Networking Interview Questions and Answers

Networking Interview Questions and Answers

1) What is a Network?

Answer: The network is defined as a set of devices connected to each other through a physical transmission medium.

For example, a computer network is a group of computers connected to each other to communicate and share information and resources such as hardware, data, and software. In a network, nodes are used to connect two or more networks.

2) What is a Node?

Answer: Two or more computers are directly connected by fiber optics or any other cable. A node is a point where a connection is established. It is a network component used to send, receive, and forward electronic information.

A device connected to a network is also called a Node. Let us consider that in a network there are 2 computers, 2 printers, and a server connected, then we can say that there are five nodes in the network.

3) What is Network Topology?

Answer: Network topology is a physical layout of the computer network and defines how computers, devices, cables, etc. are connected to each other.

4) What are Routers?

Answer: A router is a network device that connects two or more network segments. It is used to transfer information from source to destination.

Routers send the information in terms of data packets and when these data packets are forwarded from one router to another router, the router reads the network address in the packets and identifies the destination network.

5) What is the OSI reference model?

Answer: Open Systems Interconnection, the name itself suggests that it is a reference model that defines how applications can communicate with each other through a network system.

It also helps to understand the relationship between networks and defines the communication process in a network.

6) What are the layers in OSI Reference Models? Describe each layer briefly.

Answer: Following are the seven layers of the OSI reference models:

i) Physical Layer (Layer 1): Converts data bits into electrical impulses or radio signals. Example: Ethernet.

ii) Data Link Layer (Layer 2): In the data link layer, data packets are encoded and decoded into bits and provide node-to-node data transfer. This layer also detects errors that occurred at Layer 1.

iii) Network Layer (Layer 3): This layer transfers data sequences of variable length from one node to another node in the same network. This variable-length data stream is also known as "Datagrams".

iv) Transport Layer (Layer 4): Transfers data between nodes and also provides acknowledgment of successful data transmission. It keeps track of the transmission and sends the segments again if the transmission fails.

(OSI Reference Model)

v) Session layer (Layer 5): This layer manages and controls the connections between computers. It establishes, coordinates, exchanges, and terminates connections between local and remote applications.

vi) Presentation Layer (Layer 6): It is also known as the "Syntax Layer". Layer 6 transforms the data into the format that the application layer accepts.

vii) Application Layer (Layer 7): This is the last layer of the OSI Reference Model and is the one closest to the end-user. Both the end-user layer and the application layer interact with the software application. This layer provides email services, file transfer, etc.

7) What is the difference between Hub, Switch, and Router?

Answer:

Hub	Switch	Router
Hub is the least expensive, least intelligent, and least complicated of the three. It broadcast all data to every port which may cause serious security and reliability concerns	Switches work similarly to Hubs but in a more efficient manner. It creates connections dynamically and provides information only to the requesting port	The router is the smartest and most complicated out of these three. It comes in all shapes and sizes. Routers are similar to little computers dedicated to routing network traffic
In a Network, Hub is a common connection point for devices connected to the network. Hub contains multiple ports and is used to connect segments of LAN	A switch is a device in a network that forwards packets in a network	Routers are located at the gateway and forwards data packets

8) Explain TCP/IP Model

Answer: The most widely used and available protocol is TCP/IP, that is, the Transmission Control Protocol and the Internet Protocol. TCP/IP specifies how data should be packaged, transmitted, and routed in its end-to-end data communication.

There are four layers as shown in the below diagram:

(TCP/IP MODEL)

Given below is a brief explanation of each layer:

• Application Layer: This is the top layer in the TCP/IP model. It includes processes that use the Transport Layer Protocol to transmit the data to their destination. There are different Application Layer Protocols such as HTTP, FTP, SMTP, SNMP protocols, etc.
• Transport Layer: It receives the data from the Application Layer which is above the Transport Layer. It acts as a backbone between the host’s systems connected with each other and it is mainly concerned with the transmission of data. TCP and UDP are mainly used as Transport Layer protocols.
• Network or Internet Layer: This layer sends the packets across the network. Packets mainly contain source & destination IP addresses and actual data to be transmitted.
• Network Interface Layer: It is the lowest layer of the TCP/IP model. It transfers the packets between different hosts. It includes encapsulation of IP packets into frames, mapping IP addresses to physical hardware devices, etc.

9) What is HTTP and what port does it use?

Answer: HTTP is the Hypertext Transfer Protocol and is responsible for web content. Many web pages use HTTP to transmit web content and enable hypertext display and navigation. It is the main protocol and the port used here is TCP port 80.

10) What is HTTPS and what port does it use?

Answer: HTTPS is secure HTTP. HTTPS is used for secure communication over a computer network. HTTPS provides website authentication that prevents unwanted attacks.

