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

When two devices on different subnets are unable to communicate, but can communicate with other devices on their own subnet, the issue is most often related to routing. Devices on different subnets require a default gateway to route traffic between networks.

If the default gateway is incorrectly configured, the device won’t know how to reach other subnets.

Faulty cables (Option B) or duplex mismatches (Option C) would likely cause connectivity issues even within the local subnet, which is not the case here.

VLAN mismatches (Option D) are typically issues with switch port configurations and would likely cause total loss of connectivity, including within the same subnet.

✅ So, the most probable and logical cause is an incorrect default gateway.

802.1X is a port-based Network Access Control (NAC) method that enforces authentication before allowing access to the network. It uses a RADIUS server for identity verification and policy enforcement, ensuring only authorized users/devices gain access.

A. Standard ACL filters traffic by IP, not identity.

B. MAC filtering controls devices by hardware address but can be spoofed.

D. SSO (Single Sign-On) provides user convenience across services, not network-level access control.

References (CompTIA Network+ N10-009):

Domain: Network Security — NAC, 802.1X authentication, identity-based access.

The best answer is B. 255.255.252.0, which is a /22 mask. A Class B network starts with a default mask of 255.255.0.0 or /16. The question says the administrator wants four equal subnets, which means borrowing 2 bits from the host portion, since 2 borrowed bits gives 2² = 4 subnets. That moves the mask from /16 to /18 if subnetting is based only on splitting the Class B into four equal parts.

However, the answer choices point toward the host requirement as the deciding factor. Each subnet needs to support about 1,000 hosts. A /22 leaves 10 host bits, which gives 2¹⁰ = 1024 total addresses, or 1022 usable hosts after subtracting the network and broadcast addresses. That fits the requirement. Among the options provided, 255.255.252.0 is the only mask that supports around 1,000 hosts per subnet.

The smaller masks, /24 and /25, do not allow enough hosts. The default Class B mask, /16, does not subnet the network at all. Based on the available choices and the host-capacity requirement, 255.255.252.0 is the correct exam answer.

The correct solution is NTP (Network Time Protocol). Accurate timestamps across servers, firewalls, and network devices are critical for correlating logs during incident response. NTP synchronizes device clocks to a trusted time source, ensuring consistency across the network.

A. Syslog centralizes logs but does not synchronize time.

B. SMTP is email transfer, unrelated to time.

D. SNMP monitors devices but does not correct time discrepancies.

By implementing NTP, analysts can ensure that logs from different devices are time-aligned, which is essential for reconstructing attack timelines and detecting anomalies.

References (CompTIA Network+ N10-009):

Domain: Network Operations — Time synchronization, NTP, log correlation.

The correct answer is /25, which is the appropriate subnet mask for dividing an existing Class C network into two equal subnets. According to the CompTIA Network+ N10-009 objectives, subnetting is a core networking concept used to improve network segmentation, performance, and security.

A Class C network uses a default subnet mask of /24 (255.255.255.0), which provides 256 total addresses (254 usable). To split this network into two sections, the administrator must borrow one host bit from the last octet. Borrowing one bit results in a /25 subnet mask (255.255.255.128). This creates two subnets, each with 128 total addresses (126 usable)—an ideal solution for separating two departments such as finance and marketing.

A /24 would not create any segmentation, as it represents the original single network. A /26 would create four subnets, and a /27 would create eight subnets, both of which exceed the requirement of only two sections and unnecessarily reduce the number of available host addresses per subnet.

The Network+ objectives emphasize selecting subnet masks based on organizational requirements, balancing the number of subnets with sufficient host capacity. In this scenario, /25 is the most efficient and correct choice.

SSH (Secure Shell) is a protocol used to securely connect to a remote server/system over a network. It operates on port 22 and provides encrypted communication, unlike Telnet which operates on port 23 and is not secure. TLS is used for securing HTTP connections (HTTPS) and operates on ports like 443, while RDP (Remote Desktop Protocol) is used for remote desktop connections and operates on port 3389.

A transceiver is the correct answer because it is the Layer 1 (Physical Layer) component that physically terminates and converts fiber-optic signals on an SFP-capable switch. In CompTIA Network+ N10-009 objectives, transceivers—such as SFP, SFP+, QSFP, and QSFP+ modules—are explicitly identified as physical interface components that handle signal transmission and reception. These modules convert electrical signals from the switch into optical signals for fiber cabling (and vice versa), enabling communication over different media types and distances.

