CCNA- TCP/IP Interview Questions & Answers

What is TCP/IP Model?

TCP/IP is four layer standard model. The four layers of TCP/IP model are

4)Application layer 3)Transport layer 2)Internet layer 1)Network access layer


What are the protocols that are included by each layer of TCP/IP model?

Layers of TCP/IP model                                Protocols
Application DNS, DHCP, FTP, TFTP, SMTP, HTTP, RDP, Telnet, SSH
Transport TCP, UDP
Internet layer IP, ICMP, IGMP
Network access layer Ethernet, Token Ring, FDDI, X.25, Frame Relay, ARP, RARP


What is Encapsulation & De-capsulation?


Encapsulation is the process that occurs when data is to be sent out of the source computer. When data moves from upper layer to lower layer of TCP/IP protocol stack (outgoing transmission), each layer adds the corresponding header to the data.

  • The data package containing the header and the data from the upper layer then becomes the data that is repackaged at the next lower level with lower layer’s header.


De-capsulation, the reverse process of encapsulation occurs when data is received on the destination computer. As the data moves up from the lower layer to the upper layer of TCP/IP protocol stack (incoming transmission), each layer unpacks the corresponding header and uses the information contained in the header to deliver the packet to the exact network application waiting for the data.


What is Message?

The format of the data packet generated at different layers is different, and known by different names.

The data packet created at the Application layer is known as a “MESSAGE”.


What is TCP Segment?

The Application layer message is again encapsulated at the Transport Layer. If the protocol used at the Transport Layer is TCP (Transmission Control Protocol), the data packet is known as a “TCP SEGMENT”.


What is UDP Datagram?

If the protocol used at the Transport layer is UDP (User Datagram Pro to co l), the data packet is known as a “UDP DATAGRAM”.


What is IP Datagram?

The data packet created at the Internet layer by Internet Protocol, which again encapsulates the Transport layer segment/datagram, is known as “IP DATAGRAM”.


What is Frame?

The data packet at the Network Access layer, which encapsulates and may subdivide the IP Datagram, is known as a “FRAME” (generally Ethernet Frame).


What is Error Control & Flow Control?


What is TCP/IP?

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language or protocol of the Internet.
What is Multiplexing and De-multiplexing in TCP/IP?

The data from different applications operating on a network device are multiplexed at the sending device using port numbers and de-multiplexed at the receiving device, again using port numbers.

Multiplexing:- The process of gathering data at the source host from different application processes, enveloping the data with header information to create segments, and passing the segments to the network layer is called multiplexing.

De-multiplexing:- At the receiving end, the transport layer can then examine this field to determine the receiving process, and then direct the segment to that process. This job of delivering the data in a transport-layer segment to the correct application process is called de-multiplexing.



What are IPv4 Address classes?

Class A:- to

Class B:- to

Class C:- to


What is APIPA?

Network is known as APIPA (Automatic Private IPv4 addresses). APIPA range of IPv4 addresses are used when a client is configured to automatically obtain an IPv4 address from the DHCP server was unable to contact the DHCP server for dynamic IPv4 address.


What are Private IPv4 Addresses?

Class A:- to

Class B:- from to

Class C:- to


OSI & TCP/IP Model Comparision



I’ll keep on improvising..


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