In bidirectional communication, the HTTPS protocol encrypts the communication to prevent data manipulation. With the help of an SSL certificate, it verifies whether the requested server connection is a valid connection or not. HTTPS uses TCP with port 443.

11) What are TCP and UDP?

Answer: Common factors in TCP and UDP are:

• TCP and UDP are the most widely used protocols that are built on the top of the IP protocol.
• Both protocols TCP and UDP are used to send bits of data over the Internet, which is also known as ‘packets’.
• When packets are transferred using either TCP or UDP, it is sent to an IP address. These packets are traversed through routers to the destination.

The difference between TCP and UDP are enlisted in the below table:

TCP	UDP
TCP stands for Transmission Control	UDP stands for User Datagram Protocol or Universal Datagram Protocol
Once the connection is set up, data can be sent bi-directional i.e. TCP is a connection-oriented protocol	UDP is a connectionless, simple protocol. Using UDP, messages are sent as packets
The speed of TCP is slower than UDP	UDP is faster compared to TCP
TCP is used for the application where time is not a critical part of data transmission	UDP is suitable for applications that require the fast transmission of data and time is crucial in this case.
TCP transmission occurs in a sequential manner	UDP transmission also occurs in a sequential manner but it does not maintain the same sequence when it reaches the destination
It is the heavyweight connection	It is the lightweight transport layer
TCP tracks the data sent to ensure no data loss during data transmission	UDP does not ensure whether the receiver receives packets are not. If packets are misses then they are just lost

12) What is a Firewall?

Answer: Firewall is a network security system used to protect computer networks from unauthorized access. It prevents malicious access from the outside to the computer network. A firewall can also be built to grant limited access to external users.

The firewall consists of a hardware device, a software program, or a combination of both. All messages that are routed through the firewall are examined against specific security criteria, and messages that meet the criteria are successfully traversed through the network or otherwise blocked.

Firewalls can be installed like any other computer software and can then be customized as needed and have some control over access and security features.

“Windows Firewall” is a built-in Microsoft Windows application that comes with the operating system. This “Windows Firewall” also helps prevent viruses, worms, etc.

13) What is DNS?

Answer: Domain Name Server (DNS), in non-professional language and we can call it Internet phone book. All public IP addresses and their hostnames are stored in the DNS and then translated into a corresponding IP address.

For a human being, it is easy to remember and recognize the domain name, however, the computer is a machine that does not understand human language and only understands the language of IP addresses for data transfer.

There is a "Central Registry" where all domain names are stored and updated regularly. All Internet Service Providers and different hosting companies usually interact with this central registry to get up-to-date DNS details.

14) What is the difference between a Domain and a Workgroup?

Answer: In a computer network, the different computers are organized in different methods and these methods are: Domains and Workgroups. Typically, computers running on the home network belong to a workgroup.

However, computers running on an office network or any working network belong to the Domain.

Their differences are as follows:

Workgroup	Domain
All computers are peers and no computer has control over another computer	Network admin uses one or more computers as a server and provides all-access, and security permission to all other computers in a network
In a Workgroup, each computer maintains their own database	The domain is a form of a computer network in which computers, printers, and user accounts are registered in a central database.
Each computer has its own authentication rule for every user account	It has centralized authentication servers which set the rule of authentication
Each computer has a set of user accounts. If the user has an account on that computer then only the user able to access the computer	If the user has an account in a domain then the user can log in to any computer in a domain
Workgroup does not bind to any security permission or does not require any password	Domain user has to provide security credentials whenever they are accessing the domain network
Computer settings need to change manually for each computer in a Workgroup	In a domain, changes made in one computer automatically made the same changes to all other computers in a network
All computers must be on the same local area network	In a domain, computers can be on a different local network
In a Workgroup, there can be only 20 computers connected	In a domain, thousands of computers can be connected

15) What is a Proxy Server and how do they protect the computer network?

Answer: For data transmission, IP addresses are required and even DNS uses IP addresses to route to the correct website. It means that without the knowledge of the correct and real IP addresses it is not possible to identify the physical location of the network.

Proxy servers prevent unauthorized external users from accessing those IP addresses on the internal network. It makes the computer network virtually invisible to outside users.

Proxy Server also maintains the list of blacklisted websites so that the internal user is not easily infected with viruses, worms, etc.

16) What are IP classes and how can you identify the IP class of a given IP address?

Answer: An IP address has 4 sets (octets) of numbers, each with a value of up to 255.

For example, home or business connection range started mostly between 190x or 10x. IP classes differ based on the number of hosts they support on a single network. If the IP classes support more networks, there are very few IP addresses available for each network.

There are three types of IP classes and they are based on the first octet of IP addresses being classified as Class A, B, or C. If the first octet starts with 0 bits then it is of type Class A.