A modem is also a Layer 1 device, but its purpose is to modulate and demodulate signals for WAN technologies such as DSL or cable—it does not terminate fiber connections on switches. An Ethernet NIC provides network access for end devices like computers and servers and typically terminates copper Ethernet, not modular fiber interfaces on switches. A repeater regenerates and amplifies signals to extend cable distances but does not provide fiber termination or media conversion at a switch port.

According to Network+ standards, SFP transceivers are essential for flexible network design, allowing administrators to select appropriate fiber types (single-mode or multi-mode), wavelengths, and distances while remaining compliant with physical layer requirements.

Spanning Tree Protocol (STP) uses bridge priority values to determine the root bridge in a switched network topology. Correctly configuring bridge priority helps in maintaining a loop-free and efficient network. The document explains:

“Spanning Tree Protocol (STP) uses bridge priority values to determine which switch will be the root bridge, ensuring loop prevention and efficient path selection within the network.”

Secure Shell (SSH) is a protocol used to securely access remote devices over an unsecured network. It provides encrypted command-line access and is a lightweight and secure method of remote administration.

A. Site-to-site VPN connects entire networks, not just a single host.

B. Telnet is not secure; it transmits data (including credentials) in plaintext.

C. Console access is direct via serial cable, not remote.

???? Reference:

CompTIA Network+ N10-009 Official Objectives: 2.6 – Configure and troubleshoot remote access.

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.

Adding more access points can improve coverage, but it also increases the risk of co-channel interference if APs are configured on the same or overlapping channels. Channel overlap causes contention and interference, leading to retries, unstable performance, and symptoms that feel like frequent disconnect/reconnect events—especially in dense deployments. Network+ (N10-009) wireless troubleshooting objectives highlight proper channel planning (non-overlapping channels, appropriate channel width) as critical when increasing AP density. If adjacent APs are competing on the same channel (or overlapping channels in 2.4 GHz), clients may experience poor signal-to-noise ratios and repeated reassociations as they struggle to maintain a stable link.

Roaming misconfiguration can cause sticky clients or poor handoffs, but the classic problem introduced immediately after “adding more APs” is interference from bad channel design. Throughput capacity is about available bandwidth and airtime efficiency; it can make things slow, but it doesn’t inherently cause repeated disconnect/reconnect loops like interference does. Packet loss is a symptom that may occur due to interference, but the root cause in the options that best fits the scenario is channel overlap.

•A. Isolate smart devices to their own network segment: Network segmentation using VLANs or separate SSIDs ensures that smart devices (like speakers) are not on the same network as guests, preventing unauthorized control.

•E. Change the default credentials: Many IoT devices (e.g., smart speakers) come with default usernames and passwords. If these are not changed, unauthorized users can easily take control.

•Why not the other options?

•B. Configure IPS: IPS (Intrusion Prevention System) detects threats but cannot block specific guest actions on an IoT device.

•C. Install a new AP: A new access point does not solve the unauthorized control issue.

•D. Set up a syslog server: Helps with logging, but does not prevent unauthorized access.

•F. Configure GRE: Generic Routing Encapsulation (GRE) is used for VPN tunneling, which is irrelevant in this case.

TCP port 443 is reserved for HTTPS (Hypertext Transfer Protocol Secure), which uses TLS encryption to secure web traffic. It is the standard port for encrypted web communications.

A. Telnet uses TCP port 23.

B. SMTP commonly uses TCP ports 25, 465, or 587.

D. SNMP typically uses UDP ports 161 (queries) and 162 (traps).

References (CompTIA Network+ N10-009):

Domain: Network Standards, Protocols, and Implementations — Common ports and services.

The correct answer is A. TACACS+. This protocol is commonly used for authentication, authorization, and accounting (AAA) when administrators need to access network infrastructure devices such as routers, switches, and firewalls. The key part of the question is not just authentication, but also logging capabilities. TACACS+ supports accounting functions, which means it can record administrative actions and login events. That makes it especially useful when organizations want traceability for device access and configuration changes.

The other options do not fit as well. SAML is primarily used for federated identity and web-based authentication between identity providers and service providers. SSO is a general authentication convenience feature that allows one login to access multiple systems, but it does not itself provide detailed device-level accounting. MFA strengthens authentication by requiring multiple factors, but it is not the protocol best known for centralized access control and activity logging on network devices.

For Network+ exam purposes, TACACS+ is strongly associated with administrative access to network equipment and with maintaining an audit trail of who accessed devices and what actions were performed. Because the question asks for both simple authentication and logging, TACACS+ is the best match.