Cisco CCNA OSI and TCP/IP Models Questions and Answers — Questions and Answers
Question 1: A network technician is troubleshooting an issue where a user can access local network resources but not websites on the internet. The technician suspects a problem with logical addressing. At which layer of the OSI model does this type of addressing occur?
- Transport Layer
- Network Layer (Correct answer)
- Data Link Layer
- Application Layer
Correct answer: Network Layer
The Network Layer (Layer 3) of the OSI model is responsible for logical addressing, such as IP addresses, which are used to route packets across different networks. Path determination and forwarding between networks happen at this layer. The Data Link Layer uses physical addresses (MAC addresses) for local network communication. The Transport Layer handles end-to-end communication and data segmentation, while the Application Layer provides services to end-user applications.
Question 2: Which of the following correctly identifies the Protocol Data Unit (PDU) at the OSI Transport Layer?
- Packet
- Frame
- Segment (Correct answer)
- Bits
Correct answer: Segment
The Protocol Data Unit (PDU) at the Transport Layer (Layer 4) is called a segment when using TCP, or a datagram when using UDP. Packets are the PDU for the Network Layer (Layer 3), Frames are for the Data Link Layer (Layer 2), and Bits are for the Physical Layer (Layer 1).
Question 3: A web browser uses the HTTP protocol to request a webpage. In the TCP/IP model, which layer is responsible for the functions performed by the Application, Presentation, and Session layers of the OSI model?
- Internet Layer
- Transport Layer
- Network Access Layer
- Application Layer (Correct answer)
Correct answer: Application Layer
The TCP/IP model's Application Layer consolidates the functions of the top three layers of the OSI model: Application, Presentation, and Session. This layer is responsible for protocols like HTTP, FTP, and SMTP that interface directly with user applications.
Question 4: During the data encapsulation process, which layer of the OSI model is responsible for adding a header that contains source and destination MAC addresses?
- Network Layer
- Data Link Layer (Correct answer)
- Physical Layer
- Transport Layer
Correct answer: Data Link Layer
The Data Link Layer (Layer 2) is responsible for creating frames. During encapsulation, it adds a header containing the source and destination MAC (physical) addresses to the packet received from the Network Layer. This framing is essential for delivery on the local network segment.
Question 5: A network administrator is configuring a multilayer switch to perform routing between VLANs. This device primarily operates at which two layers of the OSI model?
- Layer 1 and Layer 2
- Layer 3 and Layer 4
- Layer 2 and Layer 3 (Correct answer)
- Layer 4 and Layer 7
Correct answer: Layer 2 and Layer 3
A multilayer switch, also known as a Layer 3 switch, combines the functionality of a switch and a router. It performs standard Layer 2 (Data Link) functions like MAC address-based forwarding within a VLAN, and also Layer 3 (Network) functions like IP address-based routing between different VLANs.
Question 6: Which statement accurately compares the TCP/IP model to the OSI model?
- The TCP/IP model is a theoretical reference model, while the OSI model is a practical implementation.
- The TCP/IP model has more layers than the OSI model, providing greater detail.
- The OSI model is a reference model that provides guidelines, whereas the TCP/IP model is a protocol model that describes specific protocols. (Correct answer)
- The Network Access layer of the TCP/IP model maps directly to the Network layer of the OSI model.
Correct answer: The OSI model is a reference model that provides guidelines, whereas the TCP/IP model is a protocol model that describes specific protocols.
The OSI model is a conceptual or reference framework developed to standardize network communication functions. The TCP/IP model, developed by the Department of Defense (DoD), is a protocol suite that defines specific protocols (like TCP and IP) and is the practical model upon which the modern internet is built.
Cisco CCNA OSI and TCP/IP Models Questions and Answers
A network technician is troubleshooting an issue where a user can access local network resources but not websites on the internet.
The technician suspects a problem with logical addressing.
At which layer of the OSI model does this type of addressing occur?