Topic 02 Practice Test 2 covers Physical Interfaces, Ethernet Issues, and TCP/UDP for Cisco Certified Network Associate 200-301 CCNA and maps to objectives 1.3–1.5. For broader exam preparation, review the Cisco CCNA 200-301 Exam Dumps. Every option includes focused technical reasoning explaining both the networking concept and its fit to the scenario.
Question 1
A management connection needs a reliable session in which commands and responses arrive in order. Which transport protocol characteristic is most appropriate? Choose ONE.
- Shared Ethernet media
- Speed or autonegotiation mismatch
- UDP
- TCP
Correct Answer: D
Correct Answer
Answer D is correct because TCP is designed to maintain connection state and ordered delivery. TCP is connection-oriented and uses sequencing, acknowledgments, retransmission, and flow control to provide reliable ordered byte-stream delivery. The required outcome is reliable connection-oriented transport. The role matches.
Incorrect Answers
Answer C is incorrect because UDP is connectionless and provides lightweight datagram transport without built-in acknowledgments, retransmission, or ordered-delivery guarantees. Its proper use differs: It fits latency-sensitive or simple request/response traffic that can tolerate loss or handle reliability elsewhere. This case needs reliable connection-oriented transport. TCP is designed to maintain connection state and ordered delivery. It therefore fails here.
Answer A is incorrect because Hub-based or otherwise shared Ethernet exposes several stations to the same collision domain and shared transmission resource. It fits hub-style half-duplex behavior rather than an isolated two-endpoint Ethernet link. Here, the task is reliable connection-oriented transport. TCP is designed to maintain connection state and ordered delivery. That option misses the required function.
Answer B is incorrect because It is appropriate when the problem begins at Ethernet parameter negotiation, before IP routing or applications are involved. Ethernet interfaces must agree on supported signaling parameters; a forced or incompatible speed setting can break link establishment or negotiation. The case instead needs reliable connection-oriented transport. TCP is designed to maintain connection state and ordered delivery. The roles differ.
Question 2
A monitoring application sends independent updates and implements its own loss tolerance. It does not need transport-level sequencing. Which protocol best matches? Choose ONE.
- Layer 3 routing problem
- UDP
- TCP
- Point-to-point Ethernet link
Correct Answer: B
Correct Answer
Answer B is correct because User Datagram Protocol sends independent datagrams with minimal transport state; reliability and ordering are not supplied by UDP itself. The task requires connectionless datagrams without built-in sequencing guarantees. UDP lets the application send independent datagrams with minimal transport overhead. It is the appropriate choice.
Incorrect Answers
Answer C is incorrect because Transmission Control Protocol establishes a connection and tracks sequence/acknowledgment state so lost data can be retransmitted and delivered in order. Choose TCP when delivery correctness, sequencing, and recovery from loss matter more than minimal latency. Here, the task is connectionless datagrams without built-in sequencing guarantees. UDP lets the application send independent datagrams with minimal transport overhead. That option misses the required function.
Answer D is incorrect because Choose it for direct switch-to-device or switch-to-switch links rather than hub-style shared segments. Dedicated switch-to-host or switch-to-switch Ethernet connections are point-to-point because only the two attached interfaces participate on that link. The case instead needs connectionless datagrams without built-in sequencing guarantees. UDP lets the application send independent datagrams with minimal transport overhead. The roles differ.
Answer A is incorrect because An IP routing issue concerns next-hop and prefix selection; it does not inherently create CRC errors, collisions, or loss of physical carrier. Its proper use differs: Use this diagnosis when packets lack a valid Layer 3 path despite otherwise normal physical connectivity. This case needs connectionless datagrams without built-in sequencing guarantees. UDP lets the application send independent datagrams with minimal transport overhead. It therefore fails here.
Question 3
A network engineer is troubleshooting a DNS service. Ordinary client queries use a connectionless transport in most cases. Which transport protocol is that? Choose ONE.
- UDP
- Shared Ethernet media
- Layer 3 routing problem
- TCP
Correct Answer: A
Correct Answer
Answer A is correct because UDP avoids connection setup and retransmission mechanisms, reducing overhead at the cost of guaranteed delivery and ordering. Standard DNS queries commonly use UDP, even though DNS can also use TCP in specific circumstances. Required outcome: the transport commonly used for normal DNS queries. This option fits.
