CompTIA Network+ — All Questions

Which layer of the OSI model is responsible for logical addressing and determining the best path for packets across an internetwork?

• a.Layer 1 (Physical)
• b.Layer 4 (Transport)
• c.Layer 3 (Network)✓
• d.Layer 2 (Data Link)

Layer 3, the Network layer, handles logical addressing such as IP and makes routing decisions to move packets between networks. The Data Link layer uses physical MAC addresses for local delivery, while the Transport layer manages end-to-end segmentation. Routers operate primarily at Layer 3.

A network administrator needs to identify the protocol data unit (PDU) used at the Transport layer of the OSI model. Which term applies?

• a.Packet
• b.Bit
• c.Frame
• d.Segment✓

At the Transport layer the PDU is called a segment (or datagram for UDP). Packets exist at the Network layer, frames at the Data Link layer, and bits at the Physical layer. Knowing PDU names per layer helps when interpreting protocol behavior.

Which protocol and port number are used by HTTPS for secure web traffic by default?

• a.TCP 443✓
• b.UDP 53
• c.TCP 80
• d.TCP 22

HTTPS uses TCP port 443 and secures web traffic with TLS. Port 80 is plain HTTP, port 53 is DNS, and port 22 is SSH. Memorizing well-known ports is essential for firewall and troubleshooting work.

What is the default port used by the Domain Name System (DNS) for standard name resolution queries?

• a.TCP 110
• b.UDP 53✓
• c.TCP 25
• d.UDP 67

DNS uses UDP port 53 for most standard queries because they are small and benefit from low overhead. TCP 53 is used for zone transfers and larger responses. Ports 25, 110, and 67 belong to SMTP, POP3, and DHCP respectively.

An engineer must choose an address class for a private network that supports up to 500 hosts on a single subnet. Which private range is most appropriate to draw from?

• a.10.0.0.0/8✓
• b.224.0.0.0/4
• c.127.0.0.0/8
• d.169.254.0.0/16

The 10.0.0.0/8 range is an RFC 1918 private block that easily provides subnets large enough for 500 hosts. 169.254.0.0/16 is APIPA link-local, 224.0.0.0/4 is multicast, and 127.0.0.0/8 is loopback. Private ranges avoid public IP consumption.

How many usable host addresses are available in a subnet with a /29 prefix?

• a.4
• b.8
• c.2
• d.6✓

A /29 leaves 3 host bits, giving 2^3 = 8 total addresses, minus the network and broadcast addresses, for 6 usable hosts. Subnetting math requires subtracting two reserved addresses from the total. /29 subnets are common for small point-to-point or device segments.

Which IPv6 address type begins with the prefix FE80::/10 and is used only for communication on the local link?

• a.Link-local✓
• b.Global unicast
• c.Anycast
• d.Multicast

Link-local IPv6 addresses use the FE80::/10 prefix and are auto-configured on every interface for local-link communication. Global unicast addresses are routable on the internet, while multicast uses FF00::/8. Link-local addresses are never routed beyond the local segment.

A star topology relies on which central device to interconnect all end nodes?

• a.A central switch or hub✓
• b.A ring of daisy-chained cables
• c.A repeater between each pair of nodes
• d.A shared coaxial bus

In a star topology every node connects to a central switch or hub, which forwards traffic between them. A failure of one cable affects only that node, improving fault isolation. Bus and ring topologies use shared media that create single points of failure.

Which cabling standard defines the maximum supported distance of 100 meters for a twisted-pair Ethernet run?

• a.1000BASE-LX
• b.10GBASE-ER
• c.1000BASE-T✓
• d.100BASE-FX

1000BASE-T runs over twisted-pair copper and is limited to 100 meters per segment. The other options are fiber standards that support much longer distances. The 100-meter copper limit includes patch cords and horizontal cabling.

What is the primary purpose of a VLAN in a switched network?

• a.To convert Layer 2 frames into Layer 3 packets
• b.To provide power to connected devices
• c.To increase the speed of individual switch ports
• d.To logically segment a physical switch into separate broadcast domains✓

A VLAN logically segments a switch so that ports belong to separate broadcast domains without needing additional physical switches. This improves security and reduces broadcast traffic. Routing between VLANs still requires a Layer 3 device.

