Best Networking Interview Questions for 2023 - IQCode

Understanding the Network: Basics of Computer Networks

When we talk about the network, we refer to an informally interconnected group of entities like people, computers, radio stations, and so on, as defined by Merriam Webster. For instance, Domino's Pizza has a network of 1232 branches across India.

A computer network is a system of peripherals or computers interlinked with each other, establishing a standard communication channel between them. It enables the exchange of different types of data and information.

Computer networks are an essential part of our lives. The Internet is an excellent example of a network of interconnected devices that enable data and information sharing between them. The following are some of the frequently asked basic networking interview questions:

1. How are network types classified?

There are several ways networks can be classified, including:

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

Types of Networks

In computer networking, there are several types of networks, each with specific characteristics and purposes.

1. Local Area Network (LAN) - A LAN is a network that covers a small geographic area, such as an office, building, or campus. It connects devices such as computers, printers, and servers.

2. Wide Area Network (WAN) - A WAN is a network that covers a large geographical area, such as a city, country, or even the entire world. It connects LANs and other networks over long distances.

3. Metropolitan Area Network (MAN) - A MAN is a network that connects multiple LANs within a specific geographic area, such as a city.

4. Wireless Local Area Network (WLAN) - A WLAN is a type of LAN that uses wireless technology to connect devices. It allows devices to connect to the network without the need for cables.

5. Virtual Private Network (VPN) - A VPN is a network that allows users to access a private network over a public network, such as the internet. It provides secure and encrypted communication between devices.

6. Storage Area Network (SAN) - A SAN is a specialized network that provides access to storage devices, such as hard drives and tape libraries. It is used to store and manage large amounts of data.

7. Campus Area Network (CAN) - A CAN is a network that connects multiple buildings within a campus or military base. It is used by universities, hospitals, and other large organizations.

Understanding the different types of networks will help you choose the right one for your needs.

Understanding LAN (Local Area Network)

LAN or Local Area Network is a computer network that connects devices within a relatively small geographical area, such as a home, office building, or school. These devices can include computers, printers, servers, and other peripherals that are all connected via Ethernet cables or wireless connections.

The purpose of a LAN is to allow devices to communicate with each other, share files and resources and ultimately, increase productivity and efficiency. In a LAN, devices can communicate with each other using a variety of protocols such as TCP/IP, NetBEUI, and IPX/SPX.

The most common types of LANs are Ethernet LANs, which use Ethernet cables to connect devices, and wireless LANs, which use radio waves to communicate. Both types of LANs have benefits and drawbacks, and the choice of which one to use depends on the specific needs of the organization or user.

Overall, LANs are an essential part of modern computing and are a crucial component in enabling organizations and individuals to effectively communicate and collaborate with each other.

VPN (Virtual Private Network)

A VPN, or Virtual Private Network, is a secure connection between a user and a remote network. It allows users to send and receive data across shared or public networks as if their devices were directly connected to the private network. VPNs are commonly used to increase privacy and security, especially when accessing the internet from public Wi-Fi networks or when accessing sensitive information. The use of a VPN can also bypass geographical restrictions and censorship, allowing users to access content that may be restricted in their region.

Advantages of Using a VPN

Using a VPN has several advantages including:

1. Enhanced security and privacy
2. Access to blocked websites and restricted content
3. Improved speed and performance when accessing the internet
4. Ability to bypass geographic restrictions and censorship
5. Protection from hackers and online tracking
6. Cost-effective solution for remote access to a private network

Overall, a VPN is a useful tool for anyone who values their online privacy and security, and wants to access the internet freely and securely.

Explanation:

This question is discussing the various types of Virtual Private Networks (VPNs).

Rephrased:

What are the different types of VPNs?

Understanding Nodes and Links

Nodes refer to the individual elements in a data structure that contain data or information. Links are the connections between these nodes, which represent the relationships or dependencies between them. In computer science, nodes and links are commonly used in data structures such as graphs, lists, and trees. By understanding nodes and links, developers can better design and implement efficient algorithms for manipulating and analyzing these data structures.

