WGU C172 Network and
Security Foundations
2025/2026 – Verified
Questions & Full Rationales |
Real Exam
Section 1: Networking Models (OSI and TCP/IP) (Questions
1-20)
1. In the OSI model, which layer is responsible for routing packets across networks using
logical addressing? A. Layer 1: Physical B. Layer 2: Data Link C. Layer 3: Network D.
Layer 4: Transport
C. Layer 3: Network
Rationale: The Network layer (Layer 3) handles logical addressing (e.g., IP addresses) and
routing decisions to forward packets between networks, using protocols like IP. This
distinguishes it from Data Link (Layer 2, MAC addresses, local delivery) and ensures end -to-end
connectivity in diverse topologies.
2. The TCP/IP model maps most closely to which OSI layer for its Transport function? A.
OSI Layer 3 B. OSI Layer 4 C. OSI Layer 5 D. OSI Layer 7
B. OSI Layer 4
Rationale: TCP/IP's Transport layer (e.g., TCP/UDP) aligns with OSI Layer 4, managing end -
to-end data delivery, error checking, and flow control. This correspondence allows
interoperability, with TCP/IP's simpler 4-layer model streamlining practical implementations
over OSI's 7-layer theoretical framework.
3. Encapsulation in the OSI model occurs as data moves from Layer 7 to Layer 1 by adding:
A. Headers only at each layer B. Trailers at the physical layer C. Headers and trailers at
Data Link D. All of the above
D. All of the above
,Rationale: Encapsulation wraps data with protocol-specific headers (e.g., TCP header at
Transport) and trailers (e.g., FCS at Data Link), enabling layered communication. De-
encapsulation reverses this at the receiver, ensuring reliable transmission across the model.
4. Which OSI layer handles error detection and correction for frames on the same network?
A. Layer 1 B. Layer 2 C. Layer 3 D. Layer 4
B. Layer 2
Rationale: The Data Link layer (Layer 2) uses CRC for error detection in frames and
mechanisms like ARQ for correction, ensuring reliable local delivery before handing off to
Network layer for routing.
5. The Session layer (Layer 5) in OSI is responsible for: A. Establishing and terminating
connections B. Routing data packets C. Physical transmission D. Application data
formatting
A. Establishing and terminating connections
Rationale: Layer 5 manages dialog control, synchronization, and session recovery (e.g.,
checkpoints), distinguishing it from Transport (end-to-end) and Presentation (data translation).
6. In the TCP/IP model, the Internet layer corresponds to OSI's: A. Layers 1 and 2 B. Layer
3 C. Layers 3 and 4 D. Layer 5
B. Layer 3
Rationale: TCP/IP Internet layer (IP) matches OSI Network, focusing on logical addressing and
routing, enabling packet forwarding across internetworks.
7. The Presentation layer (Layer 6) handles: A. Encryption and compression B. Session
management C. Network addressing D. Bit transmission
A. Encryption and compression
Rationale: Layer 6 translates data formats (e.g., ASCII to EBCDIC, JPEG compression),
ensuring application compatibility, separate from Application (user interface).
8. PDU at the Transport layer is called a: A. Frame B. Packet C. Segment or datagram D.
Bit
C. Segment or datagram
Rationale: Transport PDUs are segments (TCP) or datagrams (UDP), encapsulating Network
packets with port numbers for multiplexing.
, 9. The Physical layer (Layer 1) deals with: A. MAC addresses B. IP addresses C. Bits and
electrical signals D. Protocols like HTTP
C. Bits and electrical signals
Rationale: Layer 1 transmits raw bits over media (e.g., cables, signals), defining connectors and
standards like Ethernet cabling.
10. Convergence in networking models refers to: A. OSI and TCP/IP aligning functions B.
Packet loss C. Bandwidth increase D. Latency reduction
A. OSI and TCP/IP aligning functions
Rationale: OSI's 7 layers map to TCP/IP's 4-5, allowing conceptual (OSI) and practical
(TCP/IP) use in modern networks.
11. The Network layer protocol ICMP is used for: A. Error reporting and diagnostics B.
Reliable data transfer C. Application services D. Physical cabling
A. Error reporting and diagnostics
Rationale: ICMP (e.g., ping) provides feedback like unreachable hosts, supporting
troubleshooting in Layer 3.
12. In OSI, the Application layer interacts with: A. End -user software B. Hardware interfaces
C. Routing tables D. MAC sublayer
A. End-user software
Rationale: Layer 7 provides network services to apps (e.g., email protocols), distinct from
Presentation (format).
13. The Data Link layer is divided into: A. Logical and physical sublayers B. LLC and MAC
sublayers C. Transport and network D. Session and presentation
B. LLC and MAC sublayers
Rationale: LLC (flow/error control) and MAC (framing/addressing), enabling standards like
Ethernet.
14. TCP/IP's Link layer encompasses OSI: A. Layers 1 and 2 B. Layer 3 C. Layers 4-7 D.
Layer 7 only
A. Layers 1 and 2
Rationale: Handles physical transmission and local delivery, including Ethernet and PPP.