Which protocol resolves an IPv4 address to a MAC address on a local Ethernet segment?

• a.ARP✓
• b.ICMP
• c.DNS
• d.NTP

ARP (Address Resolution Protocol) maps a known IPv4 address to the MAC address needed for Layer 2 delivery. DNS resolves names to IPs, ICMP handles diagnostics, and NTP synchronizes time. ARP operates only within a local broadcast domain.

A company wants clients to obtain IP configuration automatically. Which protocol assigns addresses, subnet masks, gateways, and DNS servers dynamically?

• a.LDAP
• b.DHCP✓
• c.SNMP
• d.DNS

DHCP dynamically leases IP addresses along with subnet mask, default gateway, and DNS server information to clients. This eliminates manual configuration and reduces addressing errors. DHCP uses UDP ports 67 and 68 for server and client communication.

In the TCP three-way handshake, which sequence of flags correctly establishes a connection?

• a.ACK, SYN-ACK, SYN
• b.SYN, SYN-ACK, ACK✓
• c.PSH, URG, ACK
• d.FIN, ACK, RST

The TCP three-way handshake proceeds as SYN, then SYN-ACK, then ACK to establish a reliable session. FIN and RST relate to closing or resetting connections. Understanding the handshake helps diagnose connection setup failures.

Which cloud service model provides virtual machines, storage, and networking that customers manage themselves?

• a.PaaS
• b.IaaS✓
• c.DaaS
• d.SaaS

Infrastructure as a Service (IaaS) delivers fundamental compute, storage, and network resources that the customer configures and manages. SaaS delivers finished applications, and PaaS provides a development platform. IaaS offers the most customer control among cloud models.

What distinguishes UDP from TCP at the Transport layer?

• a.UDP guarantees ordered delivery through sequencing
• b.UDP always encrypts application data
• c.UDP performs a three-way handshake before sending data
• d.UDP is connectionless and does not guarantee delivery✓

UDP is connectionless, has low overhead, and does not guarantee delivery, ordering, or retransmission. This makes it ideal for latency-sensitive traffic such as VoIP and streaming. TCP, by contrast, is connection-oriented and reliable.

A /24 network needs to be divided into four equal subnets. Which new prefix length should be used?

• a./27
• b./28
• c./26✓
• d./25

Borrowing two host bits from a /24 creates four subnets, resulting in a /26 prefix. Each /26 subnet provides 62 usable hosts. The formula 2^n subnets requires n borrowed bits, so 2^2 equals four subnets.

Which network device forwards frames based on MAC address tables and operates primarily at Layer 2?

• a.Firewall
• b.Router
• c.Switch✓
• d.Load balancer

A switch builds a MAC address table and forwards frames only to the port associated with the destination MAC, operating at Layer 2. Routers work at Layer 3 using IP addresses. Switching reduces collisions by creating dedicated collision domains per port.

Which IEEE standard defines VLAN tagging on Ethernet trunk links?

• a.802.1Q✓
• b.802.11ac
• c.802.1X
• d.802.3af

IEEE 802.1Q defines the frame tagging method used to carry multiple VLANs across a trunk link. 802.3af covers PoE, 802.11ac is Wi-Fi, and 802.1X is port-based access control. The 802.1Q tag adds a 4-byte field to the Ethernet frame.

What is the purpose of a default gateway on a host's IP configuration?

• a.To resolve domain names into IP addresses
• b.To encrypt outbound traffic automatically
• c.To assign IP addresses to other hosts
• d.To forward traffic destined for remote networks✓

The default gateway is the router interface a host uses to reach destinations outside its local subnet. Without it, a host can only communicate on its own network. Traffic for remote networks is sent to the gateway for further routing.

Which frequency band and standard pairing offers wider channels and higher throughput but shorter range?

• a.2.4 GHz with 802.11g
• b.2.4 GHz with 802.11b
• c.900 MHz with 802.11ah
• d.5 GHz with 802.11ac✓

802.11ac operates in the 5 GHz band, offering wider channels and higher throughput at the cost of shorter range and less obstacle penetration. The 2.4 GHz band travels farther but is more congested and slower. Band selection balances speed against coverage.