Understanding Network Topology

In computer networks, a topology refers to the arrangement of different components such as nodes and links that make up the network's infrastructure. It describes how devices are connected to each other and how data flows between them. A good network topology ensures that all nodes in the network can communicate efficiently and effectively. There are several types of network topologies, including the star topology, mesh topology, bus topology, and ring topology. Each type has its own pros and cons, and choosing the right topology for your network depends on factors such as the network size, cost, and performance requirements.

Types of Network Topology

In computer networking, a topology refers to the layout of connected devices or nodes and how they communicate with each other. There are several types of network topologies, including:

• Bus Topology
• Star Topology
• Ring Topology
• Mesh Topology
• Tree Topology

Each topology has its advantages and disadvantages in terms of communication efficiency, cost, ease of installation, and scalability. It is important to choose the right network topology based on the specific needs and constraints of the network being built.

Understanding IPV4 Addresses and Classes

An Internet Protocol Version 4 (IPV4) address is a numerical label assigned to a device connected to a computer network that uses the internet protocol for communication. It serves the purpose of identifying the device and enabling it to communicate with other devices on the network.

There are three main classes of IPV4 addresses:

1. Class A: The first 8 bits of a Class A IPV4 address represent the network identifier, while the remaining 24 bits represent the host identifier. This class of address is ideal for large networks with a large number of hosts.

2. Class B: The first 16 bits of a Class B IPV4 address represent the network identifier, while the remaining 16 bits represent the host identifier. This class of address is ideal for medium-sized networks.

3. Class C: The first 24 bits of a Class C IPV4 address represent the network identifier, while the remaining 8 bits represent the host identifier. This class of address is ideal for small networks.

It's important to note that with the growth of the internet and the increasing number of devices connected to it, the availability of IPV4 addresses is becoming limited. To address this, IPV6 has been developed which uses a larger number of bits for addressing, providing more unique addresses for devices.

Private and Special IP Addresses

In computer networking, an IP address is a unique numeric identifier given to each device connected to the internet. There are various types of IP addresses, including private and special IP addresses.

Private IP addresses are those assigned to devices within a private network, such as a home network or an organization's internal network. These IP addresses are not accessible from the internet and are used for communication within the private network.

Special IP addresses are those designated for specific purposes, such as loopback addresses (127.0.0.1) used for testing network connections on a local machine, multicast addresses used for group communication, and link-local addresses used for communication between devices on the same network segment.

Understanding the different types of IP addresses is important for network administrators and anyone working with computer networks.

Describing the OSI Reference Model

The OSI Reference Model is a conceptual framework that defines the communication functions of a telecommunication or computing system. It stands for Open Systems Interconnection and was developed by the International Organization for Standardization (ISO).

The model consists of seven layers, each having a specific function as follows:

• The Physical layer - deals with the actual transmission of data over the physical medium, such as wires or fiber optic cables.
• The Data Link layer - responsible for error-free data transfer between two directly connected nodes.
• The Network layer - provides a logical addressing scheme for devices across multiple networks.
• The Transport layer - helps ensure reliable and error-free message delivery between end systems.
• The Session layer - sets up, maintains, and terminates sessions between applications.
• The Presentation layer - responsible for data translation and presentation for the application layer.
• The Application layer - provides services directly to the user and includes protocols for services such as email, file transfer, and remote login.

The OSI Reference Model helps ensure that different systems can communicate with each other and that standards are maintained in the design and implementation of communication protocols.

Seven Layers of the OSI Reference Model

The OSI Reference Model has seven layers which are as follows:

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

Each layer has a specific function that is essential for communication between devices in a network. Understanding the OSI Reference Model can help in troubleshooting network issues and designing efficient network architectures.

TCP/IP Reference Model

The TCP/IP reference model is a standard model for communication protocols used on the internet. It consists of four layers:

1. The Application layer, which is responsible for communication between applications through protocols such as HTTP, FTP, and SMTP

2. The Transport layer, which provides end-to-end data transfer over an internet connection through protocols such as TCP and UDP

3. The Internet layer, which is responsible for transferring data between networks through protocols such as IP

4. The Link layer, which is responsible for transmitting data over a physical connection, such as Ethernet or WiFi.

The TCP/IP reference model is often compared to the OSI model, which has seven layers. However, the TCP/IP model is simpler and more widely used for internet communication.

