Networking Interview Questions and Answers

1. What do you understand by computer networking?


A computer networking comprises  two or more computers connected through some communication media and network components in order to  share network resources among each other.

The communication media can be wired or wireless. The commonly used wired media are twisted pair cable, coaxial cable and optical fibre.

The wireless media can be radio frequency, infrared or Bluetooth.

The common network devices used in computer networks are hubs, bridges, switches, routers, gateway and NIC.

The network resources can be both hardware and software. The hardware resources can be shared printers, scanners, storage devices etc. The software resources include files, applications and other software.

2. What are the different types of networks?


Computer networks can be classified into different types.

  • PAN (Personal Area Network)
  • LAN (Local Area Network)
  • MAN (Metropolitan Area Network)
  • WAN (Wide Area Network)

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3. What is network topology?


The network topology defines the structural arrangement of these network components how they are interconnected with each other. In other words, the network topology may be defined as the schematic layout of transmission cables connecting various network devices and nodes in a network.

4. What are the different types of network topology?


Different types of topology

  • Bus topology
  • Ring topology
  • Star topology
  • Mesh topology
  • Hybrid topology

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5. What are the different layers of the OSI model?


The OSI Model is divided into 7 distinct layers as follows:

  • Application layer
  • Presentation layer
  • Session layer
  • Transport layer
  • Network layer
  • Data link layer
  • Physical layer

6. What is the function of the application layer?


It is the highest and the seventh layer of the OSI model. It provides the interface between the end-user and the network services like email, sharing data files, web browsing, telnet, DNS, DHCP, etc. The application layer helps the end-user and the software to get access to the network.

Various protocols are used by the Application layer namely, HTTP (HyperText Transfer Protocol), SMTP (Simple Mail Transfer Protocol), IMAP (Internet Message Access Protocol), Telnet, DHCP (Dynamic Host Configuration Protocol), DNS (Domain Name System), FTP ( File Transfer Protocol) and so on.

7. What is the function of the presentation layer?


It is the sixth layer of the OSI model and deals with the syntax and semantics of the information exchanged between the two entities. The major functions of Presentation layer are : translation, encryption/decryption and compression/decompression.

  • Translation: The information exchanges between the devices may be in the form of characters, strings, numbers, and so on. So, they must be translated into a common format, as different computers use their encoding system. Hence, the presentation layer helps to provide interoperability between different encoding systems by translating them into common encoding formats like ASCII or EBCDIC.
  • Encryption/decryption: The information exchanged between the two systems may contain secured or sensitive data. Hence, to maintain the privacy of such sensitive information, encryption is done at the sending end and the decryption is performed at the receiving end so that the process is reversed to get back the information to its original form.
  • Compression/decompression: The information to be carried may be in the form of text, audio, and video files which are of varying large sizes. Therefore, data compression reduces the size of the information and then transmitted it to the receiver. The decompression process is done at the receiving end to recover the compressed information.

8. What is the function of the session layer?


It is the fifth layer of the OSI model. The role of the session layer is to establish, maintain, monitor, and synchronize the dialogue control between the two sessions.

The major functions of the session layer are  :

  • Dialogue control: The session layer allows two systems t initiate communication in half-duplex or full-duplex.
  • Token management: The session layer prevents two systems to perform operations at the same time.
  • Synchronization: Synchronisation takes place between two hosts to recognize each other.

9. What are the different functions of the transport layer?


It is the fourth layer of the OSI model and deals with the process communication between the two systems.

The transport layer receives the data from the upper layer, breaks down them into smaller uniform units called segments, and passes them into the network layer.

The major functions of the Transport layer are :

  • Segmentation and reassembly: Data received from the upper layer is broken down into smaller units of fixed sizes called segments. Each segment is tagged with the sequence numbers so that the transmitted segment can be reassembled correctly at the destination end.
  • Service point addressing: The transport layer deals with the process to process communication between the systems for which it uses the service point address or port address ( port number) to distinguish the specific process.
  • Connection control: The types of connections are used by the transport layer namely: connection-oriented and connectionless.