Which protocol uses TCP port 22 to provide encrypted remote command-line access?

• a.SSH✓
• b.FTP
• c.RDP
• d.Telnet

SSH uses TCP port 22 to provide an encrypted remote shell, replacing insecure protocols like Telnet. Telnet on port 23 sends data in clear text. SSH is the standard for secure device management.

In a client-server architecture, what best describes the role of the server?

• a.It exclusively resolves MAC addresses to IPs
• b.It provides resources or services in response to client requests✓
• c.It only forwards broadcast traffic between subnets
• d.It generates spanning-tree topology changes

A server centrally provides resources or services such as files, web pages, or databases in response to client requests. Clients initiate requests and consume those services. This model contrasts with peer-to-peer where nodes act as both.

Which address is reserved as the IPv4 loopback used to test the local TCP/IP stack?

• a.10.0.0.1
• b.127.0.0.1✓
• c.255.255.255.255
• d.192.168.0.1

127.0.0.1 is the loopback address that lets a host test its own TCP/IP stack without touching the physical network. The entire 127.0.0.0/8 block is reserved for loopback. Pinging it confirms the local protocol stack is functioning.

An administrator is terminating a straight-through Ethernet cable using the T568B standard on both ends. Which pin arrangement starts the sequence?

• a.Orange, white-orange, green, white-green
• b.White-green, green, white-orange, blue
• c.White-brown, brown, white-blue, green
• d.White-orange, orange, white-green, blue✓

The T568B wiring order begins with white-orange, orange, white-green, blue on pins one through four. Using the same standard on both ends creates a straight-through cable. Mixing T568A and T568B on opposite ends creates a crossover.

Which technology allows a switch to supply electrical power to devices such as IP phones and access points over the data cable?

• a.STP
• b.PoE✓
• c.NAT
• d.QoS

Power over Ethernet (PoE) delivers electrical power and data over the same twisted-pair cable, powering devices like IP phones, cameras, and access points. This removes the need for separate power adapters. Standards include 802.3af, 802.3at, and 802.3bt.

When implementing inter-VLAN routing on a single router interface, what configuration is required?

• a.Router-on-a-stick using subinterfaces with 802.1Q tagging✓
• b.A separate physical router for each VLAN
• c.Assigning every VLAN the same subnet
• d.Disabling all trunk links to the switch

Router-on-a-stick uses a single physical interface divided into subinterfaces, each tagged for a VLAN with 802.1Q, to route between VLANs. This avoids needing one physical interface per VLAN. A Layer 3 switch is an alternative that uses SVIs.

A wireless network must support the highest client density in a crowded office. Which deployment choice best reduces co-channel interference on 2.4 GHz?

• a.Use overlapping channels 1, 2, and 3
• b.Increase transmit power to maximum on all APs
• c.Use non-overlapping channels 1, 6, and 11✓
• d.Set every access point to channel 6

In the 2.4 GHz band, channels 1, 6, and 11 are the only non-overlapping options, so alternating them between adjacent APs minimizes co-channel and adjacent-channel interference. Maxing transmit power actually worsens interference. Proper channel planning is key to dense deployments.

Which routing protocol is a link-state interior gateway protocol that uses cost based on bandwidth as its metric?

• a.BGP
• b.EIGRP
• c.OSPF✓
• d.RIP

OSPF is a link-state interior gateway protocol that calculates the shortest path using a cost metric derived from link bandwidth. RIP uses hop count and BGP is a path-vector exterior protocol. OSPF converges faster than distance-vector protocols in large networks.

An engineer configures a static route of last resort. Which destination and mask represent the default route?

• a.127.0.0.0/8
• b.255.255.255.255/32
• c.169.254.0.0/16
• d.0.0.0.0/0✓

The default route is written as 0.0.0.0/0, matching any destination not covered by a more specific route. It directs otherwise-unmatched traffic to a next hop, often the internet gateway. This is commonly called the gateway of last resort.

Which protocol prevents Layer 2 switching loops by placing redundant links into a blocking state?

