Networking questions and answers

Everyone are using internet in this advance technology world.Internet helps us in many ways.

Now I am here discuss some Networking based questions and answer which is helps for study and also for interviews.

Q1: What is Network ?

Answer: Network is defined as a set of devices connected to each other using a physical transmission medium.

For 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. In a network, nodes are used to connect two or more networks.

Q2: What is a Node?

Answer: Two or more computers are connected directly by an optical fiber or any other cable. A node is a point where a connection is established. It is a network component that 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.

Q3: What is Network Topology?

Answer: 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?

Answer: The router is a network device that connects two or more network segments. It is used to transfer information from the source to the 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 the OSI reference model?

Answer: Open System Interconnection, the name itself suggests that it is a reference model that 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.

Answer: Given below are the seven layers of OSI Reference Models:

a) Physical Layer (Layer 1): It converts data bits into electrical impulses or radio signals. Example: Ethernet.

b) Data Link Layer (Layer 2): At the Data Link layer, data packets are encoded and decoded into bits and it provides a node to node data transfer. This layer also detects the errors that occurred at Layer 1.

c) Network Layer (Layer 3): This 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”.

d) 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.

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

f) 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.

g) Application Layer (Layer 7): This is the last layer of the OSI Reference Model and is the one that 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.

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

Q8: Explain TCP/IP Model

Answer: 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.

• 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 system connected with each other and it mainly concerns about 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.

Q9: What is HTTP and what port does it use?

Answer: 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.

Q 10: What is HTTPs and what port does it use?

Answer: HTTPs is a Secure HTTP. HTTPs is used for secure communication over a computer network. HTTPs provides authentication of websites that prevents unwanted attacks.

In bi-directional communication, the HTTPs protocol encrypts the communication so that the tampering of the data gets avoided. With the help of an SSL certificate, it verifies if the requested server connection is a valid connection or not. HTTPs use TCP with port 443.

Q 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.

Q 12: What is a Firewall?

Answer: 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 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.

Q 13: What is DNS?

Answer: Domain Name Server (DNS), in a non-professional language and we can call it an 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 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.abc.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 — 111.198.215.78 (note that, this is the imaginary IP address and not the actual IP for the given website) so that you will get redirected to the appropriate destination.

Q 14: What is the difference between a Domain and a Workgroup?

Answer: 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 that are running on an office network or any workplace network belong to the Domain.

Q15: 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 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. It makes the computer network virtually invisible to external users.

Proxy Server also maintains the list of blacklisted websites so that the internal user is automatically prevented from getting easily infected by viruses, worms, etc.

Q 16: What are IP classes and how can you identify the IP class of given an IP address?

Answer: 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 the octet starts with bits 110. Class C has a range from 192.x to 223.x.

Q 17: What is meant by 127.0.0.1 and localhost?

Answer: IP address 127.0.0.1, is reserved for loopback or localhost 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 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 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 localhost are the same things in most of the computer network functioning.

Q 18: What is NIC?

Answer: NIC stands for Network Interface Card. It is also known as 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 be connected to a network.

Each NIC has a MAC address which helps in identifying the computer on a network.

Q 19: What is Data Encapsulation?

Answer: 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 the OSI reference model layer.

The Data Link Layer encapsulates each packet in a frame that 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.

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

Answer: 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 users in the same organization.
• Extranet: External users are allowed or provided with access to use the network application of the organization.

Q 21: What is a VPN?

Answer: 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.

Given below are the 3 types of VPN’s:

1. Access VPN: Access VPN’s provide connectivity to 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.

Q 22: What are Ipconfig and Ifconfig?

Answer: 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 systems. 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.

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