55+ Top Networking Interview Questions and Answers for All Skill Levels in 2025

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In 2025, India’s tech industry is projected to grow 15–20%, creating high demand for roles in cloud computing, cybersecurity, and AI. Notably, 85% of these positions are filled through networking, underscoring the importance of learning networking concepts.

The best way to prepare for networking interview questions and answers in 2025 is to practice with real-world examples. Companies like Cisco, TCS, Infosys, and HCL now expect you to know how to handle protocols, troubleshoot issues, and work with tools like Wireshark, Cisco Packet Tracer, and GNS3. 

With cloud services, cybersecurity, and remote support on the rise, your networking knowledge must be sharp and practical. Hiring managers don’t just ask theory; they test how you’d handle real systems.

In this blog, you’ll find 55+ networking interview questions and answers, grouped by skill level, so you can confidently walk into your next interview.

If you’re aiming to build a solid career in tech, start by building strong fundamentals in software development and networking. upGrad’s Software Development courses include structured interview prep, real-world projects, and access to an exclusive job portal. With tools like Python, Git, and SQL, and an average salary hike of up to 66%, you’ll gain the skills top employers like TCS, Infosys, and Accenture actively seek.

Essential Networking Interview Questions and Answers for Beginners

Learning the basics of networking is crucial for roles like IT support, network technician, and junior system admin. These networking interview questions and answers cover key topics such as the OSI model, TCP/IP, subnetting, DHCP, and basic switching and routing. You’ll also review real-life scenarios like identifying IP conflicts and configuring static routes. 

To build the foundations for these networking roles, here are some of upGrad’s most relevant programs:

• Professional Certificate Program in Cloud Computing and DevOps
• AI-Powered Full Stack Development Certification Course by IIITB
• Generative AI Mastery Certificate for Software Development

Now, let's explore key networking interview questions that recruiters often ask beginners.

1. Which Two Technologies Would You Use To Connect Two Remote Offices?

To connect two remote offices, you must use reliable and secure networking technologies. The choice depends on factors such as bandwidth, security, and cost.

Common Technologies for Remote Office Connectivity:

• Virtual Private Network (VPN): Encrypts data over the internet. It's widely used by companies like Zoho and Freshworks to securely connect branch offices without high infrastructure costs.
• Multiprotocol Label Switching (MPLS): Offers high-speed, low-latency connections with traffic prioritization. Banks like HDFC and ICICI often rely on MPLS for stable and secure internal communications.

Both VPN and MPLS are essential for building enterprise-grade remote connectivity solutions.

Also Read: Computer Networking Basics: Network Types, Technologies, Topologies, Pros and Cons

2. How Would You Define Internetworking?

Internetworking is the process of connecting two or more distinct networks to allow smooth data exchange across them. It’s what lets devices on different LANs or WANs communicate with each other, forming the foundation of the internet and large-scale enterprise systems.

Key Aspects of Internetworking:

• Routing: Moves data across networks using routers. For example, Amazon’s internal services use routing protocols like BGP and OSPF to manage traffic across global data centers.
• Bridging: Connects separate network segments at the data link layer, often used in campus networks to extend reach.
• Protocols: Uses standards like TCP/IP, which define how data is packaged, addressed, transmitted, and received.

Internetworking is what allows services like Gmail or Office 365 to operate across the globe, regardless of device or location.

Also Read: A Comprehensive Guide to Understanding the Different Types of Data

3. What Are The Primary Software (User Support) Layers In The OSI Model?

The OSI model organizes network communication into seven layers. The top three, Application, Presentation, and Session, are known as the software or user support layers because they directly interact with user-facing applications.

Primary Software (User Support) Layers:

• Application Layer (Layer 7): Interfaces directly with end-user software like browsers (Chrome, Firefox), email clients (Outlook), and messaging apps (Slack).
• Presentation Layer (Layer 6): Handles data translation, encryption, and compression. For example, it converts encrypted HTTPS traffic into readable content on your screen.
• Session Layer (Layer 5): Manages communication sessions between applications. It’s responsible for establishing, maintaining, and terminating sessions, for instance, keeping your Zoom call stable.

These layers ensure users experience smooth, secure, and reliable access to networked services.

4. What Are The Main Hardware (Network Support) Layers In The OSI Model?

The lower layers of the OSI model deal with physical connections, data framing, and routing, core elements of network infrastructure. These layers ensure that data can move across hardware devices reliably and efficiently.

