CCNA Exam – OSI & TCP/IP Model

Question 1

Where does routing occur within the DoD TCP/IP reference model?

A. application
B. internet
C. network
D. transport


Answer: B


The picture below shows the comparison between TCP/IP model & OSI model. Notice that the Internet Layer of TCP/IP is equivalent to the Network Layer which is responsible for routing decision.



Question 2

Refer to exhibit.



A network administrator cannot establish a Telnet session with the indicated router. What is the cause of this failure?

A. A Level 5 password is not set.
B. An ACL is blocking Telnet access.
C. The vty password is missing.
D. The console password is missing.


Answer: C


Question: 3

Before installing a new, upgraded version of the IOS, what should be checked on the router, and which command should be used to gather this information? (Choose two)

A. the amount of available ROM
B. the amount of available flash and RAM memory
C. the version of the bootstrap software present on the router
D. show version
E. show processes
F. show running-config


Answer: B D


When upgrading new version of the IOS we need to copy the IOS to the Flash so first we have to check if the Flash has enough memory or not. Also running the new IOS may require more RAM than the older one so we should check the available RAM too. We can check both with the “show version” command.


Question 4

Refer to the exhibit. An administrator pings the default gateway at and sees the output as shown. At which OSI layer is the problem?








A. data link layer
B. application layer
C. access layer
D. session layer
E. network layer


Answer: E


The Network layer is responsible for network addressing and routing through the internetwork. So a ping fails, you may have an issue with the Network layer (although lower layers like Data Link & Physical may cause the problem).

Question 5

At which layer of the OSI model does PPP perform?

A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 5


Answer: A


Question 6

A network administrator is verifying the configuration of a newly installed host by establishing an FTP connection to a remote server. What is the highest layer of the protocol stack that the network administrator is using for this operation?

A. application
B. presentation
C. session
D. transport
E. internet
F. data link


Answer: A


FTP belongs to Application layer and it is also the highest layer of the OSI model.

Question 7

At which layer of the OSI model is RSTP used to prevent loops?

A. data link
B. network
C. physical
D. transport


Answer: A

Question 8

Which layer in the OSI reference model is responsible for determining the availability of the receiving program and checking to see if enough resources exist for that communication?

A. transport
B. network
C. presentation
D. session
E. application


Answer: E

Question 9

A receiving host computes the checksum on a frame and determines that the frame is damaged. The frame is then discarded. At which OSI layer did this happen?

A. session
B. network
C. physical
D. data link
E. transport


Answer: D


When using the term “frame” we can easily recognize it belongs to the Data Link layer. In this layer, an Frame Check Sequence (FCS) field is added to the frame to verify that the frame data is received correctly.

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