CCST - Cisco Certified Support Technician OSI and TCP/IP Models Questions and Answers 1 — Questions and Answers
Question 1: A network technician is troubleshooting an issue where a user can ping the IP address of a web server but cannot open the website in their browser. At which layer of the OSI model is the problem MOST likely occurring?
- Network Layer
- Transport Layer
- Application Layer (Correct answer)
- Data Link Layer
Correct answer: Application Layer
The ability to successfully ping the server's IP address indicates that connectivity exists at the Network Layer (Layer 3). The problem lies with the web browsing service itself, which operates at the Application Layer (Layer 7). Protocols like HTTP or HTTPS are used for web browsing, and an issue with the server's web service or a firewall blocking these specific protocols would cause this symptom.
Question 2: During the data encapsulation process, which Protocol Data Unit (PDU) is created at the Network Layer of the OSI model?
- Segment
- Frame
- Bits
- Packet (Correct answer)
Correct answer: Packet
At the Network Layer (Layer 3) of the OSI model, data is encapsulated into a PDU called a packet. This packet contains the source and destination IP addresses. Segments are the PDU for the Transport Layer, Frames are for the Data Link Layer, and Bits are transmitted at the Physical Layer.
Question 3: Which layer of the TCP/IP model is responsible for logical addressing and determining the best path for data to travel across the network?
- Application
- Transport
- Internet (Correct answer)
- Network Access
Correct answer: Internet
The Internet layer of the TCP/IP model is responsible for logical addressing (using IP addresses) and routing, which involves selecting the best path for data to travel from the source to the destination network. This layer directly corresponds to the Network Layer of the OSI model.
Question 4: A support technician is investigating a connectivity issue. The user's network cable is properly connected, and the link light on the network interface card (NIC) is green. However, the user cannot access any network resources. Using a bottom-up troubleshooting approach based on the OSI model, what is the NEXT layer the technician should investigate?
- Network Layer
- Data Link Layer (Correct answer)
- Transport Layer
- Physical Layer
Correct answer: Data Link Layer
The technician has already verified the Physical Layer (Layer 1) by checking the cable and the link light. The next step in a bottom-up troubleshooting methodology is to investigate the Data Link Layer (Layer 2). This would involve checking for issues like MAC address problems, VLAN configuration, or switch port status.
Question 5: Which of the following functions is a primary responsibility of the Transport Layer in both the OSI and TCP/IP models?
- Converting data into electrical signals for transmission.
- Providing logical device addressing and path determination.
- Formatting data with encryption and compression.
- Establishing reliable, end-to-end connections using protocols like TCP. (Correct answer)
Correct answer: Establishing reliable, end-to-end connections using protocols like TCP.
The Transport Layer (Layer 4 in OSI, also a layer in TCP/IP) is primarily responsible for establishing and maintaining end-to-end communication between hosts. It ensures reliable data delivery using connection-oriented protocols like TCP, which provides error checking and flow control.
Question 6: The TCP/IP model's Application layer combines the functions of which three layers of the OSI model?
- Network, Data Link, and Physical
- Session, Presentation, and Application (Correct answer)
- Transport, Network, and Data Link
- Physical, Data Link, and Session
Correct answer: Session, Presentation, and Application
The TCP/IP model is a more condensed framework than the OSI model. Its Application layer encompasses the responsibilities of the OSI model's Application (Layer 7), Presentation (Layer 6), and Session (Layer 5) layers.
CCST - Cisco Certified Support Technician OSI and TCP/IP Models Questions and Answers 1
A network technician is troubleshooting an issue where a user can ping the IP address of a web server but cannot open the website in their browser.
At which layer of the OSI model is the problem MOST likely occurring?