Main Hardware (Network Support) Layers:

• Physical Layer (Layer 1): Transfers raw bits over cables, fiber optics, or wireless. Devices like Ethernet cables, network interface cards (NICs), and Wi-Fi antennas operate here.
• Data Link Layer (Layer 2): Uses MAC addresses for device identification and handles error checking. Switches and access points rely on this layer to forward frames.
• Network Layer (Layer 3): Handles IP addressing and routing. Routers from brands like Cisco and Juniper work at this layer to move packets across different networks.

Together, these layers form the hardware backbone of any network setup.

Also Read: Comprehensive Guide to IoT Architecture and Layers: Components, Applications and More

5. How Does The HTTPS Protocol Work And Why Is It Important?

HyperText Transfer Protocol Secure (HTTPS) ensures secure communication between web browsers and servers using SSL/TLS encryption. It protects data from interception, verifies website authenticity, and ensures data integrity.

How HTTPS Works:

1. TLS/SSL Handshake – When a browser connects to a website, it initiates a handshake, where the server presents its SSL certificate. The browser verifies this certificate through a trusted Certificate Authority (CA).
2. Asymmetric Encryption – During the handshake, the client and server use public-key cryptography to securely exchange a session key.
3. Symmetric Encryption – Once the session key is shared, all communication is encrypted using faster symmetric encryption.

HTTPS prevents eavesdropping, tampering, and impersonation, making it essential for secure online interactions.

Also Read: What is DES (Data Encryption Standard)? DES Algorithm Explained

6. What Key Services Does The Application Layer Provide In The Internet Model?

The application layer delivers core services that users interact with daily. It enables communication between software applications over a network using standard protocols.

Application Layer Services:

• Email Services: Uses protocols like SMTP, IMAP, and POP3. Outlook and Gmail rely on these to send, receive, and sync emails.
• File Transfer: Supports file sharing with protocols like FTP, SFTP, and HTTP. Tools like FileZilla and browsers depend on this for uploads and downloads.
• Remote Access: Uses SSH and Telnet to access remote systems. System admins often use PuTTY or OpenSSH to manage servers securely.

Learning these services helps you troubleshoot user-facing network issues faster.

Also Read: File Handling in Java: How to Work with Java Files?

7. At Which OSI Layer Are Headers And Trailers Added To A Packet?

At the Data Link Layer, both headers and trailers are added to frames before transmission. These components help ensure the data reaches the right device and arrives intact.

Understanding this structure is key when working with tools like Wireshark or managing Ethernet-based networks.

Also Read: Top 10 Data Modeling Tools You Must Know

8. Describe The Process As Data Moves From The Lower To The Upper Layers In The OSI Model.

When data reaches the receiving device, it moves up through the OSI model; each layer unpacks the information added during transmission.

Process of Upward Data Movement:

• Physical Layer (Layer 1): Converts electrical or optical signals into binary bits. Example: A Wi-Fi router receives the signal from a laptop.
• Data Link Layer (Layer 2): Strips off headers and trailers. It checks the Frame Check Sequence (FCS) to ensure data isn’t corrupted.
• Network Layer (Layer 3): Reads the IP address, determines if the data is for the current device, and passes it on.

This unpacking continues through higher layers until the original message is delivered to the application.

Also Read: Integrity Constraints in DBMS: Purpose, Types, Challenges, and Best Practices to Know in 2025

9. Explain What Happens When Data Moves From The Upper To The Lower Layers In The OSI Model.

When you send data, it flows downward through the OSI model. Each layer adds its own headers or instructions to prepare the data for delivery.

Downward Data Movement:

• Application Layer (Layer 7): Prepares the message. For example, a browser sends an HTTP request to load a webpage.
• Transport Layer (Layer 4): Splits data into segments and assigns port numbers (e.g., 80 for HTTP, 443 for HTTPS).
• Network Layer (Layer 3): Adds IP addresses. Routers use this to route packets toward the destination.

This process continues until the data reaches the physical layer and is transmitted as signals.

Also Read: What Is Attenuation in Data Communication and How is it Caused?

10. What Is A Zone-Based Firewall, And How Does It Enhance Security?

A Zone-Based Firewall (ZBF) improves network security by dividing the network into zones and controlling traffic between them. Instead of applying rules to interfaces, ZBF applies policies between zones, making it more flexible and secure.