Incorrect Answers
Answer D is incorrect because It is appropriate when the application expects a reliable byte stream rather than best-effort datagrams. TCP trades additional connection and recovery overhead for reliable, ordered transport with acknowledgments and retransmissions. The case instead needs the transport commonly used for normal DNS queries. Standard DNS queries commonly use UDP, even though DNS can also use TCP in specific circumstances. The roles differ.
Answer C is incorrect because A Layer 3 routing problem affects IP path selection or reachability between networks rather than the electrical or optical integrity of the Ethernet link. Investigate routing when Layer 1/2 counters are clean but IP forwarding or route information is wrong. This case needs the transport commonly used for normal DNS queries. That mismatch rules it out.
Answer B is incorrect because Shared Ethernet media puts multiple stations in one collision domain, historically requiring half-duplex contention mechanisms such as CSMA/CD. It describes a common-medium segment, unlike a dedicated modern switched connection. Here, the task is the transport commonly used for normal DNS queries. Standard DNS queries commonly use UDP, even though DNS can also use TCP in specific circumstances. That option misses the required function.
Question 4
A DNS administrator performs a zone transfer between authoritative servers. Which transport protocol is associated with the reliable session required by that operation? Choose ONE.
- Damaged cable, optic, port, or NIC
- Shared Ethernet media
- TCP
- UDP
Correct Answer: C
Correct Answer
Answer C is correct because Zone transfers use TCP so the transferred data is delivered reliably across the session. TCP is connection-oriented and uses sequencing, acknowledgments, retransmission, and flow control to provide reliable ordered byte-stream delivery. The required outcome is reliable transport for a DNS zone-transfer session. The role matches.
Incorrect Answers
Answer D is incorrect because UDP is connectionless and provides lightweight datagram transport without built-in acknowledgments, retransmission, or ordered-delivery guarantees. Its proper use differs: It fits latency-sensitive or simple request/response traffic that can tolerate loss or handle reliability elsewhere. This case needs reliable transport for a DNS zone-transfer session. Zone transfers use TCP so the transferred data is delivered reliably across the session. It therefore fails here.
Answer A is incorrect because Damaged cabling, optics, connectors, ports, or NIC hardware can corrupt frames and appear as CRC/FCS errors, link flaps, or intermittent Layer 1 faults. It should be investigated when physical error counters rise or the interface repeatedly flaps. Here, the task is reliable transport for a DNS zone-transfer session. Zone transfers use TCP so the transferred data is delivered reliably across the session. That option misses the required function.
Answer B is incorrect because Choose shared media when multiple stations contend within one collision domain. On a shared Ethernet segment, attached devices contend for a common medium instead of receiving isolated full-duplex switch links. The case instead needs reliable transport for a DNS zone-transfer session. Zone transfers use TCP so the transferred data is delivered reliably across the session. The roles differ.
Question 5
A TFTP transfer uses simple request/response datagrams without a TCP connection. Which transport protocol underlies TFTP? Choose ONE.
- UDP
- Layer 3 routing problem
- TCP
- Point-to-point Ethernet link
Correct Answer: A
Correct Answer
Answer A is correct because User Datagram Protocol sends independent datagrams with minimal transport state; reliability and ordering are not supplied by UDP itself. The task requires the connectionless transport used by TFTP. TFTP uses UDP and implements any needed transfer logic at the application layer. It is the appropriate choice.
Incorrect Answers
Answer C is incorrect because Transmission Control Protocol establishes a connection and tracks sequence/acknowledgment state so lost data can be retransmitted and delivered in order. Choose TCP when delivery correctness, sequencing, and recovery from loss matter more than minimal latency. Here, the task is the connectionless transport used by TFTP. TFTP uses UDP and implements any needed transfer logic at the application layer. That option misses the required function.
Answer B is incorrect because Choose Layer 3 troubleshooting when the interface is healthy yet destination prefixes are unreachable due to path information. Routing faults occur above the physical link and involve missing, incorrect, or unusable IP forwarding information. The case instead needs the connectionless transport used by TFTP. TFTP uses UDP and implements any needed transfer logic at the application layer. The roles differ.
Answer D is incorrect because Point-to-point Ethernet gives two interfaces a dedicated link instead of placing multiple stations on one shared transmission medium. Its proper use differs: It is appropriate when the link is isolated between a pair of interfaces. This case needs the connectionless transport used by TFTP. TFTP uses UDP and implements any needed transfer logic at the application layer. It therefore fails here.