TCP/IP Reference Model: 4 Layers

The TCP/IP reference model consists of four layers, namely:
1. Application Layer
2. Transport Layer
3. Internet Layer
4. Network Access Layer

The Application layer deals with end-user applications; the Transport layer handles end-to-end communication; the Internet layer handles inter-network communication, and the Network Access layer defines how data is physically sent through the network.

Differences between OSI Reference Model and TCP/IP Reference Model

The OSI (Open Systems Interconnection) Reference Model and the TCP/IP (Transmission Control Protocol/Internet Protocol) Reference Model are two different conceptual frameworks used to understand network communication. Here are some key differences between the two models:

- OSI has 7 layers, while TCP/IP has 4 layers.
- OSI has a dedicated presentation layer, which handles data formatting, encryption, and compression. TCP/IP does not have a dedicated presentation layer.
- OSI has a dedicated session layer, which sets up, manages, and terminates sessions between applications. TCP/IP does not have a dedicated session layer.
- OSI's transport layer provides reliable delivery of data between devices, while TCP/IP's transport layer uses a combination of TCP and UDP protocols to provide reliability and speed respectively.
- OSI's network layer handles routing of data between networks, while TCP/IP's network layer uses the Internet Protocol (IP) to route data packets between devices.
- OSI's data link layer provides error detection and correction for data transmissions, while TCP/IP's data link layer includes the Media Access Control (MAC) and Logical Link Control (LLC) layers.
- OSI's physical layer defines the actual physical hardware and connections used in a network, while TCP/IP's physical layer includes the network interface card and corresponding drivers.

HTTP and HTTPS Protocols

HTTP (Hypertext Transfer Protocol) is a protocol used for transmitting data over the internet. It is a stateless protocol that uses TCP (Transmission Control Protocol) to establish a connection with the server. HTTPS (Hypertext Transfer Protocol Secure) is a modified and more secure version of HTTP. It uses SSL/TLS (Secure Sockets Layer/Transport Layer Security) encryption to protect the data transmitted between the client and the server. This encryption makes HTTPS more secure than HTTP and is commonly used for secure transactions such as online banking or shopping.

Overview of SMTP Protocol

SMTP (Simple Mail Transfer Protocol) is a protocol used for sending and receiving email messages between servers. It functions as a communication protocol that allows email messages to be transferred from one server to another over the internet. SMTP is considered as a vital element of email infrastructure and enables the message transfer from email client to the receiving server.

Understanding the Purpose of a Router and How it Differs from a Gateway

A router is a networking device that forwards data packets between computer networks. It is responsible for directing network traffic based on its IP addresses. Essentially, a router determines the best path for data packets to travel from one network to another.

On the other hand, a gateway is a device that connects two different networks that use different protocols. A gateway acts as a bridge between the two networks by facilitating communication between them. Unlike routers, gateways are responsible for translating data from one network to the other so that both networks can understand each other.

In summary, routers are used to direct traffic between networks that use the same protocol, while gateways are used to connect two networks that use different protocols. Both devices play an essential role in maintaining a stable and efficient network environment.

TCP Protocol

The Transmission Control Protocol (TCP) is a widely used transport layer protocol on the Internet. It provides reliable and ordered delivery of data between applications running on hosts communicating over an IP network. TCP is responsible for breaking large data into smaller packets, retransmitting lost packets, and ensuring error-free communication between the sender and receiver. It uses a three-way handshake process for establishing a connection and provides flow control and congestion control mechanisms to ensure efficient data transfer.

Understanding the UDP Protocol

The User Datagram Protocol (UDP) is a connectionless and unreliable transport protocol in computer networking. It operates on top of the Internet Protocol (IP) and is useful for applications that require low-latency and quick transmission of data. Unlike the Transmission Control Protocol (TCP), UDP does not provide any error correction or flow control mechanisms, which makes it a faster option for applications that don't necessarily need those features. However, this also means that UDP packets may arrive out of order or go missing, which can cause issues for some types of applications. UDP is often used for real-time multimedia applications, such as video conferencing and online gaming.

