CCNA Networking Concepts Questions — Page 2 of 2

MCQeasy

A network switch that forwards frames based on MAC addresses operates at which layer of the OSI model?

A.Physical

B.Data Link

C.Network

D.Transport

AnswerB

MAC address forwarding is a Layer 2 function: switches build a MAC address table and forward frames based on destination MAC, which is the Data Link layer's addressing scheme. Layer 3 handles IP routing, so Data Link is the correct OSI layer for this behaviour.

Why this answer

A network switch that forwards frames based on MAC addresses operates at Layer 2, the Data Link layer. This layer is responsible for node-to-node data transfer and error detection using MAC addresses, as defined by IEEE 802 standards. Switches build a MAC address table by learning source MAC addresses from incoming frames and use this table to make forwarding decisions.

Exam trap

The N10-009 exam often tests the misconception that switches operate at Layer 3 because they can be configured with IP addresses for management (e.g., SVI), but the core frame-forwarding function remains at Layer 2 using MAC addresses.

Why the other options are wrong

The Physical layer (Layer 1) handles raw bit transmission over a physical medium, not MAC address-based frame forwarding. A switch that forwards frames using MAC addresses operates at the Data Link layer (Layer 2).

The Network layer (Layer 3) uses logical addressing (e.g., IP addresses) for routing packets between networks, not MAC addresses for forwarding frames within a single network.

The Transport layer (Layer 4) handles end-to-end communication, segmentation, and flow control, not MAC address-based frame forwarding, which is a Layer 2 function.

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MCQmedium

A network engineer is designing a new office network and needs to choose a routing protocol that supports variable-length subnet masks and fast convergence for a small to medium-sized enterprise. The engineer wants a link-state protocol that uses cost as its metric. Which of the following should the engineer select?

A.OSPF

B.BGP

C.RIPv2

D.EIGRP

AnswerA

OSPF is a link-state interior gateway protocol that supports VLSM and uses cost as its metric, typically derived from interface bandwidth. It converges quickly and is well suited for small to medium-sized enterprises. This matches all the stated requirements.

Why this answer

OSPF is a link-state routing protocol that uses cost as its metric and supports VLSM, making it ideal for the described enterprise network. It builds a topological map and runs the Shortest Path First algorithm to converge quickly. RIPv2 is distance-vector with hop count, EIGRP is advanced distance-vector with a composite metric, and BGP is an exterior gateway protocol.

Exam trap

The trap here is confusing EIGRP with a link-state protocol because it converges quickly, but EIGRP is actually an advanced distance-vector protocol.

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Matchingmedium

Match each network protocol to its well-known port number.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

443

3389

Why these pairings

Common well-known ports: HTTP=80, HTTPS=443, FTP=21, SSH=22. The distractors swap these assignments.

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MCQmedium

A network administrator is designing a small office network with 40 workstations. The design must ensure that a single cable failure only affects the connected workstation. Which logical topology should the administrator implement?

A.Star

B.Ring

C.Bus

D.Mesh

AnswerA

The Star topology is ideal for a small office network with 40 workstations because each device connects via a dedicated cable segment to a central networking device, typically a switch. This design offers excellent fault isolation; a failure in one cable or network interface card only impacts that single workstation, leaving the rest of the network operational. Furthermore, adding or removing devices is straightforward, and troubleshooting is simplified due to the centralized connection point, making it highly manageable and scalable for this size.

Why this answer

A star topology connects each workstation directly to a central switch or hub, so a cable failure only affects the single connected workstation, not the rest of the network. This meets the requirement for fault isolation at the workstation level, which is the core design goal in a small office with 40 devices.

Exam trap

CompTIA often tests the distinction between physical and logical topology—candidates may confuse a physical star with a logical bus (e.g., early Ethernet using a hub) and incorrectly assume a cable failure only affects one workstation, but a hub-based star is logically a bus where a collision domain spans all ports, though the physical cable break still isolates only the connected device.

Why the other options are wrong

In a ring topology, each workstation is connected to two neighbors, forming a closed loop. A single cable failure can break the ring, affecting all workstations beyond the break, not just the connected one.

In a bus topology, a single cable failure (the backbone) can disrupt connectivity for multiple workstations, not just the connected workstation, because all devices share the same communication line.

A mesh topology requires multiple connections per workstation, which does not ensure that a single cable failure only affects the connected workstation; in fact, mesh provides redundancy, but a cable failure still only affects the directly connected device, but the design is overkill and not cost-effective for 40 workstations.

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MCQeasy

Which of the following is the primary function of a subnet mask in IPv4 networking?