Question 6
An SSH administrator expects reliable, ordered delivery for the interactive remote-access session. Which transport protocol supports SSH? Choose ONE.
- Damaged cable, optic, port, or NIC
- TCP
- UDP
- Shared Ethernet media
Correct Answer: B
Correct Answer
Answer B is correct because TCP trades additional connection and recovery overhead for reliable, ordered transport with acknowledgments and retransmissions. SSH runs over TCP because the interactive session requires reliable ordered transport. Required outcome: reliable connection-oriented delivery for remote access. This option fits.
Incorrect Answers
Answer C is incorrect because It is appropriate for best-effort datagrams where timeliness or simplicity outweighs built-in reliable delivery. UDP avoids connection setup and retransmission mechanisms, reducing overhead at the cost of guaranteed delivery and ordering. The case instead needs reliable connection-oriented delivery for remote access. SSH runs over TCP because the interactive session requires reliable ordered transport. The roles differ.
Answer D is incorrect because Hub-based or otherwise shared Ethernet exposes several stations to the same collision domain and shared transmission resource. Its proper use differs: It fits hub-style half-duplex behavior rather than an isolated two-endpoint Ethernet link. This case needs reliable connection-oriented delivery for remote access. SSH runs over TCP because the interactive session requires reliable ordered transport. It therefore fails here.
Answer A is incorrect because Physical media and transceiver defects commonly drive rising CRC/FCS counters or repeated up/down transitions even when IP configuration is unchanged. Choose physical-layer troubleshooting when CRC/FCS or signal symptoms point below Layer 3. Here, the task is reliable connection-oriented delivery for remote access. SSH runs over TCP because the interactive session requires reliable ordered transport. That option misses the required function.
Question 7
A switch port connected to a workstation is full duplex. The interface begins showing collisions. What configuration issue should the engineer investigate first? Choose ONE.
- Duplex mismatch
- Layer 3 routing problem
- UDP
- Speed or autonegotiation mismatch
Correct Answer: A
Correct Answer
Answer A is correct because Collisions should not normally occur on full-duplex Ethernet, so a duplex mismatch is a strong suspect. A duplex mismatch occurs when one Ethernet side operates full duplex and the other half duplex, often producing poor throughput, collisions, and FCS errors. The required outcome is collision symptoms inconsistent with a healthy full-duplex link. The role matches.
Incorrect Answers
Answer D is incorrect because A speed or autonegotiation mismatch occurs when Ethernet peers cannot establish compatible link-speed or negotiation settings. Its proper use differs: It fits symptoms centered on link negotiation or link-up failure rather than Layer 3 forwarding. This case needs collision symptoms inconsistent with a healthy full-duplex link. Collisions should not normally occur on full-duplex Ethernet, so a duplex mismatch is a strong suspect. It therefore fails here.
Answer B is incorrect because Layer 3 path problems can prevent remote-network reachability even while interface state and Ethernet error counters remain normal. It fits IP reachability failures driven by routes, not symptoms that directly identify cabling or Ethernet negotiation. Here, the task is collision symptoms inconsistent with a healthy full-duplex link. Collisions should not normally occur on full-duplex Ethernet, so a duplex mismatch is a strong suspect. That option misses the required function.
Answer C is incorrect because It fits latency-sensitive or simple request/response traffic that can tolerate loss or handle reliability elsewhere. UDP is connectionless and provides lightweight datagram transport without built-in acknowledgments, retransmission, or ordered-delivery guarantees. The case instead needs collision symptoms inconsistent with a healthy full-duplex link. Collisions should not normally occur on full-duplex Ethernet, so a duplex mismatch is a strong suspect. The roles differ.
Question 8
A fiber uplink repeatedly flaps after an optic is damaged. Which root-cause category should be investigated? Choose ONE.
- TCP
- Damaged cable, optic, port, or NIC
- Speed or autonegotiation mismatch
- Layer 3 routing problem
Correct Answer: B
Correct Answer
Answer B is correct because A faulty cable, optic, connector, switch port, or NIC can introduce bit errors or loss of signal, producing frame-check errors and unstable links. The task requires a faulty physical-layer component causing link instability. A damaged optic is part of the physical link and can cause repeated up/down transitions. It is the appropriate choice.