Benefits of ZBF:

• Traffic Segmentation: Separates internal, external, and DMZ networks. For example, isolate public web servers from internal HR systems.
• Policy Enforcement: Blocks or allows traffic based on zone relationships. For instance, traffic from the internet to a database zone can be blocked by default.
• Granular Control: Supports deep packet inspection for application-specific rules, which are used in Cisco routers and firewalls for enterprise-grade control.

ZBF is widely used in modern enterprise networks for layered defense.

Also Read: Difference between Hub and Switch

11. Define A Server Farm And Its Primary Function.

A server farm is a group of connected servers that work together to support large-scale applications and services. These are commonly used in data centers by companies like Google, AWS, and Meta to manage high-volume workloads.

Knowing how server farms operate helps you understand how cloud infrastructure and enterprise systems scale efficiently.

Also Read: What is Client Server Architecture? Components, Types, Examples Explained

12. What Are The Three Main Methods Of User Authentication?

User authentication confirms a person’s identity before granting access to systems or data. It protects networks from unauthorized use.

Primary Authentication Methods:

• Something You Know: Examples include passwords, PINs, and security questions. Used in most login systems like Gmail or company portals.
• Something You Have: Devices such as smart cards, hardware tokens, or mobile authenticator apps like Google Authenticator or Duo.
• Something You Are: Biometrics like fingerprints, face scans, or voice recognition are common in smartphones and secure access points.

Stronger systems often use two or more methods together, known as multi-factor authentication (MFA).

Also Read: What Is a Network Administrator? A Complete Career Guide to Skills, Jobs, and Salaries

13. Explain The Concepts Of Confidentiality, Integrity, And Availability.

These three principles, known as the CIA Triad, form the foundation of network security. Have a look at the purpose of Confidentiality, Integrity, And Availability.

Also Read: Is Cyber Security Easy to Learn? : Tips to Become A Cybersecurity Expert

14. What Is A VPN And How Does It Secure Data Communications?

A Virtual Private Network (VPN) lets users connect to private networks over the internet while keeping their data secure. It’s widely used by remote workers, businesses, and anyone needing safe access to internal systems.

How a VPN Secures Data:

• Encryption: Uses protocols like IPSec, OpenVPN, or WireGuard to scramble data. This stops hackers from reading it during transmission.
• Tunneling: Wraps data in encrypted tunnels. For example, Cisco AnyConnect and NordVPN use tunneling to protect traffic end-to-end.
• Anonymity: Masks your IP address. This hides your location and helps prevent targeted cyberattacks.

VPNs are essential for secure remote work, especially in cloud-based and BYOD environments.

Also Read: What is Network Address Translation (NAT) in Networking? A Ultimate Guide

15. Compare And Contrast Symmetric And Asymmetric Encryption.

Encryption protects data by converting it into unreadable code. The main difference between symmetric and asymmetric encryption is how they use keys.

Contrast Symmetric And Asymmetric Encryption:

16. At Which Layer Does IPsec Operate And What Does It Achieve?

IPsec operates at the Network Layer (Layer 3) of the OSI model. It protects IP traffic between two endpoints, often used in site-to-site and remote-access VPNs.

What IPsec Achieves:

• Data Integrity: Uses Authentication Header (AH) to detect tampering. Common in secure banking networks.
• Encryption: Applies ESP (Encapsulating Security Payload) to encrypt packets. Tools like strongSwan and Cisco ASA support this.
• Authentication: Verifies identity using digital certificates or pre-shared keys. Helps prevent spoofing and unauthorized access.

IPsec is a key part of secure tunneling protocols in enterprise VPNs and cloud networking.

Also Read: Introduction to Cyber Security: Everything Beginners Need to Know

17. What Is Tunnel Mode In IPsec, And When Is It Used?

Tunnel Mode in IPsec encrypts the entire original IP packet, including headers. It then wraps it in a new packet with a fresh IP header for secure delivery across untrusted networks.

When Tunnel Mode Is Used:

• Site-to-Site VPNs: Connects offices in different locations. Used by companies like Infosys to protect internal traffic.
• Remote Access VPNs: Lets remote employees securely access company systems over public networks.
• Multi-Network Security: Encrypts traffic between zones in cloud setups (e.g., AWS VPC-to-VPC communication).

