Networking Interview Questions and Answers
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Introduced in the late 1950s for the purpose to serve the U.S. military radar system, commonly known as SAGE (Semi-Automatic Ground Environment), computer networking is the field that has great opportunities for the candidates who are willing to pursue it as a career option. The primary objective of introducing networking is to enable the nodes to share relevant resources across different platforms.
In the field of computer networks, exchanging data through computing devices are performed using data links or connections between nodes. These connections or the data links are fixed over cable media which includes wires, optic cables, wireless media like Wi-Fi. With the increasing demand in the market, networking over a period of time, have gained a lot of momentum and is a must-required resource in the market.
Best Networking Interview Questions of 2020
Q1) What is a Network?
Ans: A network is a set of devices connected to each other using a physical transmission medium.
Example: A Computer Network is a group of computers connected with each other to communicate and share information and resources like hardware, data, and software across each other.
In a network, nodes are used to connect two or more networks.
Q2) What is a Node?
Ans: Two or more computers are connected directly by an optical fiber or any other cable. A node is a point where a connection established. It is a network component which is used to send, receive and forward the electronic information.
A device connected to a network is also termed as Node. Let's consider that in a network there are 2 computers, 2 printers, and a server are connected, then we can say that there are five nodes on the network.
image source: Nodes
Q3)What is Network Topology?
Ans:Network Topology is a physical layout of the computer network and it defines how the computers, devices, cables etc are connected to each other.
Q4) What are Routers?
Ans: The router is a network device which connects two or more network segments. The router is used to transfer information from the 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 then the router reads the network address in the packets and identifies the destination network.
Q5) What is OSI reference model?
Ans: Open System Interconnection, the name itself suggest that it is a reference model which defines how applications can communicate with each other over a networking system.
It also helps to understand the relationship between networks and defines the process of communication in a network.
Q6) What are the layers in OSI Reference Models? Describe each layer briefly.
Ans: Given below are the seven layers of OSI Reference Models:
#1) Physical Layer (Layer 1): Physical Layer converts data bits into electrical impulse or radio signals. E.g. Ethernet.
#2) Data Link Layer (Layer 2): At Data Link layer, data packets are encoded and decoded into bits and it provides a node to node data transfer. Data Link Layer also detects the errors occurred at Layer 1.
#3) Network Layer (Layer 3): Network Layer transfers variable length data sequence from one node to another node in the same network. This variable length data sequence is also known as “Datagrams”.
#4) Transport Layer (Layer 4): It transfers data between nodes and also provides acknowledgment of successful data transmission. It keeps track of transmission and sends the segments again if the transmission fails.
#5) Session Layer (Layer 5): Session Layer manages and controls the connections between computers. It establishes, coordinates, exchange and terminates the connections between local and the remote applications.
#6) Presentation Layer (Layer 6): It is also called as “Syntax Layer”. Layer 6 transforms the data into the form in which the application layer accepts.
#7) Application Layer (Layer 7): This is the last layer of OSI Reference Model and is the one which is close to the end user. Both end-user and application layer interacts with the software application. This layer provides services for email, file transfer etc.
Q7) What is the difference between Hub, Switch, and Router?
Hub is least expensive, least intelligent and least complicated of the three.
It broadcast all data to every port which may cause serious security and reliability concern
Switches work similarly like Hubs but in a more efficient manner.
It creates connections dynamically and provides information only to the requesting port
The router is smartest and most complicated out of these three. It comes in all shapes and sizes. Routers are similar like little computers dedicated for 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
Switch is a device in a network which forwards packets in a network
Routers are located at gateway and forwards data packets
Q8)Explain TCP/IP Model
Ans: The most widely used and available protocol is TCP/IP i.e. Transmission Control Protocol and Internet Protocol. TCP/IP specifies how data should be packaged, transmitted and routed in their end to end data communication.
There are four layers as shown in the below diagram:
image source: TCP/IP
Given below is a brief explanation of each layer:
Application Layer: This is the top layer in TCP/IP model. It includes processes which use 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 Transport Layer. It acts as a backbone between the host's system connected with each other and it mainly concerns about the transmission of data. TCP and UDP are mainly used as a 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 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.
Q9) What is HTTP and what port does it use?
Ans: HTTP is HyperText Transfer Protocol and it is responsible for web content. Many web pages are using HTTP to transmit the web content and allow the display and navigation of HyperText.