Incorrect Answers
Answer D is incorrect because An IP routing issue concerns next-hop and prefix selection; it does not inherently create CRC errors, collisions, or loss of physical carrier. Use this diagnosis when packets lack a valid Layer 3 path despite otherwise normal physical connectivity. Here, the task is a faulty physical-layer component causing link instability. That mismatch rules it out.
Answer A is incorrect because It fits applications that require reliable ordered delivery and can accept the extra transport overhead. TCP is connection-oriented and uses sequencing, acknowledgments, retransmission, and flow control to provide reliable ordered byte-stream delivery. The case instead needs a faulty physical-layer component causing link instability. A damaged optic is part of the physical link and can cause repeated up/down transitions. The roles differ.
Answer C is incorrect because Incompatible speed or autonegotiation configuration can prevent an Ethernet link from coming up or make physical connectivity unstable. Its proper use differs: Choose it when incompatible interface speed or negotiation settings are the evident physical-layer issue. This case needs a faulty physical-layer component causing link instability. A damaged optic is part of the physical link and can cause repeated up/down transitions. It therefore fails here.
Question 9
A campus must build an 8-km optical uplink between buildings using compatible long-reach Ethernet transceivers. Which fiber type should the design use? Choose ONE.
- Copper twisted-pair Ethernet
- Single-mode fiber
- Shared Ethernet media
- Multimode fiber
Correct Answer: B
Correct Answer
Answer B is correct because Long-reach Ethernet optics commonly use single-mode fiber, whose small core supports a single light path over distances beyond typical multimode links. The distance and long-reach optic requirement align with single-mode fiber rather than typical short-reach multimode or copper access cabling. Required outcome: an 8-km optical Ethernet link with long-reach optics. This option fits.
Incorrect Answers
Answer D is incorrect because Choose multimode for appropriate short-reach optical links rather than long-haul fiber requirements. MMF has a larger core that supports multiple propagation modes and is widely used with short-range optical Ethernet transceivers. The case instead needs an 8-km optical Ethernet link with long-reach optics. The distance and long-reach optic requirement align with single-mode fiber rather than typical short-reach multimode or copper access cabling. The roles differ.
Answer A is incorrect because Access Ethernet over copper sends data as electrical signals through twisted pairs; compatible cabling and ports can simultaneously provide DC power. It is appropriate for supported local Ethernet cable runs rather than a fiber-only distance requirement. This case needs an 8-km optical Ethernet link with long-reach optics. That mismatch rules it out.
Answer C is incorrect because Shared Ethernet media puts multiple stations in one collision domain, historically requiring half-duplex contention mechanisms such as CSMA/CD. It describes a common-medium segment, unlike a dedicated modern switched connection. Here, the task is an 8-km optical Ethernet link with long-reach optics. The distance and long-reach optic requirement align with single-mode fiber rather than typical short-reach multimode or copper access cabling. That option misses the required function.
Question 10
A short optical run in a server room must use existing multimode patch panels and compatible short-reach optics. Which medium should be selected? Choose ONE.
- Layer 3 routing problem
- Copper twisted-pair Ethernet
- Multimode fiber
- Single-mode fiber
Correct Answer: C
Correct Answer
Answer C is correct because The installed plant and optics are explicitly multimode components. Short-reach data-center optical links often use multimode fiber with compatible optics, accepting modal dispersion over the intended shorter distance. The required outcome is compatibility with an installed multimode optical plant. The role matches.
Incorrect Answers
Answer D is incorrect because Single-mode fiber uses a small core that carries one propagation mode and is commonly paired with optics designed for comparatively long reach. Its proper use differs: It fits long building-to-building or provider-style optical runs when the optics support the required distance. This case needs compatibility with an installed multimode optical plant. The installed plant and optics are explicitly multimode components. It therefore fails here.
Answer B is incorrect because Copper twisted-pair Ethernet uses electrical signaling over balanced pairs and can also carry Power over Ethernet on compatible links. It fits ordinary access runs that need electrical Ethernet and possibly PoE within supported distance. Here, the task is compatibility with an installed multimode optical plant. The installed plant and optics are explicitly multimode components. That option misses the required function.
Answer A is incorrect because Investigate routing when Layer 1/2 counters are clean but IP forwarding or route information is wrong. A Layer 3 routing problem affects IP path selection or reachability between networks rather than the electrical or optical integrity of the Ethernet link. The case instead needs compatibility with an installed multimode optical plant. The installed plant and optics are explicitly multimode components. The roles differ.