The Class A type has a range of up to 127.x.x.x (except 127.0.0.1). If it starts with bits 10, then it belongs to Class B. Class B has a range of 128.x to 191.x. IP class belongs to Class C if the octet starts with bits 110. Class C has a range from 192.x to 223.x.

17) What is meant by 127.0.0.1 and localhost?

Answer: The IP address 127.0.0.1 is reserved for loopback or localhost connections. These networks are usually reserved for the largest customers or some of the original members of the Internet. To identify any connection issues, the initial step is to ping the server and see if it responds.

If there is no response from the server, there are several causes, such as the network is down, the cable needs to be replaced, or the network card is not in good condition. 127.0.0.1 is a loopback connection on the network interface card (NIC) and if you can successfully ping this server, the hardware is good.

127.0.0.1 and localhost are the same in most computer network operations.

18) What is the NIC?

Answer: NIC stands for Network Interface Card. Also known as a network adapter or Ethernet card. It is in the form of an add-in card and is installed on a computer so that the computer can connect to a network.

Each NIC has a MAC address that helps identify the computer on a network.

19) What is data encapsulation?

Answer: In a computer network, to allow data to be transmitted from one computer to another, network devices send messages in the form of packets. The OSI reference model layer then aggregates these packets with the IP header.

The data link layer encapsulates each packet in a frame that contains the hardware address of the source and destination computer. If a destination computer is on the remote network, frames are routed through a gateway or router to the destination computer.

20) What is the difference between the Internet, Intranet, and Extranet?

Answer: The terminologies Internet, Intranet, and Extranet are used to define how applications can be accessed on the network. They use similar TCP/IP technology but differ in terms of access levels for each user inside and outside the network.

• Internet: Applications can be accessed by anyone from anywhere via the web.
• Intranet: This allows limited access to users from the same organization.
• Extranet: External users are allowed or provided access to use the organization's network application.

21) What is a VPN?

Answer: VPN is the virtual private network and it is based on the Internet as a private wide area network. Internet-based VPNs are less expensive and can be connected from anywhere in the world.

VPNs are used to connect offices remotely and are less expensive compared to WAN connections. VPNs are used for secure transactions and sensitive data can be transferred between multiple offices. VPN keeps company information safe from any possible intrusion.

22) What are Ipconfig and Ifconfig?

Answer: Ipconfig stands for Internet Protocol Configuration and this command is used in Microsoft Windows to view and configure the network interface.

The Ipconfig command is useful for displaying all TCP/IP network summary information currently available on a network. It also helps to modify DHCP protocol and DNS settings.

Ifconfig (Interface Configuration) is a command used on Linux, Mac, and UNIX operating systems. It is used to configure and control the parameters of the TCP/IP network interface from the CLI, that is, the command-line interface. Allows you to view the IP addresses of these network interfaces.

23) Explain DHCP briefly?

Answer: DHCP stands for Dynamic Host Configuration Protocol and automatically assigns IP addresses to network devices. It completely eliminates the process of manually assigning IP addresses and reduces the errors caused by this.

This entire process is centralized so that TCP/IP configuration can also be completed from a central location. DHCP has an "IP address pool" from which it assigns an IP address to network devices. DHCP cannot recognize if any device is manually configured and assigned with the same IP address from the DHCP pool.

24) What are the different types of a network? Explain each briefly.

Answer: There are 4 main types of networks.

Let's take a look at each of them in detail.

1. Personal Area Network (PAN): This is the smallest and most basic type of network often used in the home. It is a connection between the computer and another device such as a phone, printer, modem, tablet, etc.
2. Local Area Network (LAN): LAN is used in small offices and internet cafes to connect a small group of computers together. They are usually used to transfer a file or to play games over a network.
3. Metropolitan Area Network (MAN): It is a more powerful type of network than LAN. The area covered by MAN is a small town, city, etc. A huge server is used to cover such a large area for connection.
4. Wide Area Network (WAN): It is more complex than the LAN and covers a large area, usually a large physical distance. The Internet is the largest WAN that spans the entire world. WAN is not owned by a single organization but has distributed ownership.

There are some other types of the network as well:

• Storage Area Network (SAN)
• System Area Network (SAN)
• Enterprise Private Network (EPN)
• Passive Optical Local Area Network (POLAN)

25) Differentiate Communication and Transmission?

Answer: Through streaming, data is transferred from the source to the destination (only one way). It is treated as the physical movement of data.

Communication means the process of sending and receiving data between two media (data is transferred between source and destination in both directions).

26) Describe the layers of the OSI model?

Answer: The OSI model stands for Open System Interconnection. It is a framework that guides applications on how they can communicate on a network.