Tunnel Mode ensures end-to-end protection without exposing internal IP addresses.

Also Read: What is End-to-End Encryption? How It Works, and Why We Need It

18. How Do Digital Signatures Work To Ensure Data Authenticity?

Digital signatures verify that a message or file comes from a trusted sender and hasn’t been altered. They use hashing and encryption to ensure authenticity and integrity.

How Digital Signatures Work:

• Hashing: Creates a unique fingerprint of the message using algorithms like SHA-256.
• Encryption: The sender encrypts the hash with their private key. This forms the digital signature.
• Verification: The recipient decrypts the signature using the sender’s public key and compares it with a new hash of the message.

Used in software distribution, legal documents, and SSL certificates, digital signatures are a core part of cybersecurity.

Also Read: Cryptography in Cybersecurity: Definition, Types & Examples

19. What Is Authorization, And Why Is It Critical In Network Security?

Authorization defines what a user can access after their identity is verified. It ensures users only interact with data, systems, or services they’re allowed to use.

Importance of Authorization:

• Access Control: Limits access based on roles. For example, HR staff can view employee records, but not server logs.
• Security Enforcement: Prevents users from modifying or viewing restricted data. Used in systems like AWS IAM and Active Directory.

• Policy Compliance: Supports audits by enforcing access policies and logging activity.

  Authorization is key to preventing internal threats and maintaining secure operations across all departments.

Also Read: What is Big Data? A Comprehensive Guide to Big Data and Big Data Analytics

20. Differentiate Between An Intrusion Prevention System (IPS) And A Firewall.

Both firewalls and IPS help secure networks, but they focus on different threats and operate at different layers.

While a firewall acts as a gatekeeper, an IPS acts as a security guard, actively watching and stopping suspicious behavior.

Also Read: What is an Intrusion Detection System (IDS)? Techniques, Types & Applications

21. What Is IP Spoofing And What Security Risks Does It Pose?

IP spoofing is when an attacker fakes the source IP address in a packet to appear as a trusted system. It’s used to hide identity or bypass security controls.

Security Risks of IP Spoofing:

• DDoS Attacks: Attackers flood servers with fake traffic, making it hard to trace or block. Often seen in botnet attacks.
• Session Hijacking: Hackers take over active sessions, especially in unsecured networks.
• Firewall Evasion: Spoofed packets can bypass basic IP-based filters and reach internal systems.

IP spoofing is a key technique in many advanced persistent threats and requires strong network-level defenses to stop.

22. Define Threat, Vulnerability, And Risk In The Context Of Network Security.

These three terms are central to identifying and managing cybersecurity threats within any network.

Understanding these helps you prioritize security controls and reduce exposure to cyber threats.

Also Read: Cyber Security Threats: What are they and How to Avoid

23. What Is The Primary Role Of A DNS Server In A Network?

A DNS (Domain Name System) server converts domain names into IP addresses so devices can locate each other on a network. It’s a critical part of how the internet functions.

Functions of a DNS Server:

• Name Resolution: Translates domains like www.google.com into IP addresses like 142.250.192.14.
• Load Balancing: Spreads incoming traffic across servers. Used by platforms like YouTube and Netflix to manage high loads.

• Caching: Stores recent lookups to speed up future queries and reduce external DNS traffic.

  Without DNS, users would need to remember IP addresses to access websites.

  Curious about how blockchain impacts networking? Explore upGrad’s Introduction to NFTs course to understand how decentralized networks handle data, resolve identities, and maintain security, concepts closely tied to DNS and routing. This free course covers blockchain fundamentals, NFT metadata, and smart contract interactions using real examples. 

Intermediate Networking Interview Questions for IT Professionals

Networking skills evolve with experience, making intermediate knowledge crucial for career advancement. At this stage, you must grasp essential concepts like TCP/IP, network topologies, routing, switching, and troubleshooting. 

These topics ensure you can handle real-world networking challenges efficiently. The following networking interview questions and answers assess your ability to apply these concepts effectively.

To deepen your understanding, let’s explore technical questions on protocols, network design, error handling, and advanced data transmission techniques.

24. Which Protocol and Port Are Used by DNS, and Why?

DNS (Domain Name System) primarily uses UDP on port 53 for its lightweight, fast query resolution. However, it switches to TCP on port 53 for large queries or zone transfers.