Question 11
A security camera must receive PoE from the access switch. Which cabling medium is required for the powered Ethernet run? Choose ONE.
- Shared Ethernet media
- Multimode fiber
- Copper twisted-pair Ethernet
- Single-mode fiber
Correct Answer: C
Correct Answer
Answer C is correct because Twisted-pair copper provides electrical Ethernet connectivity and, with supported equipment, can deliver PoE over the same cabling. The task requires a medium with copper conductors capable of carrying DC power. Standard PoE delivers power over copper Ethernet pairs. It is the appropriate choice.
Incorrect Answers
Answer D is incorrect because SMF minimizes modal dispersion by supporting one propagation mode, making it the normal choice for longer optical Ethernet links with suitable transceivers. Choose SMF when reach is the dominant requirement and compatible long-range transceivers are available. Here, the task is a medium with copper conductors capable of carrying DC power. Standard PoE delivers power over copper Ethernet pairs. That option misses the required function.
Answer B is incorrect because It fits shorter optical runs where MMF cabling and matching transceivers are available. Multimode fiber carries multiple light modes and is commonly paired with short-reach optics for links inside buildings or data centers. The case instead needs a medium with copper conductors capable of carrying DC power. Standard PoE delivers power over copper Ethernet pairs. The roles differ.
Answer A is incorrect because On a shared Ethernet segment, attached devices contend for a common medium instead of receiving isolated full-duplex switch links. Its proper use differs: Choose shared media when multiple stations contend within one collision domain. This case needs a medium with copper conductors capable of carrying DC power. Standard PoE delivers power over copper Ethernet pairs. It therefore fails here.
Question 12
A network-management platform sends routine SNMP polling requests where lightweight datagram transport is preferred and the application can retry if a response is lost. Which transport protocol best fits? Choose ONE.
- DNS application behavior
- Layer 3 routing problem
- TCP
- UDP
Correct Answer: D
Correct Answer
Answer D is correct because User Datagram Protocol sends independent datagrams with minimal transport state; reliability and ordering are not supplied by UDP itself. UDP avoids connection setup and lets the management application handle any needed retry behavior, matching routine low-overhead polling. Required outcome: lightweight connectionless transport for routine management polling. This option fits.
Incorrect Answers
Answer C is incorrect because Choose TCP when delivery correctness, sequencing, and recovery from loss matter more than minimal latency. Transmission Control Protocol establishes a connection and tracks sequence/acknowledgment state so lost data can be retransmitted and delivered in order. The case instead needs lightweight connectionless transport for routine management polling. UDP avoids connection setup and lets the management application handle any needed retry behavior, matching routine low-overhead polling. The roles differ.
Answer A is incorrect because DNS illustrates that one application may use both transports: lightweight queries commonly use UDP while some larger or stateful operations use TCP. It is relevant to name-resolution transport selection rather than a generic Ethernet physical fault. This case needs lightweight connectionless transport for routine management polling. That mismatch rules it out.
Answer B is incorrect because Routing faults occur above the physical link and involve missing, incorrect, or unusable IP forwarding information. Choose Layer 3 troubleshooting when the interface is healthy yet destination prefixes are unreachable due to path information. Here, the task is lightweight connectionless transport for routine management polling. UDP avoids connection setup and lets the management application handle any needed retry behavior, matching routine low-overhead polling. That option misses the required function.
Question 13
A switch port reports many CRC errors but routing tables and IP addressing are correct. Which troubleshooting area should be examined first? Choose ONE.
- DNS application behavior
- TCP
- Layer 3 routing problem
- Damaged cable, optic, port, or NIC
Correct Answer: D
Correct Answer
Answer D is correct because CRC errors indicate a link-level integrity problem rather than an IP route selection issue. Damaged cabling, optics, connectors, ports, or NIC hardware can corrupt frames and appear as CRC/FCS errors, link flaps, or intermittent Layer 1 faults. The required outcome is physical corruption of Ethernet frames. The role matches.
Incorrect Answers
Answer C is incorrect because Layer 3 path problems can prevent remote-network reachability even while interface state and Ethernet error counters remain normal. Its proper use differs: It fits IP reachability failures driven by routes, not symptoms that directly identify cabling or Ethernet negotiation. This case needs physical corruption of Ethernet frames. CRC errors indicate a link-level integrity problem rather than an IP route selection issue. It therefore fails here.