Security Foundations
2025/2026 – Verified
Questions & Full Rationales |
Real Exam
Section 1: Networking Models (OSI and TCP/IP) (Questions
1-20)
1. In the OSI model, which layer is responsible for routing packets across networks using
logical addressing? A. Layer 1: Physical B. Layer 2: Data Link C. Layer 3: Network D.
Layer 4: Transport
C. Layer 3: Network
Rationale: The Network layer (Layer 3) handles logical addressing (e.g., IP addresses) and
routing decisions to forward packets between networks, using protocols like IP. This
distinguishes it from Data Link (Layer 2, MAC addresses, local delivery) and ensures end -to-end
connectivity in diverse topologies.
2. The TCP/IP model maps most closely to which OSI layer for its Transport function? A.
OSI Layer 3 B. OSI Layer 4 C. OSI Layer 5 D. OSI Layer 7
B. OSI Layer 4
Rationale: TCP/IP's Transport layer (e.g., TCP/UDP) aligns with OSI Layer 4, managing end -
to-end data delivery, error checking, and flow control. This correspondence allows
interoperability, with TCP/IP's simpler 4-layer model streamlining practical implementations
over OSI's 7-layer theoretical framework.
3. Encapsulation in the OSI model occurs as data moves from Layer 7 to Layer 1 by adding:
A. Headers only at each layer B. Trailers at the physical layer C. Headers and trailers at
Data Link D. All of the above
D. All of the above
,Rationale: Encapsulation wraps data with protocol-specific headers (e.g., TCP header at
Transport) and trailers (e.g., FCS at Data Link), enabling layered communication. De-
encapsulation reverses this at the receiver, ensuring reliable transmission across the model.
4. Which OSI layer handles error detection and correction for frames on the same network?
A. Layer 1 B. Layer 2 C. Layer 3 D. Layer 4
B. Layer 2
Rationale: The Data Link layer (Layer 2) uses CRC for error detection in frames and
mechanisms like ARQ for correction, ensuring reliable local delivery before handing off to
Network layer for routing.
5. The Session layer (Layer 5) in OSI is responsible for: A. Establishing and terminating
connections B. Routing data packets C. Physical transmission D. Application data
formatting
A. Establishing and terminating connections
Rationale: Layer 5 manages dialog control, synchronization, and session recovery (e.g.,
checkpoints), distinguishing it from Transport (end-to-end) and Presentation (data translation).
6. In the TCP/IP model, the Internet layer corresponds to OSI's: A. Layers 1 and 2 B. Layer
3 C. Layers 3 and 4 D. Layer 5
B. Layer 3
Rationale: TCP/IP Internet layer (IP) matches OSI Network, focusing on logical addressing and
routing, enabling packet forwarding across internetworks.
7. The Presentation layer (Layer 6) handles: A. Encryption and compression B. Session
management C. Network addressing D. Bit transmission
A. Encryption and compression
Rationale: Layer 6 translates data formats (e.g., ASCII to EBCDIC, JPEG compression),
ensuring application compatibility, separate from Application (user interface).
8. PDU at the Transport layer is called a: A. Frame B. Packet C. Segment or datagram D.
Bit
C. Segment or datagram
Rationale: Transport PDUs are segments (TCP) or datagrams (UDP), encapsulating Network
packets with port numbers for multiplexing.
, 9. The Physical layer (Layer 1) deals with: A. MAC addresses B. IP addresses C. Bits and
electrical signals D. Protocols like HTTP
C. Bits and electrical signals
Rationale: Layer 1 transmits raw bits over media (e.g., cables, signals), defining connectors and
standards like Ethernet cabling.
10. Convergence in networking models refers to: A. OSI and TCP/IP aligning functions B.
Packet loss C. Bandwidth increase D. Latency reduction
A. OSI and TCP/IP aligning functions
Rationale: OSI's 7 layers map to TCP/IP's 4-5, allowing conceptual (OSI) and practical
(TCP/IP) use in modern networks.
11. The Network layer protocol ICMP is used for: A. Error reporting and diagnostics B.
Reliable data transfer C. Application services D. Physical cabling
A. Error reporting and diagnostics
Rationale: ICMP (e.g., ping) provides feedback like unreachable hosts, supporting
troubleshooting in Layer 3.
12. In OSI, the Application layer interacts with: A. End -user software B. Hardware interfaces
C. Routing tables D. MAC sublayer
A. End-user software
Rationale: Layer 7 provides network services to apps (e.g., email protocols), distinct from
Presentation (format).
13. The Data Link layer is divided into: A. Logical and physical sublayers B. LLC and MAC
sublayers C. Transport and network D. Session and presentation
B. LLC and MAC sublayers
Rationale: LLC (flow/error control) and MAC (framing/addressing), enabling standards like
Ethernet.
14. TCP/IP's Link layer encompasses OSI: A. Layers 1 and 2 B. Layer 3 C. Layers 4-7 D.
Layer 7 only
A. Layers 1 and 2
Rationale: Handles physical transmission and local delivery, including Ethernet and PPP.