Key Reasons:

• UDP for Speed: DNS queries are small, requiring quick resolution without connection overhead.
• TCP for Reliability: When DNS transfers large amounts of data, TCP ensures delivery.

This dual-use of UDP and TCP enhances efficiency and reliability in network communications.

Also Read: 25+ Best Data Migration Tools in 2025: Key Benefits and How to Select the Right One for Your Require

25. Where Does the Transmission Media Fit Into the OSI Model, and Why Is Its Placement Important?

Transmission media operate at Layer 1 (the Physical Layer) of the OSI model. This layer handles the actual movement of data through cables or wireless signals.

Importance of Its Placement:

• Foundation of Communication: It defines how bits travel across the network. For example, fiber optics offer higher speed and lower interference than copper cables.
• Direct Impact on Performance: Bandwidth, signal strength, and latency depend on the chosen medium, whether it’s Ethernet, coaxial cable, or Wi-Fi.

Choosing the right transmission media is critical when building fast, stable, and scalable network infrastructure.

Also Read: What Is Information Technology? Types, Benefits, and Certifications

26. Why Is Twisting Used in Twisted-Pair Cables, and What Problem Does It Solve?

Twisted-pair cables are designed to reduce electromagnetic interference (EMI) and crosstalk by twisting two insulated wires together. This technique is widely used in Ethernet cabling like Cat5e and Cat6.

How It Works:

• Cancels Out Noise: Twisting ensures that interference affects both wires equally, canceling out unwanted signals.
• Enhances Signal Quality: Reduces distortion from nearby cables and devices, keeping data intact during transmission.

Benefits of Twisting in Cables:

This makes twisted-pair cables ideal for office networks, VoIP systems, and high-speed internet setups.

27. What Types of Errors Can Go Undetected by a Checksum?

Checksums are useful for spotting many transmission errors, but they’re not foolproof. Some error types can pass through undetected, which is why stronger methods like CRC are often used in critical systems.

Undetected Types of Errors in Checksums:

Understanding these limitations helps when evaluating which error-checking method to use for reliable data transmission.

Also Read: What is Debugging in Coding: Tools & Techniques for Debugging Explained

28. Which Multiplexing Technique Is Typically Used in Fiber-Optic Communications?

Fiber-optic networks use Wavelength Division Multiplexing (WDM) to transmit multiple signals simultaneously over different light wavelengths.

Why WDM?

• Maximizes Bandwidth: Sends multiple signals through a single fiber using separate light wavelengths, commonly used by ISPs and data centers.
• Efficient Data Transmission: Reduces congestion and supports more users without adding new physical lines.

Thus, WDM enhances fiber-optic network efficiency, making it the preferred choice for high-speed data transmission.

Also Read: Data vs Information: A guide to understanding the key differences

29. What Are the Advantages of Using Fiber Optic Cables in Modern Networks?

Fiber optic cables outperform traditional copper cables due to their higher speed, bandwidth, and immunity to interference.

Key Advantages:

• High-Speed Data Transfer: Supports speeds up to 100 Gbps or more. Used by ISPs, cloud providers, and financial firms for fast data movement.
• Immunity to EMI: Doesn’t carry electrical signals, so it’s unaffected by electromagnetic interference from nearby devices.
• Long Transmission Distance: Maintains signal strength over kilometers, ideal for data centers, campuses, and intercity networks.

Fiber is essential for scaling up modern infrastructure, especially in 5G and cloud computing environments.

30. How Are Analog Signals Combined Using Multiplexing Techniques?

Analog signals are combined using Frequency Division Multiplexing (FDM). This method allows multiple signals to travel over a single channel by assigning each one a unique frequency range.

How FDM Works:

• Different Frequency Bands: Each signal operates on its own frequency to avoid overlap.
• Simultaneous Transmission: All signals are sent at once without interference.

Techniques for Multiplexing Analog Signals:

FDM is essential for efficient use of analog bandwidth in telecom, broadcasting, and cable systems.

Also Read: Basic CNN Architecture: A Detailed Explanation of the 5 Layers in Convolutional Neural Networks

31. What Multiplexing Method Is Applied to Digital Signals?

In digital communication, Time Division Multiplexing (TDM) is the primary method used to transmit multiple signals over a single line. It assigns each signal a dedicated time slot on a shared channel, common in telecom, VoIP, and digital broadcasting.

Why TDM?

