CCST - Cisco Certified Support Technician OSI and TCP/IP Models 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?

Accepted Answer

Application Layer

Answer

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?

Accepted Answer

Packet

Answer

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?

Accepted Answer

Internet

Answer

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?

Accepted Answer

Data Link Layer

Answer

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?

Accepted Answer

Establishing reliable, end-to-end connections using protocols like TCP.

Answer

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.

(CCST) Cisco Certified Support Technician Practice Test

(CCST) Cisco Certified Support Technician Practice Test

CCST - Cisco Certified Support Technician OSI and TCP/IP Models Questions and Answers