Answer B is incorrect because TCP trades additional connection and recovery overhead for reliable, ordered transport with acknowledgments and retransmissions. It is appropriate when the application expects a reliable byte stream rather than best-effort datagrams. Here, the task is physical corruption of Ethernet frames. CRC errors indicate a link-level integrity problem rather than an IP route selection issue. That option misses the required function.
Answer A is incorrect because It shows that the application operation determines whether TCP or UDP is appropriate. DNS normally uses UDP for ordinary queries and responses, while TCP is used for particular cases such as zone transfers or other transport needs. The case instead needs physical corruption of Ethernet frames. CRC errors indicate a link-level integrity problem rather than an IP route selection issue. The roles differ.
Question 14
A user has an active link but performance is extremely poor. One interface is half duplex and the peer is full duplex. Which correction is required? Choose ONE.
- Duplex mismatch
- Damaged cable, optic, port, or NIC
- Speed or autonegotiation mismatch
- Layer 3 routing problem
Correct Answer: A
Correct Answer
Answer A is correct because When Ethernet peers disagree on duplex, the half-duplex side may report collisions while the full-duplex side sees errors or severe performance degradation. The task requires matching duplex settings on both link partners. The observed asymmetry is itself the fault; both ends need compatible duplex negotiation or configuration. It is the appropriate choice.
Incorrect Answers
Answer C is incorrect because Ethernet interfaces must agree on supported signaling parameters; a forced or incompatible speed setting can break link establishment or negotiation. It is appropriate when the problem begins at Ethernet parameter negotiation, before IP routing or applications are involved. Here, the task is matching duplex settings on both link partners. The observed asymmetry is itself the fault; both ends need compatible duplex negotiation or configuration. That option misses the required function.
Answer D is incorrect because Use this diagnosis when packets lack a valid Layer 3 path despite otherwise normal physical connectivity. An IP routing issue concerns next-hop and prefix selection; it does not inherently create CRC errors, collisions, or loss of physical carrier. The case instead needs matching duplex settings on both link partners. The observed asymmetry is itself the fault; both ends need compatible duplex negotiation or configuration. The roles differ.
Answer B is incorrect because Physical media and transceiver defects commonly drive rising CRC/FCS counters or repeated up/down transitions even when IP configuration is unchanged. Its proper use differs: Choose physical-layer troubleshooting when CRC/FCS or signal symptoms point below Layer 3. This case needs matching duplex settings on both link partners. The observed asymmetry is itself the fault; both ends need compatible duplex negotiation or configuration. It therefore fails here.
Question 15
A new copper link does not come up after one end is forced to 100 Mb/s and the other to 1 Gb/s. Which diagnosis best fits? Choose ONE.
- Layer 3 routing problem
- Duplex mismatch
- Speed or autonegotiation mismatch
- TCP
Correct Answer: C
Correct Answer
Answer C is correct because A speed or autonegotiation mismatch occurs when Ethernet peers cannot establish compatible link-speed or negotiation settings. The two interfaces cannot establish the expected physical link at different forced rates. Required outcome: incompatible link speed configuration. This option fits.
Incorrect Answers
Answer B is incorrect because It fits error-heavy, slow Ethernet caused by half/full-duplex disagreement, not an IP route-selection problem. Mismatched half/full-duplex settings can leave link up while causing intermittent delivery, late collisions, CRC/FCS errors, and unexpectedly low throughput. The case instead needs incompatible link speed configuration. The two interfaces cannot establish the expected physical link at different forced rates. The roles differ.
Answer A is incorrect because A Layer 3 routing problem affects IP path selection or reachability between networks rather than the electrical or optical integrity of the Ethernet link. Its proper use differs: Investigate routing when Layer 1/2 counters are clean but IP forwarding or route information is wrong. This case needs incompatible link speed configuration. The two interfaces cannot establish the expected physical link at different forced rates. It therefore fails here.
Answer D is incorrect because TCP is connection-oriented and uses sequencing, acknowledgments, retransmission, and flow control to provide reliable ordered byte-stream delivery. It fits applications that require reliable ordered delivery and can accept the extra transport overhead. Here, the task is incompatible link speed configuration. The two interfaces cannot establish the expected physical link at different forced rates. That option misses the required function.