• Efficient Data Allocation: TDM gives each digital stream a fixed slot in a repeating cycle. For example, traditional T1 lines in enterprise telephony use TDM to transmit 24 voice channels over one line.

No Frequency Overlap: Unlike analog systems, TDM sends data at different time intervals using the same frequency. This reduces interference and simplifies hardware design.

Digital Multiplexing Techniques:

These methods are essential for managing bandwidth in modern networks without needing extra physical lines.

Also Read: What is a Data Acquisition System in Machine Learning?

32. Is It Possible to Load-Balance IP Multicast, and If So, How?

Yes, IP multicast load balancing is possible but requires specialized routing techniques. Unlike unicast, multicast routing depends on PIM (Protocol Independent Multicast) and IGMP.

Methods for Multicast Load Balancing:

• Equal-Cost Multipath (ECMP): Uses multiple paths with equal cost to distribute multicast traffic.
• Anycast RP (Rendezvous Point): Distributes multicast traffic across multiple routers for redundancy.
• Multicast Source Discovery Protocol (MSDP): Allows inter-domain multicast load sharing.

Some different Multicast Load Balancing Methods are:

Also Read: How Does IoT Work? Top Applications of IoT

33. What Is the Cisco Group Management Protocol (CGMP) and What Is Its Purpose?

Cisco Group Management Protocol (CGMP) is a Cisco-specific protocol that optimizes multicast traffic on Layer 2 switches. It prevents unnecessary multicast flooding by ensuring traffic reaches only interested receivers.

CGMP’s Key Benefits:

• Efficient Multicast Delivery: Instead of flooding all ports, CGMP directs multicast streams (like live video or financial feeds) only to subscribed hosts.
• Better Network Performance: Reduces load on endpoints that don’t need multicast traffic, especially in enterprise video conferencing and IPTV setups.
• Integration with IGMP: Works with routers running IGMP (Internet Group Management Protocol) to update switch port mappings for multicast groups in real time.

CGMP is useful in large Layer 2 networks where multicast traffic would otherwise degrade overall performance.

34. How Would You Explain Multicast and Its Benefits in a Network?

Multicast is a communication method where one sender transmits data to multiple specific receivers at once, using a single stream. It’s commonly used in applications where the same data needs to reach many users simultaneously.

Key Benefits of Multicast:

• Efficient Bandwidth Usage: Sends one copy of the data, even if 100 users are watching the same stream. Used in platforms like Zoom Webinars and live stock market feeds.
• Scalability: Supports thousands of users without adding load on the sender. Common in IPTV systems, online classrooms, and real-time trading platforms.
• Lower Network Congestion: Reduces duplicate traffic on routers and switches, which improves overall network performance.

Multicast uses IP address ranges like 224.0.0.0 to 239.255.255.255 and protocols like IGMP and PIM to manage group memberships.

Also Read: Top 20+ Networking Certifications for Your IT Career in 2025: A Complete Guide

35. Compare Bluetooth and WiFi in Terms of Functionality and Typical Use Cases.

Comparison of Bluetooth and WiFi:

Both technologies are essential but operate in different network layers and application scenarios.

Also Read: What Are IOT Devices?: Definition, Uses, Types

36. What Is a Reverse Proxy and How Does It Function Within a Network?

A reverse proxy is a server that intercepts requests from clients and forwards them to the appropriate backend server. It’s widely used in web applications, APIs, and cloud environments.

Functions of a Reverse Proxy:

• Enhances Security: Hides internal server IPs and blocks direct access. Common in setups using Nginx or AWS Application Load Balancer.
• Improves Performance: Caches static content, compresses responses, and handles SSL termination.
• Load Balancing: Distributes traffic evenly across multiple backend servers to prevent overload.

Reverse proxies also support authentication, rate limiting, and failover handling in high-traffic environments.

Also Read: What Does a Back-End Developer Do?

37. Discuss the Importance of Addressing in the Context of a Datagram Network.

In datagram networks like the Internet, data is sent as independent packets with no fixed path. Addressing plays a key role in getting each packet to the right destination.

Why Addressing Matters in Datagram Networks:

• Packet Delivery: Each packet includes a unique destination IP, allowing routers to forward it correctly. Used in protocols like UDP and IP.
• Routing Decisions: Routers examine destination IPs in real time to decide the next hop, which is essential in tools like traceroute or routing tables.

