built-in switch. Which of the following will MOST likely occur?

A
The port will go into errdisable state
The second MAC address triggers a port security violation, causing the port to be disabled.
B
The phone will work but the computer will not
Why wrong: Port security blocks all traffic from the second MAC, but the switch will typically disable the entire port, not just the computer's traffic.
C
Both devices will work because the phone uses a different MAC
Why wrong: The phone and computer have two unique MAC addresses, exceeding the limit, so a violation occurs.
D
The switch will allow only the first learned MAC and block the second
Why wrong: Port security can operate in restrict or shutdown mode; the default shutdown mode disables the port entirely.

Full breakdown with real-world context →

Question 9mediummultiple choice

Read the full wireless explanation →

A technician is troubleshooting intermittent wireless connectivity in a conference room. A site survey shows strong signal strength but many nearby access points are using channels that overlap with the channel used by the conference room AP. Which of the following is the most likely cause of the issue?

A
Multipath interference from reflective surfaces.
Why wrong: Multipath interference can cause signal degradation, but the given scenario points to overlapping channels as the cause.
B
Co-channel interference from access points on the same channel.
Why wrong: Co-channel interference occurs when APs use the exact same channel, not overlapping ones.
C
Adjacent channel interference from access points on overlapping channels.
Overlapping channels cause adjacent channel interference, reducing throughput and causing intermittent connectivity.
D
Signal attenuation due to distance from the AP.
Why wrong: The site survey shows strong signal strength, so attenuation is not the issue.

Full breakdown with real-world context →

Question 10mediummultiple choice

Read the full NAT/PAT explanation →

A network technician is troubleshooting a workstation that is experiencing intermittent connectivity and slow file transfers. The technician has confirmed that the patch cable passes a cable tester, the switch port is not error-disabled, and the workstation's NIC is configured for autonegotiation. The switch port is also set to autonegotiate. Which of the following should the technician check next?

A
The route table on the default gateway
Why wrong: Routing issues typically affect connectivity between subnets, not local intermittent performance. The workstation can still communicate locally, so routing is likely not the cause.
B
The duplex and speed settings on both ends
Autonegotiation can fail, resulting in a duplex mismatch where one side runs at half-duplex and the other at full-duplex. This causes collisions and retransmissions, leading to intermittent connectivity and slow transfers.
C
The DNS server configuration
Why wrong: DNS issues would cause name resolution failures, not intermittent connectivity or slow file transfers. File transfers use IP addresses after initial resolution.
D
The MAC address filtering on the switch
Why wrong: MAC filtering would either block traffic completely or allow it; it does not cause intermittent performance issues. The workstation is connected, so filtering is not the problem.

Full breakdown with real-world context →

Question 11mediummultiple choice

Open the full VLAN trunking answer →

A user's computer is unable to obtain a DHCP lease after connecting to a new switch port. The user's computer displays an IP address in the 169.254.x.x range. Other users on the same VLAN can obtain IP addresses successfully. The switch port is configured for 802.1X authentication. What is the most likely cause?

A
The DHCP server has exhausted its address pool.
Why wrong: If the DHCP server were out of addresses, other users on the same VLAN would also fail to obtain leases. This is inconsistent with the scenario.
B
The switch port is in a blocked state due to a spanning tree loop.
Why wrong: A spanning tree loop would affect all devices on that port, not just DHCP, and would likely cause intermittent connectivity. Also, the port should transition to forwarding after convergence.
C
The user's computer has not authenticated via 802.1X and is placed in a restricted VLAN.
With 802.1X, unauthenticated devices are often placed in a restricted VLAN that may not include the DHCP server or have limited access. This explains why the computer gets an APIPA address while other devices on the same physical port (if authenticated) work normally.
D
The network cable is faulty.
Why wrong: If the cable were faulty, the link would likely be down or have excessive errors. The computer obtained a link and attempted DHCP, so a cable fault is improbable.