The OSI model has seven layers. They are listed below,

1. Physical Layer: Deals with the transmission and reception of unstructured data through a physical medium.
2. Data Link Layer: Helps to transfer error-free data frames between nodes.
3. Network layer: decides the physical path that data should take based on network conditions.
4. Transport layer: ensures that messages are delivered in sequence and without loss or duplication.
5. Session layer: helps to establish a session between processes of different stations.
6. Presentation Layer: Formats the data as needed and presents it to the application layer.
7. Application Layer: Serves as a mediator between users and application processes.

27) Explain various types of networks based on their sizes?

Answer: The size of the network is defined as the geographical area and the number of computers it covers. Depending on the size of the network, they are classified as follows:

• Local Area Network (LAN): A network with a minimum of two computers up to a maximum of thousands of computers within an office or building is called a LAN. Generally, it works for a single site where people can share resources like printers, data storage, etc.
• Metropolitan Area Network (MAN): It is larger than LAN and is used to connect multiple LANs in small regions, a city, colleges, university campuses, etc., which in turn forms a larger network.
• Wide Area Network (WAN): Multiple LANs and MANs connected together form a WAN. It covers a wider area like a whole country or the world.

28) Expand SLIP?

Answer: SLIP stands for Serial Line Interface Protocol. SLIP is a protocol used for transmitting IP datagrams over a serial line.

29) What is an Encoder?

Answer: An encoder is a circuit that uses an algorithm to convert any data or compress audio data or video data for transmission purposes. An encoder converts the analog signal into a digital signal.

30) What is a Decoder?

Answer: A decoder is a circuit that converts the encoded data to its actual format. It converts the digital signal into an analog signal.

31) Brief Ethernet?

Answer: Ethernet is a technology that is used to connect computers all over the network to transmit the data between each other.

32) What is the use of encryption and decryption?

Answer: Encryption is the process of converting the transmission data into another form that is not read by any other device other than the intended receiver.

Decryption is the process of converting back the encrypted data to its normal form. An algorithm called cipher is used in this conversion process.

33) Define IEEE in the networking world?

Answer: IEEE stands for the Institute of Electrical and Electronics Engineers. This is used to design or develop standards that are used for networking.

34) Define Static IP and Dynamic IP?

Answer: When a device or computer is assigned a specified IP address then it is named Static IP. It is assigned by the Internet Service Provider as a permanent address.

Dynamic IP is the temporary IP address assigned by the network to a computing device. Dynamic IP is automatically assigned by the server to the network device.

35) What is the full form of ASCII?

Answer: ASCII stands for American Standard Code for Information Interchange.

36) What is the full form of IDEA?

Answer: IDEA stands for International Data Encryption Algorithm.

37) In how many ways the data is represented and what are they?

Answer: Data transmitted through the networks comes in different ways like text, audio, video, images, numbers, etc.

• Audio: It is nothing but the continuous sound which is different from text and numbers.
• Video: Continuous visual images or a combination of images.
• Images: Every image is divided into pixels. And the pixels are represented using bits. Pixels may vary in size based on image resolution.
• Numbers: These are converted into binary numbers and are represented using bits.
• Text: Text is also represented as bits.

38) Define various types of Internet connections?

Answer: There are three types of Internet connections. They are listed below:

• Broadband Connection: This type of connection gives continuous high-speed Internet. In this type, if we log off from the Internet for any reason then there is no need to log in again. For Example, Modems of cables, Fibres, wireless connections, satellite connections, etc.
• Wi-Fi: It is a wireless Internet connection between the devices. It uses radio waves to connect to devices or gadgets.
• WiMAX: It is the most advanced type of Internet connection which is more featured than Wi-Fi. It is nothing but a high-speed and advanced type of broadband connection.

39) Explain the characteristics of networking?

Answer: The main characteristics of networking are mentioned below:

• Topology: This deals with how the computers or nodes are arranged in the network. The computers are arranged physically or logically.
• Protocols: Deals with the process of how computers communicate with one another.
• Medium: This is nothing but the medium used by computers for communication.

40) How many types of modes are used in data transferring through networks?

Answer: Data transferring modes in computer networks are of three types. They are listed below,

• Simplex: Data transferring that takes place only in one direction is called Simplex. In Simplex mode, the data gets transferred either from sender to receiver or from receiver to sender. For Example, Radio signal, the print signal given from computer to printer, etc.
• Half Duplex: Data transferring can happen in both directions but not at the same time. Alternatively, the data is sent and received. For Example, Browsing through the internet, a user sends the request to the server and later the server processes the request and sends back the web page.
• Full Duplex: Data transferring happens in both directions that too simultaneously. For Example, Two-lane roads where traffic flows in both directions, communication through telephone, etc.

41) What is a subnet?

Answer: A subnet is a network within a network achieved by the process called subnetting which helps to divide a network into subnets. It is used for greater routing efficiency and improves network security. Reduces the time to extract the host address from the routing table.