Comparison between TCP and UDP

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are two of the most commonly used protocols for transmitting data over the internet. Here's a comparison between these two protocols:

TCP:
- Provides reliable, ordered, and error-checked delivery of data
- Slower than UDP
- Provides a connection-oriented communication
- More complex than UDP
- Suitable for applications that require high reliability, such as email, file transfer, and web browsing

UDP:
- Provides fast, unreliable delivery of data
- Faster than TCP
- Provides a connectionless communication
- Less complex than TCP
- Suitable for applications that require fast transmission of data, such as online gaming, streaming, and voice communication

In summary, TCP is more reliable but slower, while UDP is faster but less reliable. The choice between these two protocols depends on the specific needs of the application in question.

What is the ICMP Protocol?

ICMP stands for Internet Control Message Protocol. It is a protocol used for sending error messages and operational information about network conditions. ICMP is mainly used for diagnostic and control purposes. It is an essential part of the internet protocol suite and is used by devices such as routers, switches, and firewalls to communicate status and error information. ICMP provides information about network congestion, errors, and the availability of network services. It also helps in troubleshooting network problems by providing error messages related to packet delivery.

Understanding the DHCP Protocol

The Dynamic Host Configuration Protocol (DHCP) is a network protocol used to automatically assign IP addresses and other network configuration parameters to devices on a network. It simplifies network administration by removing the need for manual configuration of each device. DHCP servers provide IP addresses and configuration details to DHCP clients, enabling them to communicate and access network resources.

Understanding the ARP Protocol

The Address Resolution Protocol (ARP) is a communication protocol that allows devices in a network to map their physical addresses to their corresponding IP addresses. This is necessary because computers communicate using IP addresses, but the actual communication happens through hardware addresses, also known as MAC addresses.

The ARP protocol allows a device to broadcast a message on the network to request the hardware address associated with a specific IP address. The device with the corresponding IP address responds with its MAC address, and the requesting device can then use that information to communicate with the other device.

ARP can also be used to resolve conflicts when multiple devices are assigned the same IP address in a network. By broadcasting a request for the MAC address associated with that IP address, the conflicting devices can determine which one should use that IP address and avoid communication errors.

Understanding the FTP Protocol

The FTP protocol, which stands for File Transfer Protocol, is a standard network protocol used for transferring files from one host to another host over a TCP-based network such as the internet. It was developed in the 1970s and is still widely used today.

FTP operates in a client-server model, where the client initiates a connection to the server, and the server responds by providing access to its file system. The client can then perform various actions such as uploading and downloading files, creating and deleting directories, and changing file permissions.

To use FTP, you need an FTP client software that allows you to connect to FTP servers. Most web browsers have built-in FTP support, but there are also standalone FTP client applications that offer more advanced features. Some popular FTP clients include FileZilla, Cyberduck, and WinSCP.

Overall, FTP remains an important protocol for transferring files over the internet and is still widely used in various industries and applications.

Understanding MAC Addresses and their Relation to Network Interface Cards (NICs)

In computer networking, a Media Access Control (MAC) address is a unique identifier assigned to a Network Interface Card (NIC) by the manufacturer. This address is used to uniquely identify each device on a network at the data link layer. The MAC address is a 48-bit address assigned to every NIC and cannot be changed by the user.

NICs on the other hand, are hardware components that enable computers to connect to a network. They are responsible for transmitting data over the network and communicating with other devices on the network. Each NIC is assigned a unique MAC address which is used by the network to identify the device and ensure proper communication between devices.

Understanding the relationship between MAC addresses and NICs is important for troubleshooting network issues as well as securing a network.

Differentiating MAC Address from IP Address

In a network, MAC address and IP address are two different types of addresses used for communication. MAC address is a unique identifier assigned to a network interface controller (NIC) by the manufacturer, while IP address is a unique identifier assigned to a device on a network.

Example of a MAC address: 64:1C:67:5C:2E:FE

Example of an IP address: 192.168.1.100

MAC addresses are used at the local network level, while IP addresses are used at the global network level. MAC addresses are used to identify devices within a local network, while IP addresses are used to identify devices across multiple networks.

To summarize, MAC addresses are used for physical addressing, while IP addresses are used for logical addressing.