The connection-oriented transport layer, at first, establishes the connection between the source and destination. Each segment transmitted to the destination is ensured that the segment is received correctly or not. The sender retransmits the same segment again and again until the acknowledgement is received by the sender. It uses the connection-oriented protocol TCP ( Transmission Control Protocol). This protocol is considered to be a reliable protocol. But, it is a slower connection, hence cannot be used in real-time communication.

The connectionless transport layer does not wait for the acknowledgement of the packet received by the destination node. It just assumes that the packet has been reached the destination just fine and keep on sending the consecutive packet without waiting for an acknowledgement. There is no need of establishing a connection between the source and destination. Hence, it is called connectionless. It is also called unreliable because there is no guarantee of the delivery of data packets. However, it provides faster communication between devices other than connection-oriented transmission. Hence, connectionless transmission is used in real-time communication like Live video streaming, video conferencing, etc. UDP (User Datagram Protocol) is the most important connectionless protocol used in the transport layer.

10. What are the main functionalities Network layer?


Another important layer of the OSI model is the network layer which is responsible for the delivery of packets from source to destination across communication networks using multiple links. IP (Internet Protocol) is the key protocol in the network layer that provides a logical addressing scheme for moving data packets from source to destination. Every node in a network is uniquely identified by its respective IP address. Hence, the network layer adds source IP address and destination IP address to the PDU received from the transport layer.

The router is a vital network layer device that acts as a network controller and routes the packet to its desired destination.

11. Explain the functions of the data link layer?


It is layer 2 of the OSI model and is responsible for reliable node-to-node delivery of data packets. The data link layer adds a physical (mac)address to the packet received from the network layer to create frames. Other than adding a mac address in the frame header, the data link layer also adds a frame check sequence to its trailer for error-free delivery of data frames from source to destination.

The data link layer is further subdivided into two distinct sub-layer.

  • LLC (Logical link control ) sublayer
  • MAC (Media Access Control) sublayer

LLC sublayer provides the interface between the multiple network layer protocols like internet protocol and the media access methods using multiplexing techniques. It is responsible for error control and the end to end the flow of frames.

MAC sublayer is responsible for adding the physical address to the data packets from the upper layer to constitute frames. It also provides an interface between the LLC sublayer and the physical layer of the OSI model. It acts as a multiple channel access mechanism for different transmission technologies.

12. What is the function of the data link layer?


It is the lowermost layer or layer 1 of the OSI model and is responsible for the physical connectivity of two different nodes for data communication. It converts digital data into streams of raw bits and transmits them through communication media in the form of electrical or optical signals. different types of encoding techniques are used to transmit these strings of 0’s and 1’s through the transmission channel.

13. How many layers are there in the TCP/ IP model?


The TCP/IP model is divided into four distinct layers to understand the functionalities of different protocols implemented in each layer.

14. Enumerate the major difference between the OSI model and the TCP/IP model?


OSI Model TCP/IP Model
OSI stands for Open System Interconnect TCP/IP stands for Transmission Control Protocol – Internet Protocol.
OSI model consists of 7 different layers. TCP/IP model consists of 4 layers.
Seven different layers are as follows:

  • Application Layer
  • Presentation Layer
  • Session Layer
  • Transport layer
  • Network Layer
  • Data kink layer
  • Physical Layer
Four different layers of TCP/IP model are as follows:

  • Application Layer
  • Transport Layer
  • Internet Layer
  • Network access Layer
Functions of three upper layers are defined separately. All three upper layers of OSI model are combined to form only one layer i.e. application layer.
The functions of data link layer and the physical layer are  defined separately Both the data link layer and the physical layer of  OSI model are  combined to form network access layer
The OSI model  is a conceptual or a referrence model. TCP/IP model is  a practical model and Internet is based on TCP/IP model.
OSI uses vertical approach. TCP/IP uses horizontal approach.

