Pass the CompTIA CompTIA Network+ N10-009 Questions and answers with CertsForce

When an organization moves its DNS servers to new IP addresses, the NS (Name Server) records must be updated. The NS record defines which DNS servers are authoritative for a domain. Ifthese records still point to the old IP addresses, clients will continue to query the outdated servers, leading to connectivity issues.

Breakdown of Options:

A. AAAA – This record maps a domain name to an IPv6 address. Since the issue is with DNS resolution, not IP versioning, this is incorrect.

B. CNAME – A CNAME (Canonical Name) record is used for domain aliasing, not for defining authoritative name servers.

C. MX – Mail Exchange (MX) records direct email traffic to the correct mail server, which does not impact general website accessibility.

D. NS – Correct answer. NS records must be updated to reflect the new authoritative DNS servers.

The best mitigation is implementing 802.1X, which provides port-based Network Access Control (NAC). With 802.1X enabled on access switch ports, a device plugged into a wall jack cannot gain normal network access until it successfully authenticates using credentials/certificates via an authentication server (commonly RADIUS). This directly addresses the threat of unauthorized users plugging into publicly accessible conference room jacks, because the switch keeps the port in an unauthenticated state (or places it into a restricted/guest VLAN) until authentication succeeds. This aligns with Network+ security objectives that emphasize controlling access at the edge, enforcing authentication, and reducing the risk of rogue or unmanaged devices on internal networks.

MAC filtering is weaker because MAC addresses can be spoofed and managing allow-lists at scale is error-prone. Creating a trusted zone is vague and does not prevent initial port access; segmentation helps limit blast radius but doesn’t enforce authentication at the jack. Disabling unused services is a general hardening practice, but it does not stop someone from connecting physically to an active switch port and attempting access. 802.1X is purpose-built for this exact scenario.

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Understanding Link Aggregation:

Definition: Link aggregation combines multiple network connections into a single logical link to increase bandwidth and provide redundancy.

Usage in High-Bandwidth Scenarios:

Combining Links: By aggregating multiple 1Gbps connections, the facility can utilize the full 2.5Gbps bandwidth provided by the ISP.

Benefits: Enhanced throughput, load balancing, and redundancy, ensuring better utilization of available bandwidth.

Comparison with Other Options:

802.1Q Tagging: Used for VLAN tagging, which does not affect the physical bandwidth utilization.

Network Address Translation (NAT): Used for IP address translation, not related to link speed or bandwidth aggregation.

Port Duplex: Refers to the mode of communication (full or half duplex) on a port, not the aggregation of bandwidth.

Implementation:

Configure link aggregation (often referred to as LACP - Link Aggregation Control Protocol) on network devices to combine multiple physical links into one logical link.

API gateways offer programmable control and real-time communication, commonly over HTTPS, which allows administrators to update and manage devices like access points remotely and efficiently.

From Andrew Ramdayal’s guide:

“APIs enable automation and real-time interaction with network devices via secure interfaces, often using HTTPS for encrypted communication and control.”

When dealing with troubleshooting and change management, the plan of action outlines the steps, risks, and mitigation strategies. A change advisory board (CAB) uses this documented plan to decide whether to approve the change.

A. Identify the problem is the first step in troubleshooting, not decision-making for CAB.

B. Develop a theory is diagnostic work, not planning.

C. Test the theory confirms causes but doesn’t provide actionable planning information.

References (CompTIA Network+ N10-009):

Domain: Network Operations — Change management, troubleshooting methodology, CAB processes.

Port 587 is the standard default port for sending email (SMTP) with TLS encryption, which is used to secure email transmissions between mail servers or between clients and mail servers. Allowing traffic over port 587 enables secure email sending while maintaining standard protocol usage. (Reference: CompTIA Network+ Study Guide, Chapter on Ports and Protocols)

On Core-SW01, the ports are configured with LACP (mode active) for link aggregation. On Core-SW02, the ports are configured as independent trunks, not as part of an LACP group. Because of this mismatch, LACP cannot form the bundle, and the aggregated ports on SW01 will go into a suspended state.

A. CRC errors suggest cabling or signal integrity issues, not config mismatch.

B. Error disabled occurs when a violation (like BPDU guard or port security) disables the port, not LACP mismatch.

C. Administratively down indicates a shutdown command, not the case here.

References (CompTIA Network+ N10-009):

Domain: Network Troubleshooting — Port-channel/LACP configuration issues, interface states.

A UPS (Uninterruptible Power Supply) and PDU (Power Distribution Unit) are installed to provide reliable, properly distributed electrical power to network equipment—especially in wiring closets such as an IDF and in main equipment rooms. In Network+ (N10-009) infrastructure objectives, a UPS protects against power loss and instability by supplying battery-backed power during outages and often providing conditioning to reduce the impact of sags, spikes, and brief interruptions. A PDU then distributes that power to multiple devices in a rack (switches, routers, firewalls, AP controllers), often offering organized outlets and, in managed models, monitoring/control features.

Option A is the best match because it reflects the practical purpose: ensuring network devices receive appropriate and continuous power in distribution frames/closets. Option B is partially related, but “managing power consumption in the MDF” is too narrow and not as accurate as the broader function of providing backup and distribution power. Option C describes a network switch, not power equipment. Option D refers to HVAC/environmental controls, not UPS/PDU functionality. Hence, A is correct.