Understanding Subnets

A subnet is a part of a larger network that has been separated into smaller parts for better organization, security, and control. Each subnet has a unique identifier known as a subnet mask, which determines the valid IP addresses that can be used within the subnet. Subnets can also be used to manage network traffic by dividing it amongst different subnets, which helps to reduce congestion and improve network performance. Overall, subnets are a crucial concept in network architecture and management.

Comparison between Hub and Switch

When it comes to networking devices, hubs and switches play a significant role in connecting devices in a LAN network. But they have important differences that should be considered before selecting the appropriate device for a networking setup.

/**
 * Hub class represents a networking hub device
 */
class Hub {
  function __construct() {
    echo "Hub device initialized";
  }

  public function broadcast($message) {
    // broadcast message to all connected devices
    echo "Broadcasting message: " . $message;
  }
}

/**
 * Switch class represents a networking switch device
 */
class Switch {
  private $connectedDevices;

  function __construct() {
    $this->connectedDevices = array();
    echo "Switch device initialized";
  }

  public function connect($device) {
    // connect device to switch
    array_push($this->connectedDevices, $device);
    echo $device . " connected to switch";
  }

  public function send($message, $device) {
    // send message to selected device
    echo "Sending message: " . $message . " to device: " . $device;
  }
}

// create hub device
$hub = new Hub();
// broadcast message to all connected devices
$hub->broadcast("Hello world!");

// create switch device
$switch = new Switch();
// connect devices to switch
$switch->connect("server");
$switch->connect("printer");
// send message to selected device
$switch->send("Print document", "printer");

In summary, a hub is a simpler and less intelligent device that broadcasts a message to all devices connected to it, while a switch is a more advanced device that sends a message only to the targeted device. Therefore, switches are typically used in network setups where efficiency and security are as important as speed of data transfer.

Differences between ipconfig and ifconfig

IPconfig is a command-line tool used in Windows systems to display the IP address, subnet mask, and default gateway for all network adapters on a device. On the other hand, ifconfig is a command-line tool mainly used in Unix-based operating systems such as Linux, macOS, and FreeBSD to configure and display information about network interfaces. Overall, both tools serve similar purposes but are designed for different operating systems.

Explanation of Firewall

A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Its primary objective is to prevent unauthorized access to or from a private network while allowing authorized communications to pass through. Firewalls can either be hardware devices or software programs that are installed on computers or servers. They are essential in protecting networks from cyber threats and attacks.

Understanding Unicasting, Anycasting, Multicasting, and Broadcasting

Unicasting, anycasting, multicasting, and broadcasting are terms commonly used in networking to refer to different methods of transmitting data on a network. Unicasting is a method of communication where data is sent from one sender to one receiver. Anycasting is similar to unicasting in that data is also sent from one sender, but it can be received by multiple recipients. Multicasting is a method of communication where data is sent from one sender to many recipients who have expressed interest in receiving the data. Broadcasting, on the other hand, is a method of communication where data is sent to all devices on a network regardless of whether they have expressed interest in receiving it or not. Each of these methods has its advantages and limitations, and their use depends on the specific network requirements.

// Example of Unicasting in Java

// Create a DatagramSocket object to send data
DatagramSocket senderSocket = new DatagramSocket();

// Specify the IP address and port number of the receiver
InetAddress receiverAddress = InetAddress.getByName("192.168.1.100");
int receiverPort = 5000;

// Create a message to send
String message = "Hello, this is a unicasting message.";
byte[] messageBytes = message.getBytes();

// Create a DatagramPacket object containing the message and its destination
DatagramPacket packet = new DatagramPacket(messageBytes, messageBytes.length, receiverAddress, receiverPort);

// Send the packet
senderSocket.send(packet);

// Close the socket
senderSocket.close();

Exploring what happens when you enter "google.com" in a web browser

When you enter "google.com" in a web browser, the browser sends a request to the Google servers to retrieve the website's files. Then, Google's servers respond by sending back the HTML, CSS, and JavaScript files necessary to display the Google homepage. The browser then renders the webpage and displays it on the screen. From there, you can search for anything you want on Google or navigate to other pages on the site.