It is the primary protocol and port used here is TCP port 80.
Q10) What is HTTPs and what port does it use?.
Ans: HTTPS is a Secure HTTP. HTTPS is used for secure communication over a computer network. HTTPS provides authentication of websites which prevents unwanted attacks.
In a bi-directional communication, HTTPS protocol encrypts the communication so that tampering of the data gets avoided. With the help of a SSL certificate, it verifies if the requested server connection is a valid connection or not. HTTPS uses TCP with port 443.
Q11) What are TCP and UDP?
Ans: Common factors in TCP and UDP:
- TCP and UDP are the most widely used protocols that are built on the top of 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.
TCP stands for Transmission Control Protocol
UDP is stands for User Datagram Protocol or Universal Datagram Protocol
Once the connection is setup, data can be sent bi-directional i.e. TCP is a connection oriented protocol
UDP is 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 critical part of data transmission
UDP is suitable for the applications which require 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 heavy weight connection
It is lightweight transport layer
TCP tracks the data sent to ensure no data loss during data transmission
UDP does not ensure whether receiver receives packets are not. If packets are misses then they are just lost
- 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.
Q12) What is a Firewall?
Ans: Firewall is a network security system that is used to protect computer networks from unauthorized access. It prevents malicious access from outside to the computer network. A firewall can also be built to grant limited access to the outside users.
The firewall consists of a hardware device, software program or a combined configuration of both. All the messages that route through the Firewall are examined by specific security criteria and the messages which meet the criteria are successfully traversed through the network or else those messages are blocked.
image source: Firewall
Firewalls can be installed just like any other computer software and later can be customized as per the need and have some control over the access and security features. “
Windows Firewall” is an inbuilt Microsoft Windows application which comes along with the operating system. This “Windows Firewall” also helps to prevent viruses, worms etc.
Q13) What is DNS?
Ans: Domain Name Server (DNS), in a non-professional language and we can call it as Internet’s phone book. All the public IP addresses and their hostnames are stored in the DNS and later it translates 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 the human language and they only understand the language of IP addresses for data transfer.
There is a “Central Registry” where all the domain names are stored and it gets updated on a periodic basis. All the internet service providers and different host companies usually interact with this central registry to get the updated DNS details.
For Example: When you type a website www.softwaretestinghelp.com, then your internet service provider looks for the DNS associated with this domain name and translates this website command into a machine language – IP address – 188.8.131.52 (note that, this is imaginary IP address and not the actual IP for the given website) so that you will get redirected to the appropriate destination.
This is shortly explained in the below diagram:
image source: DNS
Q14) What is the difference between a Domain and a Workgroup?
Ans: In a Computer Network, different computers are organized in different methods and these methods are – Domains and Workgroups. Usually, computers which run on the home network belong to a Workgroup.
However, computers which are running on an office network or any workplace network belong to the Domain.
All computers are peers and no computer has control over another computer
Network admin uses one or more computer as a server and provide all accesses, 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 their own authentication rule for every user account
It has centralized authentication servers which set the rule of authentication
Each computer has set of user account. If user has account on that computer then only user able to access the computer
If user has an account in a domain then user can login 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 same changes to all other computers in a network
All computers must be on 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
Q15) What is a Proxy Server and how do they protect the computer network?
Ans:For data transmission, IP addresses are required and even DNS uses IP addresses to route to the correct website. It means without the knowledge of correct and actual IP addresses it is not possible to identify the physical location of the network.
Proxy Servers prevent external users who are unauthorized to access such IP addresses of the internal network. The Proxy Server makes the computer network virtually invisible to the external users.
image source: Proxy Server
Q16) What are IP classes and how can you identify the IP class of given a IP address?
Ans: An IP address has 4 sets (octets) of numbers each with a value up to 255.
For Example, the range of the home or commercial connection started primarily between 190 x or 10 x. IP classes are differentiated based on the number of hosts it supports on a single network. If IP classes support more networks then very few IP addresses are available for each network.
There are three types of IP classes and are based on the first octet of IP addresses which are classified as Class A, B or C. If the first octet begins with 0 bit then it is of type Class A.
Class A type has a range 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 having a range from 128.x to 191.x. IP class belongs to Class C if octet starts with bits 110. Class C has a range from 192.x to 223.x.
Q17) What is meant by 127.0.0.1 and local host?