Question 16
A modern switch port running full duplex is described as having its own collision domain with no media contention from other switch ports. Which connection model best describes the link? Choose ONE.
- Point-to-point Ethernet link
- Duplex mismatch
- Shared Ethernet media
- Layer 3 routing problem
Correct Answer: A
Correct Answer
Answer A is correct because Switched full-duplex Ethernet provides a point-to-point segment rather than a shared collision medium. A point-to-point Ethernet link connects exactly two endpoints across one link; modern switched full-duplex links do not form a shared collision domain. The required outcome is a dedicated Ethernet link between two endpoints. The role matches.
Incorrect Answers
Answer C is incorrect because Hub-based or otherwise shared Ethernet exposes several stations to the same collision domain and shared transmission resource. Its proper use differs: It fits hub-style half-duplex behavior rather than an isolated two-endpoint Ethernet link. This case needs a dedicated Ethernet link between two endpoints. Switched full-duplex Ethernet provides a point-to-point segment rather than a shared collision medium. It therefore fails here.
Answer B is incorrect because A duplex mismatch occurs when one Ethernet side operates full duplex and the other half duplex, often producing poor throughput, collisions, and FCS errors. It is a strong diagnosis when the link remains up but collision/error counters and performance are poor. Here, the task is a dedicated Ethernet link between two endpoints. That mismatch rules it out.
Answer D is incorrect because Choose Layer 3 troubleshooting when the interface is healthy yet destination prefixes are unreachable due to path information. Routing faults occur above the physical link and involve missing, incorrect, or unusable IP forwarding information. The case instead needs a dedicated Ethernet link between two endpoints. Switched full-duplex Ethernet provides a point-to-point segment rather than a shared collision medium. The roles differ.
Question 17
An old half-duplex shared Ethernet segment requires stations to contend for access to the common medium. Which connection type is described? Choose ONE.
- Layer 3 routing problem
- TCP
- Shared Ethernet media
- Point-to-point Ethernet link
Correct Answer: C
Correct Answer
Answer C is correct because Shared Ethernet media puts multiple stations in one collision domain, historically requiring half-duplex contention mechanisms such as CSMA/CD. The task requires a common collision domain shared by multiple devices. Shared media is the environment in which multiple stations contend for the same Ethernet transmission resource. It is the appropriate choice.
Incorrect Answers
Answer D is incorrect because Dedicated switch-to-host or switch-to-switch Ethernet connections are point-to-point because only the two attached interfaces participate on that link. Choose it for direct switch-to-device or switch-to-switch links rather than hub-style shared segments. Here, the task is a common collision domain shared by multiple devices. Shared media is the environment in which multiple stations contend for the same Ethernet transmission resource. That option misses the required function.
Answer B is incorrect because Choose TCP when delivery correctness, sequencing, and recovery from loss matter more than minimal latency. Transmission Control Protocol establishes a connection and tracks sequence/acknowledgment state so lost data can be retransmitted and delivered in order. The case instead needs a common collision domain shared by multiple devices. Shared media is the environment in which multiple stations contend for the same Ethernet transmission resource. The roles differ.
Answer A is incorrect because Layer 3 path problems can prevent remote-network reachability even while interface state and Ethernet error counters remain normal. Its proper use differs: It fits IP reachability failures driven by routes, not symptoms that directly identify cabling or Ethernet negotiation. This case needs a common collision domain shared by multiple devices. Shared media is the environment in which multiple stations contend for the same Ethernet transmission resource. It therefore fails here.
Question 18
A database synchronization service needs flow control, acknowledgments, and retransmission when segments are lost. Which transport protocol provides those mechanisms? Choose ONE.
- Shared Ethernet media
- Damaged cable, optic, port, or NIC
- UDP
- TCP
Correct Answer: D
Correct Answer
Answer D is correct because TCP trades additional connection and recovery overhead for reliable, ordered transport with acknowledgments and retransmissions. TCP includes the reliability and flow-control mechanisms described. Required outcome: reliable stateful transport services. This option fits.
Incorrect Answers
Answer C is incorrect because It is appropriate for best-effort datagrams where timeliness or simplicity outweighs built-in reliable delivery. UDP avoids connection setup and retransmission mechanisms, reducing overhead at the cost of guaranteed delivery and ordering. The case instead needs reliable stateful transport services. TCP includes the reliability and flow-control mechanisms described. The roles differ.