A.It identifies the default gateway for a subnet

B.It determines the network portion of an IP address

C.It provides encryption for data in transit

D.It maps IP addresses to MAC addresses

AnswerB

The subnet mask is a 32-bit number that, when logically combined with an IP address using a bitwise AND operation, precisely delineates the network portion from the host portion. This fundamental operation allows devices to determine if a destination IP address resides on the local network segment or requires forwarding to a router. By defining the network boundary, the subnet mask is crucial for efficient packet routing decisions within an IPv4 network.

Why this answer

The subnet mask's primary function is to distinguish the network portion from the host portion of an IPv4 address. By applying a bitwise AND operation between the IP address and the subnet mask, the network address is derived, which is essential for routing decisions. Without this separation, devices cannot determine whether a destination is local or requires forwarding through a router.

Exam trap

The trap here is that candidates often confuse the subnet mask's role with that of the default gateway, mistakenly thinking the mask itself identifies the router address, when in fact the mask only defines the network/host boundary and has no direct relationship to gateway configuration.

Why the other options are wrong

The subnet mask does not identify the default gateway; it separates the network and host portions of an IP address. The default gateway is a separate configuration parameter.

Subnet masks do not provide encryption; they are used to divide an IP address into network and host portions. Encryption is a function of protocols like IPsec or TLS, not subnet masks.

The subnet mask does not map IP addresses to MAC addresses; that is the function of ARP (Address Resolution Protocol).

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MCQeasy

Which of the following network protocols operates at the Transport layer of the OSI model and provides connection-oriented, reliable data delivery?

A.UDP

B.TCP

C.IP

D.ARP

AnswerB

TCP (Transmission Control Protocol) is a fundamental connection-oriented protocol operating at the Transport layer (Layer 4) of the OSI model. It ensures reliable, ordered, and error-checked delivery of data segments between applications. TCP achieves this through mechanisms like three-way handshakes for connection establishment, sequence numbers for ordering, acknowledgments for receipt confirmation, flow control to manage data rates, and retransmission of lost or corrupted packets, guaranteeing data integrity.

Why this answer

TCP (Transmission Control Protocol) operates at the Transport layer (Layer 4) of the OSI model and provides connection-oriented, reliable data delivery through mechanisms such as three-way handshake, sequence numbers, acknowledgments, and retransmission of lost segments. This ensures that data is delivered in order and without errors, making TCP the correct choice for the question.

Exam trap

The trap here is that candidates often confuse IP (Network layer) with a transport protocol or mistakenly think UDP provides reliability because it has checksums, but UDP lacks connection setup and retransmission, making TCP the only correct answer for connection-oriented reliable delivery.

Why the other options are wrong

UDP operates at the Transport layer but provides connectionless, unreliable data delivery without acknowledgments or retransmissions, unlike the connection-oriented, reliable delivery specified in the question.

IP operates at the Network layer (Layer 3) of the OSI model, not the Transport layer. It provides connectionless, unreliable datagram delivery, not connection-oriented, reliable data delivery.

ARP operates at the Network layer (Layer 3) of the OSI model, not the Transport layer, and it resolves IP addresses to MAC addresses; it does not provide connection-oriented, reliable data delivery.

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MCQeasy

Which of the following best describes a broadcast domain?

A.All devices connected to the same switch

B.All devices that share the same IP subnet

C.All devices that can receive a broadcast frame from any other device in the network segment

D.All devices that have the same MAC address prefix

AnswerC

A broadcast domain is fundamentally a Layer 2 concept, encompassing all devices that receive a broadcast frame originating from any other device within that same logical segment. Routers typically act as boundaries, preventing broadcasts from traversing into other domains, while switches, within a single VLAN, propagate these frames to all connected ports. This definition precisely captures the scope of network communication where a single broadcast will reach every participant.

Why this answer

A broadcast domain is defined as the set of all devices that can receive a broadcast frame (destination MAC FF:FF:FF:FF:FF:FF) sent by any other device within the same network segment. This boundary is typically enforced by Layer 3 devices like routers, which do not forward broadcast frames, whereas Layer 2 switches forward broadcasts out all ports except the receiving port within the same VLAN.

Exam trap

The trap here is that candidates often confuse a broadcast domain with a collision domain or assume all devices on the same switch are in the same broadcast domain, ignoring VLAN segmentation.

Why the other options are wrong

A broadcast domain is defined by the ability to receive broadcast frames, not by physical connectivity to the same switch. A single switch can be divided into multiple VLANs, each forming a separate broadcast domain, so all devices on the same switch may belong to different broadcast domains.

A broadcast domain is defined by the ability to receive broadcast frames, not by IP subnet membership. Devices in different subnets can be in the same broadcast domain if connected via a bridge or switch without a router.

A broadcast domain is defined by the ability to receive broadcast frames, not by MAC address prefix. MAC address prefixes identify the manufacturer, not broadcast boundaries.

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MCQeasy

Which of the following best describes the function of a default gateway on a host?