• a.Hot Standby Router Protocol
• b.Network Time Protocol
• c.Spanning Tree Protocol✓
• d.Border Gateway Protocol

Spanning Tree Protocol (STP) detects redundant Layer 2 paths and blocks them to prevent broadcast storms and switching loops. If an active link fails, a blocked link can transition to forwarding. STP is essential in networks with redundant switch links.

A technician needs to connect two buildings 800 meters apart with high bandwidth and immunity to electromagnetic interference. Which medium is best?

• a.Coaxial cable
• b.Single-mode fiber✓
• c.Cat 6 UTP
• d.Cat 5e UTP

Single-mode fiber supports long distances well beyond copper's 100-meter limit and is immune to electromagnetic interference. Twisted-pair copper cannot reach 800 meters. Fiber is the standard choice for building-to-building backbone links.

Which addressing technique allows many internal private hosts to share a single public IP address for internet access?

• a.ARP
• b.PAT✓
• c.DHCP
• d.VLSM

Port Address Translation (PAT), a form of NAT overload, lets multiple private hosts share one public IP by tracking unique source port numbers. This conserves scarce public IPv4 addresses. Each session is distinguished by its translated port.

When configuring a trunk between two switches, which VLAN carries untagged traffic by default?

• a.The management VLAN only
• b.VLAN 4094
• c.The native VLAN✓
• d.The voice VLAN

The native VLAN carries untagged traffic across an 802.1Q trunk. By default it is VLAN 1, but it should be changed and matched on both ends for security. Mismatched native VLANs can cause connectivity and security problems.

Which wireless security standard introduces Simultaneous Authentication of Equals (SAE) to replace the pre-shared key handshake?

• a.WPA
• b.WEP
• c.WPA2
• d.WPA3✓

WPA3 replaces the WPA2 four-way handshake with SAE, providing stronger protection against offline dictionary attacks. WEP and the original WPA are outdated and insecure. WPA3 is the current recommended standard for wireless security.

A network requires automatic failover of the default gateway between two routers. Which category of protocol provides this?

• a.Address resolution protocol
• b.Spanning tree protocol
• c.First hop redundancy protocol✓
• d.Link aggregation protocol

First hop redundancy protocols such as HSRP, VRRP, and GLBP provide a virtual gateway IP shared by multiple routers for automatic failover. If the active router fails, a standby takes over transparently to hosts. This eliminates the gateway as a single point of failure.

Which technology bundles multiple physical links into one logical link to increase bandwidth and provide redundancy between switches?

• a.Spanning tree
• b.VLAN trunking
• c.Link aggregation (LACP)✓
• d.Port mirroring

Link aggregation, often using LACP (802.3ad), combines several physical ports into a single logical link for greater bandwidth and redundancy. If one member link fails, traffic continues over the others. It is commonly used on switch uplinks and server connections.

An administrator assigns 192.168.1.0/24 but needs subnets of varying host sizes. Which technique allows different subnet mask lengths within the same address block?

• a.VLSM✓
• b.APIPA
• c.Classful addressing
• d.CIDR summarization

Variable Length Subnet Masking (VLSM) lets an administrator apply different mask lengths to subnets within the same network, matching each subnet's host requirement. This conserves address space compared with fixed-size subnets. VLSM requires classless routing protocols.

Which DHCP component defines the range of IP addresses a server can lease to clients?

• a.Scope✓
• b.Exclusion
• c.Reservation
• d.Relay

A DHCP scope defines the pool of addresses available for lease on a given subnet. Reservations assign fixed addresses to specific MACs, and exclusions remove addresses from the pool. Relays forward DHCP requests across subnets.

A technician must extend a wired network into an area where running new cable is impractical. Which device bridges two network segments over the existing electrical wiring?

• a.A powerline (Ethernet-over-power) adapter✓
• b.A loopback plug
• c.A KVM switch
• d.A media converter

Powerline adapters, also called Ethernet-over-power, transmit network data over a building's existing electrical wiring to bridge segments. This avoids running new Ethernet cable. Performance varies with wiring quality and distance.

Which SDN plane is responsible for making forwarding decisions and building the network's logical topology?

• a.Data plane
• b.Management plane
• c.Physical plane
• d.Control plane✓

In software-defined networking, the control plane makes forwarding decisions and maintains the logical topology, then programs the data plane. Separating these planes centralizes intelligence in an SDN controller. The data plane simply forwards packets based on control-plane instructions.