Answer B is incorrect because A faulty cable, optic, connector, switch port, or NIC can introduce bit errors or loss of signal, producing frame-check errors and unstable links. Its proper use differs: It fits faults tied to media, optics, connectors, ports, or NICs rather than route or application logic. This case needs reliable stateful transport services. TCP includes the reliability and flow-control mechanisms described. It therefore fails here.
Answer A is incorrect because On a shared Ethernet segment, attached devices contend for a common medium instead of receiving isolated full-duplex switch links. Choose shared media when multiple stations contend within one collision domain. Here, the task is reliable stateful transport services. TCP includes the reliability and flow-control mechanisms described. That option misses the required function.
Question 19
A custom sensor protocol uses UDP but still needs guaranteed delivery. Where would the additional reliability have to be implemented? Choose ONE.
- UDP
- Layer 3 routing problem
- Speed or autonegotiation mismatch
- TCP
Correct Answer: A
Correct Answer
Answer A is correct because UDP itself does not provide acknowledgments or retransmissions, so the application must add them if required. UDP is connectionless and provides lightweight datagram transport without built-in acknowledgments, retransmission, or ordered-delivery guarantees. The required outcome is connectionless transport that leaves reliability to another layer. The role matches.
Incorrect Answers
Answer D is incorrect because TCP is connection-oriented and uses sequencing, acknowledgments, retransmission, and flow control to provide reliable ordered byte-stream delivery. Its proper use differs: It fits applications that require reliable ordered delivery and can accept the extra transport overhead. This case needs connectionless transport that leaves reliability to another layer. UDP itself does not provide acknowledgments or retransmissions, so the application must add them if required. It therefore fails here.
Answer B is incorrect because An IP routing issue concerns next-hop and prefix selection; it does not inherently create CRC errors, collisions, or loss of physical carrier. Use this diagnosis when packets lack a valid Layer 3 path despite otherwise normal physical connectivity. Here, the task is connectionless transport that leaves reliability to another layer. That mismatch rules it out.
Answer C is incorrect because Choose it when incompatible interface speed or negotiation settings are the evident physical-layer issue. Incompatible speed or autonegotiation configuration can prevent an Ethernet link from coming up or make physical connectivity unstable. The case instead needs connectionless transport that leaves reliability to another layer. UDP itself does not provide acknowledgments or retransmissions, so the application must add them if required. The roles differ.
Question 20
A developer must choose between TCP and UDP for live audio. The application can conceal small packet losses but is sensitive to retransmission delay. Which protocol is the better default choice? Choose ONE.
- Damaged cable, optic, port, or NIC
- Layer 3 routing problem
- UDP
- TCP
Correct Answer: C
Correct Answer
Answer C is correct because User Datagram Protocol sends independent datagrams with minimal transport state; reliability and ordering are not supplied by UDP itself. The task requires low-overhead transport without delayed retransmission. UDP better matches a real-time stream that values timeliness over built-in recovery of every lost packet. It is the appropriate choice.
Incorrect Answers
Answer D is incorrect because Transmission Control Protocol establishes a connection and tracks sequence/acknowledgment state so lost data can be retransmitted and delivered in order. Choose TCP when delivery correctness, sequencing, and recovery from loss matter more than minimal latency. Here, the task is low-overhead transport without delayed retransmission. UDP better matches a real-time stream that values timeliness over built-in recovery of every lost packet. That option misses the required function.
Answer B is incorrect because Investigate routing when Layer 1/2 counters are clean but IP forwarding or route information is wrong. A Layer 3 routing problem affects IP path selection or reachability between networks rather than the electrical or optical integrity of the Ethernet link. The case instead needs low-overhead transport without delayed retransmission. UDP better matches a real-time stream that values timeliness over built-in recovery of every lost packet. The roles differ.
Answer A is incorrect because Damaged cabling, optics, connectors, ports, or NIC hardware can corrupt frames and appear as CRC/FCS errors, link flaps, or intermittent Layer 1 faults. Its proper use differs: It should be investigated when physical error counters rise or the interface repeatedly flaps. This case needs low-overhead transport without delayed retransmission. UDP better matches a real-time stream that values timeliness over built-in recovery of every lost packet. It therefore fails here.