Full breakdown with real-world context →

Question 12mediumdrag order

Full question →

Drag and drop the steps to troubleshoot a network connectivity issue using the OSI model into the correct order (top-down approach).

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 13mediummultiple choice

Read the full DNS explanation →

Users in a small office can access external websites normally, but they cannot reach the internal company wiki server at 192.168.10.25. A technician can successfully ping the server's IP address from a user's workstation. The DNS resolution for the wiki's hostname (wiki.company.local) returns the correct IP. The company's firewall permits HTTP traffic to the server. What is the most likely cause of the issue?

A
The web server service is not running or is listening on a different port
Correct. If the service is not available, the browser cannot establish a TCP connection to the web server, even though network connectivity exists.
B
The default gateway on the server is misconfigured
Why wrong: If the server's gateway were misconfigured, ping replies would likely fail or be asymmetric. Since ping works, the gateway is probably fine.
C
The user's workstation has a duplicate IP address
Why wrong: A duplicate IP would cause intermittent connectivity issues and likely affect ping as well, but the symptom is isolated to web access.
D
The DNS cache on the workstation is poisoned
Why wrong: The technician confirmed that DNS resolves correctly to 192.168.10.25, so DNS is not the issue.

Full breakdown with real-world context →

Question 14easymultiple choice

Full question →

A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?

A
Transport layer
Why wrong: The Transport layer is responsible for end-to-end communication and segmentation, not physical cabling.
B
Data Link layer
Why wrong: The Data Link layer handles framing and MAC addressing, but not the physical medium itself.
C
Physical layer
The Physical layer defines the electrical, mechanical, and procedural interface to the transmission medium, making it the correct layer for cabling issues.
D
Network layer
Why wrong: The Network layer handles logical addressing and routing, not physical connections.

Full breakdown with real-world context →

Question 15hardmultiple choice

Full question →

A network engineer is troubleshooting connectivity issues between two data center switches that are configured to support jumbo frames with an MTU of 9000. The link is a 10 Gigabit Ethernet fiber connection. Large file transfers fail, but small transfers succeed. What is the most likely cause?

A
A
Why wrong: 10 Gigabit Ethernet is widely supported and not the cause of this specific issue.
B
B
Why wrong: While a faulty fiber cable could cause general failures, the pattern of small transfers working and large transfers failing points to an MTU issue.
C
C
An intermediate device with a standard MTU will drop large frames, causing jumbo frame traffic to fail.
D
D
Why wrong: TCP window size affects throughput but not the ability to transfer large files at all; small transfers would also fail if window size were severely misconfigured.

Full breakdown with real-world context →

These N10-009 practice questions are part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style N10-009 questions with detailed explanations, topic-based practice, mock exams, readiness tracking, and study analytics.

Troubleshooting Scenario Questions

How to approach troubleshooting scenario questions

Quick answer

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Practice scenarios

A user reports intermittent inability to access websites. When the issue occurs, the user can ping external IP addresses (e.g., 8.8.8.8) but cannot ping domain names like google.com. The user's IP configuration shows a DNS server address of 8.8.8.8. What is the most likely cause?

A network administrator is troubleshooting an intermittent link between two switches connected by single-mode fiber. The interface log shows "Link up / Link down" events multiple times per hour. Which of the following is the most likely cause?

A technician is troubleshooting a connectivity issue. The technician can successfully ping the IP address of a web server (10.10.10.10) from a client, but the client cannot access the web page. Firewall rules allow HTTP traffic. At which OSI layer is the issue most likely occurring?

Drag and drop the steps to troubleshoot a network connectivity issue using the OSI model into the correct order (top-down approach).

A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?

A network engineer is troubleshooting connectivity issues between two data center switches that are configured to support jumbo frames with an MTU of 9000. The link is a 10 Gigabit Ethernet fiber connection. Large file transfers fail, but small transfers succeed. What is the most likely cause?