A.It forwards packets destined for networks other than the local subnet

B.It resolves domain names to IP addresses

C.It assigns IP addresses to devices on the local network

D.It filters traffic based on MAC addresses

AnswerA

The primary function of a default gateway is to serve as the exit point for all network traffic originating from a host that is destined for a different IP network. When a host needs to send a packet to an IP address outside its local subnet, it encapsulates the packet and forwards it to the default gateway's MAC address on the local segment. The default gateway, typically a router, then takes responsibility for routing that packet towards its ultimate destination across various interconnected networks.

Why this answer

The default gateway is the router interface on the local subnet that a host uses to send packets destined for IP addresses outside its own subnet. When a host determines that the destination IP is not reachable via ARP on the local link, it forwards the packet to the default gateway's MAC address, which then routes the packet toward the remote network. This is essential for inter-subnet communication in any IP network.

Exam trap

The trap here is that candidates often confuse the default gateway with a DNS server or DHCP server, because in many home networks the same device (the router) performs all three roles, but the exam tests the distinct Layer 3 routing function of the default gateway in isolation.

Why the other options are wrong

The default gateway is responsible for routing packets to destinations outside the local subnet, not for resolving domain names to IP addresses. DNS servers perform name resolution.

The default gateway does not assign IP addresses; that is the function of a DHCP server. The default gateway is a router that forwards packets to destinations outside the local subnet.

A default gateway forwards packets to other networks, not filter traffic based on MAC addresses; MAC filtering is a function of switches or security features, not the default gateway.

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MCQeasy

A network administrator needs to connect 10 workstations in a way that each workstation's traffic does not collide with others. Which device should be used to connect these workstations?

A.Hub

B.Switch

C.Router

D.Modem

AnswerB

A switch operates at Layer 2 (Data Link Layer) of the OSI model, learning MAC addresses and forwarding frames only to the intended destination port. This intelligent forwarding creates a dedicated collision domain for each connected device, effectively eliminating collisions within the switch and maximizing bandwidth utilization for each workstation. This is crucial for connecting multiple workstations efficiently without performance degradation.

Why this answer

A switch is the correct device because it operates at Layer 2 of the OSI model, using MAC addresses to forward frames only to the specific destination port. This creates separate collision domains for each connected workstation, ensuring that traffic from one workstation does not collide with traffic from another.

Exam trap

The trap here is that candidates often confuse a hub with a switch, thinking both simply 'connect' devices, but the key differentiator is that a hub creates a single collision domain while a switch creates separate collision domains per port.

Why the other options are wrong

A hub operates at Layer 1 and forwards all traffic to all ports, causing collisions; it does not isolate traffic per workstation.

A router is designed to connect different networks and route traffic between them, not to provide collision-free communication within a single local network. For 10 workstations on the same LAN, a switch is the correct device to eliminate collisions.

A modem modulates/demodulates signals for WAN connections (e.g., DSL, cable) and does not provide collision-free local network switching; it cannot separate traffic between workstations on a LAN.

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MCQeasy

At which OSI layer does a router primarily operate to make forwarding decisions based on IP addresses?

A.Layer 1 (Physical)

B.Layer 2 (Data Link)

C.Layer 3 (Network)

D.Layer 4 (Transport)

AnswerC

A router's primary function is to forward data packets between different network segments or subnets. This crucial operation relies on examining the destination logical IP address contained within the packet header, which is a function of the OSI Layer 3, the Network layer. Routers use routing tables to determine the optimal path for these packets, making intelligent forwarding decisions based on network topology and reachability, fundamentally operating at this layer to connect disparate networks.

Why this answer

A router primarily operates at Layer 3 (Network) of the OSI model because it uses logical IP addresses (e.g., IPv4 or IPv6) to make forwarding decisions. The router examines the destination IP address in the packet header, performs a longest-prefix match against its routing table, and determines the next-hop interface. This layer is responsible for end-to-end delivery and path selection across multiple networks.

Exam trap

CompTIA often tests the misconception that routers operate at Layer 2 because they forward frames, but the key distinction is that routers make forwarding decisions based on Layer 3 IP addresses, not Layer 2 MAC addresses.

Why the other options are wrong

Routers use IP addresses to make forwarding decisions, which operate at Layer 3 (Network). Layer 1 is the physical medium (cables, signals) and does not involve IP addresses.

A router makes forwarding decisions based on IP addresses, which are Layer 3 (Network layer) addresses. Layer 2 (Data Link layer) uses MAC addresses for forwarding within a local network, not IP addresses.

Routers make forwarding decisions based on IP addresses, which operate at Layer 3 (Network). Layer 4 (Transport) handles end-to-end communication and port numbers, not IP routing.

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MCQeasy

Which protocol is used to resolve a known IP address to a corresponding MAC address on a local network?