If the user cannot communicate with 192.168.10.1, they might be on a different subnet. Changing the subnet mask to 255.255.255.0 ensures the user and the file server are in the same subnet.

Breakdown of Options:

A. Changing the IPv4 address to 192.168.10.1 – This would conflict with the server ' s IP.

B. Changing the subnet mask to 255.255.255.0 – ✅ Correct answer. Ensures both the user and the server are on the same subnet.

C. Changing the DNS servers – DNS does not affect local network connectivity.

D. Changing the physical address – The MAC address does not impact subnet communication.

Definition of Fiber Connector Types:

LC (Lucent Connector): A small form-factor fiber optic connector with a push-pull latching mechanism, commonly used for high-density applications.

SC (Subscriber Connector or Standard Connector): A larger form-factor connector with a push-pull latching mechanism, often used in datacom and telecom applications.

ST (Straight Tip): A bayonet-style connector, typically used in multimode fiber optic networks.

MPO (Multi-fiber Push On): A connector designed to support multiple fibers (typically 12 or 24 fibers), used in high-density cabling environments.

Common Usage:

LC Connectors: Due to their small size, LC connectors are widely used in network interface cards (NICs) and high-density environments such as data centers. They allow for more connections in a smaller space compared to SC and ST connectors.

SC and ST Connectors: These are larger and more commonly used in patch panels and older fiber installations but are less suitable for high-density applications.

MPO Connectors: Primarily used for trunk cables in data centers and high-density applications but not typically on individual network interface cards.

Selection Criteria:

The small form-factor and high-density capabilities of LC connectors make them the preferred choice for network interface cards, where space and connection density are critical considerations.

To determine where slowness is occurring—especially if an upstream router is suspected—the best tools are ping and tracert/traceroute. Network+ (N10-009) troubleshooting objectives emphasize using these to test connectivity, latency, and the path packets take through the network. Ping measures reachability and round-trip time; rising latency or packet loss can indicate congestion or a failing link/device. Tracert identifies each hop along the route and reports per-hop response times, helping pinpoint whether delays begin at a specific hop (for example, the default gateway, the upstream router, or a provider edge). This allows the engineer to localize the problem area and decide whether the issue is internal, at the upstream router, or beyond.

nslookup and dig are DNS tools; they diagnose name resolution, not general network slowness location. Nmap focuses on scanning ports/hosts, and a “speed tester” measures throughput but does not locate the failing hop. tcpdump and protocol analyzer can reveal retransmissions, windowing, or application behavior, but they are not the fastest first-choice tools for locating an upstream routing/performance bottleneck across hops. Hence, tracert and ping are the correct pair.

When traffic moves laterally between VMs within the same network or subnet, it is known as east-west traffic. This contrasts with north-south traffic, which refers to communication between internal and external networks.

Breakdown of Options:

A. East-west – Correct answer. This refers to traffic between internal servers or VMs, which is a common security concern.

B. Point-to-point – Point-to-point describes a direct connection between two devices, but does not specifically define lateral movement.

C. Horizontal-scaling – This refers to adding more instances or nodes in cloud computing, unrelated to traffic flow.

D. Hub-and-spoke – This network topology describes a centralized design, not lateral traffic.

Full duplex mode allows devices to send and receive data simultaneously, improving network performance and reducing congestion, which is critical for VoIP and video conferencing.

Breakdown of Options:

A. A VLAN with 100Mbps speed limits – VLANs segment traffic but limiting speeds to 100Mbps would worsen video performance.

B. An IP helper to direct VoIP traffic – IP helper is used for DHCP relay, not for VoIP optimization.

C. A smaller subnet mask – A smaller subnet reduces IP address availability but does not improve network performance.

D. Full duplex on all user ports – Correct answer. Full duplex eliminates collisions, allowing better VoIP and video performance.

The correct solution is to configure the connecting ports as trunk ports. When connecting switches, the uplink ports must be configured to carry traffic for multiple VLANs (trunking), not just a single access VLAN. Without trunking, VLAN tags may be dropped, and traffic from hosts will not reach the rest of the network or internet.

B. STP cables is a misnomer — STP refers to Spanning Tree Protocol or Shielded Twisted Pair cables, neither of which solves this logical configuration issue.

C. PoE budget is irrelevant because switches and hosts in this context don’t require PoE.

D. Link aggregation (LACP, EtherChannel) is for increasing bandwidth/redundancy across multiple links, not required with a single cable.

By enabling trunking on the uplink ports, the switches can pass VLAN-tagged traffic, ensuring hosts connected to the new switch have access to the same resources as those on the existing switch.

References (CompTIA Network+ N10-009):

Domain: Network Troubleshooting — VLAN trunking, inter-switch connectivity.

The CompTIA Troubleshooting Methodology states that after testing the theory, the next step is to establish a plan of action to resolve the issue.

Troubleshooting Steps:

Identify the problem.

Establish a theory of probable cause.

Test the theory to determine the cause.

Establish a plan of action and implement the solution. ✅ (Correct step)

Verify full system functionality.

Document findings, actions, and outcomes.

Breakdown of Options:

A. Verify full system functionality – Happens after implementing the solution.

B. Document the findings and outcomes – Final step, happens after resolving the issue.

C. Establish a plan of action – ✅ Correct answer. Comes immediately after confirming the cause.

D. Identify the problem – First step, already completed.