Ans:IP address 127.0.0.1, is reserved for loopback or local host connections. These networks are usually reserved for the biggest customers or some of the original members of the Internet. To identify any connection issue, the initial step is to ping the server and check if it is responding.
If there is no response from the server then there are various causes like the network is down or the cable needs to be replaced or network card is not in a good condition. 127.0.0.1 is a loopback connection on the Network Interface Card (NIC) and if you are able to ping this server successfully, then it means that the hardware is in a good shape and condition.
127.0.0.1 and local host are the same things in most of the computer network functioning.
Q18) What is NIC?
Ans:NIC stands for Network Interface Card. It is also known as Network Adapter or Ethernet Card. It is in the form of add-in card and is installed in a computer so that the computer can be connected to a network.
Each NIC has a MAC address which helps in identifying the computer on a network.
Q19) What is Data Encapsulation?
Ans:In a computer network, to enable data transmission from one computer to another, the network devices send messages in the form of packets. These packets are then added with the IP header by OSI reference model layer.
The Data Link Layer encapsulates each packet in a frame which contains the hardware address of the source and the destination computer. If a destination computer is on the remote network then the frames are routed through a gateway or router to the destination computer.
Q20) What is the difference between Internet, Intranet, and Extranet?
Ans:The terminologies Internet, Intranet, and Extranet are used to define how the applications in the network can be accessed. They use similar TCP/IP technology but differ in terms of access levels for each user inside the network and outside the network.
Internet: Applications are accessed by anyone from any location using the web.
Intranet: It allows limited access to the users in the same organization.
Extranet: External users are allowed or provided with access to use the network application of the organization.
Q21) what is a VPN?
Ans:VPN is the Virtual Private Network and is built 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 when compared to WAN connections. VPNs are used for secure transactions and confidential data can be transferred between multiple offices. VPN keeps company information secure against any potential intrusion.
image source: VPN
Given below are the 3 types of VPN's:
#1) Access VPN: Access VPN's provides connectivity to the mobile users and telecommuters. It is an alternative option for dial-up connections or ISDN connections. It provides low-cost solutions and a wide range of connectivity.
#2) Intranet VPN: They are useful for connecting remote offices using shared infrastructure with the same policy as a private network.
#3) Extranet VPN: Using shared infrastructure over an intranet, suppliers, customers, and partners are connected using dedicated connections.
Q22) what are ipconfig and ifconfig?
Ans:Ipconfig stands for Internet Protocol Configuration and this command is used on Microsoft Windows to view and configure the network interface.
The command ipconfig is useful for displaying all TCP/IP network summary information currently available on a network. It also helps to modify the DHCP protocol and DNS setting.
Ifconfig (Interface Configuration) is a command that is used on Linux, Mac, and UNIX operating system. It is used to configure, control the TCP/IP network interface parameters from CLI i.e. Command Line Interface. It allows you to see the IP addresses of these network interfaces.
Q23) Explain DHCP briefly?
Ans: DHCP stands for Dynamic Host Configuration Protocol and it automatically assigns IP addresses to the network devices. It completely removes the process of manual allocation of IP addresses and reduces the errors caused due to this.
This entire process is centralized so that TCP/IP configuration can also be completed from a central location. DHCP has “pool of IP addresses” from which it allocates the IP address to the network devices. DHCP cannot recognize if any device is configured manually and assigned with the same IP address from the DHCP pool.
In this situation, it throws “IP address conflict” error.
image source: DHCP
DHCP environment requires DHCP servers to set-up the TCP/IP configuration. These servers then assign, release and renew the IP addresses as there might be a chance that network devices can leave the network and some of them can join back to the network.
Q24) What is SNMP?
Ans: SNMP stands for Simple Network Management Protocol. It is a network protocol used for collecting organizing and exchanging information between network devices. SNMP is widely used in network management for configuring network devices like switches, hubs, routers, printers, servers.
SNMP consists of the below components:
- SNMP Manager
- Managed device
- SNMP Agent
- Management Information Base (MIB)
The below diagram shows how these components are connected with each other in the SNMP architecture:
image source: SNMP
SNMP is a part of TCP/IP suite. There are 3 main versions of SNMP which include SNMPv1, SNMPv2, and SNMPv3.
Q25) What are the different types of a network? Explain each briefly.
Ans: There are 4 major types of network.
Let's take a look at each of them in detail.
