A company deploys a VPN solution. At which OSI layer does the VPN primarily encrypt data before transmission?
Answer: C
VPNs perform encryption/decryption at the Presentation Layer, though some VPN implementations also work at Layer 3 for IP-level protection.
Q.22Medium
During a network troubleshooting session, a technician finds that DNS resolution fails while DHCP assignment succeeds. Which layers are functioning and which is failing?
Answer: C
DHCP (Layer 4) works, so Layers 1-4 are functional. DNS resolution failure indicates an issue at the Application Layer (Layer 7) or network configuration.
Q.23Medium
A firewall is configured to block traffic on specific ports. At which minimum OSI layer must the firewall operate to enforce this rule?
Answer: B
Port-based filtering requires inspection at the Transport Layer (Layer 4) where ports (TCP/UDP) are defined and identified.
Q.24Medium
In a complex network architecture, data flows through multiple devices: modem → switch → router → firewall → server. Which device primarily operates at Layer 3?
Answer: C
Routers operate at Layer 3 (Network Layer) to route packets based on IP addresses, while other devices operate at lower layers.
Q.25Medium
A developer needs to ensure data compression before transmission over a network. Which OSI layer should handle this function?
Answer: B
The Presentation Layer (Layer 6) handles data formatting, compression, encryption, and translation between different data formats. It prepares data for transmission.
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Q.26Medium
Which of the following is NOT a function of the Physical Layer in the OSI model?
Answer: C
The Physical Layer (Layer 1) handles physical transmission media and signals, not logical connections. Logical connections are managed by higher layers like the Data Link Layer.
Q.27Medium
In a network troubleshooting scenario, a technician finds that devices cannot communicate despite having correct IP addresses. The issue is at the layer responsible for converting IP addresses to MAC addresses. Which OSI layer is involved?
Answer: B
The Network Layer (Layer 3) uses ARP (Address Resolution Protocol) to map IP addresses to MAC addresses. This is essential for local network communication. The issue suggests an ARP problem at Layer 3.
Q.28Medium
An organization experiences issues with email delivery. The protocol SMTP operates at which OSI layer?
Answer: D
SMTP (Simple Mail Transfer Protocol) is an Application Layer (Layer 7) protocol. All email, web browsing, and user-facing application protocols operate at Layer 7.
Q.29Medium
During a network analysis, it is observed that frames are being retransmitted at a specific layer due to collision detection. Which layer implements CSMA/CD (Carrier Sense Multiple Access/Collision Detection)?
Answer: B
CSMA/CD is implemented at the Data Link Layer (Layer 2), specifically in Ethernet technology. It detects collisions and handles frame retransmission at the local network level.
Q.30Medium
Which of the following best describes the relationship between the OSI model and TCP/IP model?
Answer: B
The TCP/IP model has 4-5 layers compared to OSI's 7 layers. TCP/IP combines several OSI layers. OSI is a conceptual model while TCP/IP is the practical model used in real networks.
Q.31Medium
Consider a scenario where a web server responds to a client request. Trace the data flow: which layer encapsulates the HTTP response into segments before transmission?
Answer: B
The HTTP response originates at Layer 7 (Application), but the Transport Layer (Layer 4) encapsulates it into TCP segments or UDP datagrams. This is the proper encapsulation step at Layer 4.
Q.32Medium
In the context of the OSI model, which layer is responsible for ensuring reliable, in-order delivery of data?
Answer: B
The Transport Layer (Layer 4) provides reliable, in-order delivery through TCP. UDP at this layer provides unreliable delivery. Reliability mechanisms like sequence numbers and acknowledgments operate here.
Q.33Medium
Which protocol operates at the Data Link Layer and is primarily used in Ethernet networks?
Answer: C
MAC and 802.3 standards operate at the Data Link Layer (Layer 2). They define how devices access and share Ethernet transmission media using MAC addresses.
Q.34Medium
A network administrator needs to implement a solution that translates character encoding formats between different systems. Which OSI layer provides this functionality?
Answer: B
The Presentation Layer (Layer 6) handles data translation, character encoding/decoding, encryption, and data format conversions. It ensures data from the sender is in a format the receiver can understand.
Q.35Medium
The TCP/IP model has 4 layers, while the OSI model has 7 layers. Which OSI layers are combined into the TCP/IP Application Layer?
Answer: A
The TCP/IP Application Layer combines the OSI Session Layer (5), Presentation Layer (6), and Application Layer (7).
Q.36Medium
Which protocol operates at the Transport Layer and is connectionless?
Answer: B
UDP (User Datagram Protocol) is a connectionless protocol at Layer 4 that sends data without establishing a connection.
Q.37Medium
In the OSI model, what does the Presentation Layer primarily do?
Answer: B
The Presentation Layer (Layer 6) handles data translation, compression, and encryption for proper data representation.
Q.38Medium
A technician notices that devices can ping each other but cannot access web services. At which OSI layer might the problem exist?
Answer: C
If ping works (Layer 3) but web services don't, the issue is likely at the Application Layer (Layer 7) where HTTP operates.
Q.39Medium
Which OSI layer is responsible for managing access to the shared physical medium?
Answer: B
The Data Link Layer (Layer 2) controls access to the physical medium through MAC addresses and protocols like CSMA/CD.
Q.40Medium
During network troubleshooting, a frame is found to have an incorrect FCS (Frame Check Sequence). At which layer would this be detected and corrected?
Answer: B
FCS is used at the Data Link Layer (Layer 2) to detect errors in frame transmission. Frames with bad FCS are typically discarded.