15. What is the network protocol?


In a communication network, when two entities exchange information between them, they must be agreed upon a common set of rules and guidelines. Such a set of rules and regulations which govern data communication between the devices is called network protocol.

Different protocols have their own set of rules and regulations to perform specific processes during the exchange of information between the devices. Such protocols are operated in different layers of network models. Some of the most commonly used protocols are listed below:

  • HTTP (HyperText Transfer Protocol)
  • HTTPS (HyperText Transfer Protocol Secure)
  • SMTP (Simple Mail Transfer Protocol)
  • POP (Post Office Protocol)
  • IMAP (Internet Message Access Protocol)
  • FTP (File Transfer Protocol)
  • Telnet
  • DNS  (Domain Name Service)
  • DHCP (Dynamic Host Configuration Protocol)
  • TCP (Transmission Control Protocol)
  • UDP (User Datagram Protocol)
  • IP (Internet Protocol)
  • ICMP (Internet Control Message  Protocol)
  • ARP (Address Resolution Protocol)
  • RARP (Reverse Address Resolution Protocol)

16. What are the different types of network devices?


The most popularly used network devices are:

  • Repeater
  • Hub
  • Bridge
  • Ethernet Switch
  • Router
  • Gateway
  • Network Interface Card (NIC)

networking interview questions and answers -network devices

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17. Differentiate between hub and switch.


Switch is a layer 2 device. it operates at data link layer of OSI model. Basically it is used at LAN environment. Switch is more intelligent than hub because when a switch receives data frames, it inspects the destination Mac address of the frame. It then checks whether the destination Mac address is mapped with which switch port and then forward frame to that specific port. Switch has a single collision domain and multiple braodcast domain.

On the other hand, hub is a layer 1 device and operates at physical layer of OSI model. Hub cannot analyse the frame it receives . It simply regenerates the incoming signal and braodcast to all other ports. Hub has a single collision domain and a single broadcast domain.

18. Differentiate between switch and router?


Switch works at data link layer of OSI model and uses Mac address to forward frames from one port to another.  It maintains Mac address for mapping Mac address with the switch port.

Router is a layer 3 device and operates at network layer of OSI model. Router makes the decision of packet forwarding using destination  IP address. Router maintains IP routing table. When a router receives the packet and it checks the destination address. It then forwards the packet to the specific destination network  referring to the IP routing table.

19.  What is the difference between intranet and the internet?


Internet Intranet
Interet is global network and provides unlimited connectivity all across the world. Intranet is a network that is within the organization or business and is restricted to access the global network.
Internet is a public network. Intranet is a private network.
Internet can have multiple unlimited connection. Intranet has a limited connection within the network owned by the organization.
Anyone can have access to the internet provided they must have internet connectivity. The access to intranet is allowed only to the authorized users.
Unlimited information available in internet. Limited information available in intranet.

20. What is IP v4 addresses and their different classes?


An Internet Protocol (IP) is a network layer protocol of the OSI model. Its main function is to provide logical addressing for every data packet received from the upper layer. This protocol further adds source IP address and destination IP address to the packet and sent over the network to reach its destination.

Classes of IP address

There are 5 different classes of IP addresses within the available IP range.  The range of the first octet i.e. from 0 to 255 is distributed to classify different classes. Each class has its fixed subnet mask or default subnet mask. The default subnet mask will decide how many hosts can be created in a network.

There are 5 different classes of IP addresses within the available IP range.  The range of the first octet i.e. from 0 to 255 is distributed to classify different classes. Each class has its fixed subnet mask or default subnet mask. The default subnet mask will decide how many hosts can be created in a network.

Classes of IPv4 address IP range Network bits Default subnet mask Application
Class A to 8 Used in larger networks where the number of required hosts per network is more. Example: ISP.
Class B to 16 Used in medium-sized networks such as enterprise networks, medium-sized organizations.
Class C to 24 used by a small network where the number of required hosts per network is limited. Example: private networks like LAN, schools, home, etc.
Class D to Used for multicasting
Class E to Unused, kept reserve for scientific research.

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