A.ARP

B.DNS

C.DHCP

D.ICMP

AnswerA

ARP (Address Resolution Protocol) is a Layer 2 protocol responsible for mapping a known Layer 3 IPv4 address to its corresponding Layer 2 MAC (Media Access Control) address within the same local network segment. When a device needs to send data to another host on the same local network and only knows the destination's IP address, it uses ARP to discover the necessary MAC address for direct frame delivery. This process is fundamental for local network communication.

Why this answer

ARP (Address Resolution Protocol) is used to resolve a known IP address to its corresponding MAC address on a local network. When a host needs to send a frame to another host on the same subnet, it broadcasts an ARP request containing the target IP; the host with that IP responds with its MAC address, which is then cached for future use.

Exam trap

The trap here is confusing ARP with DNS, as both involve 'resolution,' but DNS resolves names to IPs (Layer 3) while ARP resolves IPs to MACs (Layer 2), and candidates often forget ARP operates only within a local broadcast domain.

Why the other options are wrong

DNS resolves domain names to IP addresses, not IP addresses to MAC addresses. The question specifically asks for mapping an IP address to a MAC address on a local network, which is ARP's function.

DHCP is used to dynamically assign IP addresses and other network configuration parameters to devices, not to resolve IP addresses to MAC addresses. The resolution of IP to MAC addresses on a local network is performed by ARP.

ICMP is used for network diagnostics (e.g., ping, traceroute) and error reporting, not for resolving IP addresses to MAC addresses. The Address Resolution Protocol (ARP) is the correct protocol for this purpose.

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MCQeasy

Which of the following best describes the primary function of the transport layer in the OSI model?

A.Routing packets across networks

B.Providing end-to-end communication and data flow control

C.Encoding data into electrical signals

D.Determining the best path for data transmission

AnswerB

The transport layer, specifically Layer 4 of the OSI model, is responsible for establishing and maintaining logical end-to-end connections between applications running on different hosts. It manages data segmentation into smaller units, reassembly at the destination, and implements robust flow control mechanisms, such as windowing, to prevent network congestion and ensure that a sender does not overwhelm a receiver. Furthermore, protocols like TCP provide reliable data transfer through acknowledgments and retransmissions, guaranteeing data integrity and ordered delivery.

Why this answer

The transport layer (Layer 4) is responsible for end-to-end communication between hosts, including segmentation, reassembly, and flow control. Protocols like TCP use windowing and acknowledgments to manage data flow, ensuring reliable delivery. This distinguishes it from lower layers that handle routing or physical signaling.

Exam trap

CompTIA often tests the confusion between the transport layer's end-to-end delivery and the network layer's path determination, leading candidates to incorrectly select routing-related options like A or D.

Why the other options are wrong

Routing packets across networks is a function of the network layer (Layer 3), not the transport layer (Layer 4). The transport layer provides end-to-end communication and flow control.

Encoding data into electrical signals is a function of the physical layer, not the transport layer. The transport layer handles end-to-end communication and flow control, not signal encoding.

Determining the best path for data transmission is a function of the network layer (Layer 3), not the transport layer (Layer 4). The transport layer focuses on end-to-end communication and flow control.

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MCQeasy

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

B.Data Link layer

C.Physical layer

D.Network layer

AnswerC

The Physical layer (Layer 1) is fundamentally responsible for the raw bit stream transmission over the physical medium, defining the electrical, mechanical, and procedural specifications for transmitting data signals. Therefore, issues such as faulty cables, damaged connectors, incorrect cable types, or signal degradation due to attenuation or electromagnetic interference directly manifest as problems at this foundational layer, preventing any higher-layer communication from occurring reliably or at all.

Why this answer

The Physical layer (Layer 1) is the correct starting point because the administrator suspects the problem is related to physical cabling. The Physical layer defines the electrical, mechanical, and procedural specifications for transmitting raw bits over a physical medium, such as copper or fiber optic cables. Troubleshooting at this layer involves checking for cable faults, signal degradation, or improper termination before moving up the OSI stack.

Exam trap

The trap here is that candidates often jump to the Data Link layer (Layer 2) because they associate 'connectivity issues' with MAC addresses or switching, forgetting that physical cabling faults must be ruled out first at Layer 1.

Why the other options are wrong

The question specifies a physical cabling issue, which is a Layer 1 (Physical layer) problem. The Transport layer (Layer 4) deals with end-to-end communication and data segmentation, not physical media.

The Data Link layer (Layer 2) handles framing, MAC addressing, and error detection, but not the physical cabling itself. The question specifically states the issue is related to physical cabling, which is Layer 1.

The Network layer (Layer 3) handles logical addressing and routing, not physical cabling issues. The administrator suspects a physical cabling problem, which is a Layer 1 concern.

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