- Personal Area Network (PAN): It is a smallest and basic network type that is often used at home. It is a connection between the computer and another device such as phone, printer, modem tablets etc
- Local Area Network (LAN): LAN is used in small offices and internet cafe to connect a small group of computers to each other. Usually, they are used to transfer a file or for playing the game in a network.
- Metropolitan Area Network (MAN): It is a powerful network type than LAN. The area covered by MAN is a small town, city etc. A huge server is used to cover such a large span of area for connection.
- Wide Area Network (WAN): It is more complex than LAN and covers a large span of area typically a large physical distance. The Internet is the largest WAN which is spread across the world. WAN is not owned by any single organization but it has distributed ownership.
There are some other types of network as well:
- Storage Area Network (SAN)
- System Area Network (SAN)
- Enterprise Private Network (EPN)
- Passive Optical Local Area Network (POLAN)
Q26) Differentiate Communication and Transmission?
Ans: hrough Transmission the data gets transferred from source to 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 ways).
Q27) Describe the layers of OSI model?
Ans: OSI model stands for Open System Interconnection It is a framework which guides the applications how they can communicate in a network.
OSI model has seven layers. They are listed below,
Physical Layer (Deals with transmission and reception of unstructured data through a physical medium)
Data Link Layer (Helps in transferring error-free data frames between nodes)
Network Layer (Decides the physical path that should be taken by the data as per the network conditions)
Transport Layer (Ensures that the messages are delivered in sequence and without any loss or duplication)
Session Layer (Helps in establishing a session between processes of different stations)
Presentation Layer (Formats the data as per the need and presents the same to Application layer)
Application Layer (Serves as the mediator between Users and processes of applications).
Q28) Explain various types of networks based on their sizes?
Ans: ize of the Network is defined as the geographic area and the number of computers covered in it. Based on the size of the network they are classified as below,
Based on the size of the Network they are classified as below,
Local Area Network (LAN): A network with a minimum of two computers to a maximum of thousands of computers within an office or a building is termed as 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 used to connect various LAN’s across small regions, a city, campus of colleges or universities etc which in turn forms a bigger network.
- Wide Area Network (WAN): Multiple LAN’s and MAN’s connected together form a WAN. It covers a wider area like a whole country or world.
Q29) Define various types of internet connections?
Ans: There are three types of internet connections. They are listed below
1) 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.
Eg: Modems of cables, Fibres, wireless connection, satellite connection etc.
2) Wi-Fi – It is a wireless internet connection between the devices. It uses radio waves to connect to the devices or gadgets.
3) WiMAX – It is the most advanced type of internet connection which is more featured than Wi-Fi. It is nothing but the high-speed and advanced type of broadband connection.
Q30) Few important terminology we come across networking concepts?
Ans: Below are few important terms we need to know in networking
Network – A set of computers or devices connected together with a communication path to share data.
- Networking – The design and construction of a network are termed as networking.
- Link – The physical medium or the communication path through which the devices are connected in a network is called as a Link.
- Node – The devices or the computers connected to the links are named as nodes.
- Router / Gateway – A device/computer/node that is connected to different networks is termed as a Gateway or Router. The basic difference between these two is that Gateway is used to control the traffic of two contradictory networks whereas router controls the traffic of similar networks.
- The router is nothing but a switch which processes the signal/traffic using routing protocols.
- Protocol – A set of instructions or rules or guidelines that are used in establishing communications between computers of a network is called as Protocol.
- Unicasting – When a piece of information or a packet is sent from a particular source to a specified destination then it is called as Unicasting.
- Anycasting – Sending the datagrams from a source to the nearest device among the group of servers which provide the same service as the source is termed as Anycasting.
- Multicasting – Sending one copy of data from a single sender to multiple clients or receivers (selected clients) of the networks which are in need of such data.
- Broadcasting – Sending a packet to each device of the network is termed as broadcasting.
Career scopes and salary scale
Network engineers are known to build and design effective computer networking systems and alternatives. They are also responsible to install software applications that usually make the connections between the organizational services with the client machines at a faster rate. In the world of digitalization, the scope of job opportunities in the field of networking has increased in recent years. Jobs such as network engineering posts is something that you should be looking into.
A fresher in the field of networking is offered about 35,000 to 45,000 dollars per annum, while the experienced ones are offered with a hike of 30 percent and above, depending on their previous withdrawn salary. An experienced candidate can withdraw up to 114,000 to 125,000 dollars per annum based on the skills and expertise he or she has.
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