An engineer configures a switch port that should immediately transition to forwarding for a single end host. Which STP feature is appropriate?

• a.Root guard
• b.Trunk negotiation
• c.BPDU flooding
• d.PortFast✓

PortFast lets an access port skip the listening and learning states and move directly to forwarding, which is safe for ports connected to a single end device. It should not be enabled on ports connected to other switches. BPDU guard is often paired with it for protection.

Which type of NAT maps one private IP address to one dedicated public IP address permanently?

• a.Overloaded NAT
• b.Static NAT✓
• c.Port Address Translation
• d.Dynamic NAT

Static NAT creates a permanent one-to-one mapping between a private and a public address, often used to expose an internal server. Dynamic NAT pulls from a pool, and PAT overloads a single public IP. Static NAT provides consistent inbound reachability.

Which protocol allows network devices to be monitored and managed by collecting metrics such as interface counters and CPU usage?

• a.TFTP
• b.NTP
• c.SNMP✓
• d.SMTP

SNMP (Simple Network Management Protocol) polls and collects metrics like interface statistics and CPU usage from managed devices. SNMPv3 adds authentication and encryption over earlier versions. It is a foundational tool for network monitoring systems.

An organization wants a centralized record of events from all network devices for correlation and alerting. Which system aggregates these logs?

• a.RADIUS server
• b.DHCP server
• c.DNS resolver
• d.Syslog server✓

A syslog server centralizes log messages from many devices, enabling correlation, retention, and alerting. Consistent timestamps from NTP make correlation reliable. SIEM platforms often ingest syslog data for security analysis.

Why is accurate time synchronization across network devices important for operations?

• a.It replaces the need for DNS resolution
• b.It increases available interface bandwidth
• c.It eliminates the need for routing protocols
• d.It ensures log timestamps align for accurate event correlation✓

Accurate time via NTP ensures that log entries from different devices share a consistent timeline, which is critical for correlating events during troubleshooting or security investigations. Without synchronized clocks, reconstructing an incident becomes difficult. NTP typically uses UDP port 123.

Which metric describes the variation in packet delay that can degrade real-time voice and video quality?

• a.Jitter✓
• b.Attenuation
• c.Bandwidth
• d.Throughput

Jitter is the variation in delay between received packets and is especially harmful to real-time applications like VoIP and video. Buffers can absorb small amounts of jitter, but excessive jitter causes choppy audio. QoS policies help minimize it.

An administrator wants to prioritize voice traffic over bulk file transfers on a congested link. Which mechanism should be configured?

• a.Port mirroring
• b.Quality of Service (QoS)✓
• c.Jumbo frames
• d.Spanning tree

Quality of Service (QoS) classifies and prioritizes traffic so latency-sensitive flows like voice receive preferential treatment during congestion. Marking and queuing ensure critical traffic is served first. Without QoS, all traffic competes equally.

Which document records the physical and logical layout of network cabling, ports, and connections for reference during maintenance?

• a.Network topology diagram✓
• b.Incident response plan
• c.Acceptable use policy
• d.Service level agreement

A network topology diagram documents devices, cabling, and connections, serving as a reference during maintenance and troubleshooting. Keeping it current speeds fault isolation. Physical and logical diagrams may be maintained separately.

What is the primary purpose of establishing a performance baseline for a network?

• a.To replace the need for monitoring tools
• b.To permanently cap the maximum throughput of links
• c.To assign static IP addresses to servers
• d.To define normal behavior so anomalies can be detected✓

A baseline captures normal metrics such as utilization, latency, and error rates so that deviations signaling problems can be identified. Comparing current data against the baseline speeds anomaly detection. Baselines should be updated as the network evolves.

Which agreement defines the guaranteed uptime and response times a service provider commits to deliver?

• a.MOU
• b.SLA✓
• c.AUP
• d.NDA

A Service Level Agreement (SLA) specifies measurable commitments such as guaranteed uptime and response times between a provider and customer. Failing to meet an SLA may trigger penalties or credits. SLAs guide operational priorities and escalation.