• Fault Tolerance: Since no connection is established, packets can take different routes if one fails. This keeps services like VoIP and DNS resilient during network issues.

  Accurate addressing ensures end-to-end communication without relying on persistent links.

Also Read: Python Network Programming: Features, Internet Modules & Networking Terminologies

38. Can a Routing Table in a Datagram Network Have Duplicate Entries for the Same Destination? Explain.

Yes, a routing table in a datagram network can contain multiple entries for the same destination. This is common in networks using load balancing or redundancy strategies.

When Duplicate Entries Occur:

• Equal-Cost Multipath (ECMP): Allows multiple next-hop routes with the same metric. Routers like Cisco and Juniper use ECMP to balance traffic across links.
• Dynamic Routing Protocols: Protocols like OSPF, BGP, and EIGRP automatically insert alternative routes for the same destination network.
• Failover Mechanisms: Backup routes ensure continued packet delivery if the primary path fails.

Routing Table Example with Duplicate Entries:

These entries allow routers to distribute traffic or switch paths instantly during link failure.

Also Read: Routing in ReactJS for Beginners

39. What Mathematical Operations Are Typically Used in Checksum Calculations?

Checksums use simple arithmetic and bitwise operations to detect errors in transmitted data. These methods help ensure the integrity of packets during transmission.

Common Operations in Checksum Calculations:

• One’s Complement Addition: Adds binary values together. If there’s overflow, it wraps around and adds it back. Used in TCP/IP header checksums.
• Modulo-N Arithmetic: Ensures the result stays within a fixed bit length. Prevents overflow errors during large data summations.
• Bitwise XOR: Flips bits based on parity. While not used in classic checksums, it appears in CRC and parity-based error detection.

Checksum Calculation Methods:

These techniques make checksums fast and lightweight, though limited in detecting complex errors.

Also Read: Difference between Algorithm and Program

40. Define Piggybacking in Networking and Provide an Example of Its Use.

Piggybacking is a technique used in bidirectional communication where acknowledgment (ACK) messages are combined with outgoing data. This reduces the number of packets sent and improves overall network efficiency.

Example:
In TCP communication, if Host A sends data to Host B, and Host B also has data to send back, it doesn’t send a separate ACK. Instead, it includes the ACK in its outbound data packet. This reduces overhead, especially in chat apps, file transfers, or VoIP systems.

Piggybacking vs. Separate ACKs:

Piggybacking is built into TCP for optimized performance in interactive, real-time communication.

41. Discuss the Pros and Cons of Using Piggybacking in Network Communications.

Piggybacking is used in protocols like TCP to combine acknowledgment (ACK) packets with outgoing data. It reduces traffic on the network but comes with trade-offs, especially in asymmetric or time-sensitive environments.

Pros of Piggybacking:

• Reduces ACK Overhead: Instead of sending an empty TCP ACK, it’s bundled with outbound data. For example, in a two-way file sync tool like rsync, this cuts packet count nearly in half.
• Optimizes Bandwidth Usage: By maximizing each packet’s payload, it improves throughput, useful in high-latency links like satellite internet or cross-border data centers.

Cons of Piggybacking:

• Delayed ACKs: If the receiver has no immediate data to send back, it holds the ACK. In live multiplayer games or stock trading platforms, even milliseconds of delay can affect performance.
• Not Suitable for Unidirectional Traffic: In use cases like video streaming or telemetry sensors, where data flows one way, piggybacking fails to trigger timely ACKs, leading to retransmissions.

Pros and Cons of Piggybacking:

Piggybacking works best in chat apps, file transfers, and secure shell (SSH) sessions, but should be avoided in real-time or one-way communication environments.

42. Which Method Is Commonly Employed in Byte-Oriented Protocols?

Byte stuffing is the standard method used in byte-oriented protocols like PPP (Point-to-Point Protocol) and HDLC (High-Level Data Link Control). It prevents data from being confused with control characters that mark the start or end of a frame.

How Byte Stuffing Works:

• Adds Escape Characters: Inserts a predefined escape byte (like ESC) before special characters such as FLAG or ESC itself.
• Prevents Data Misinterpretation: Ensures the receiver doesn’t mistake data bytes for frame delimiters.

Byte Stuffing Example:

If the original data contains 01111110 (the HDLC frame delimiter), byte stuffing modifies the frame like this:

This technique allows protocols to send all possible byte values, including those used as control signals, without breaking frame boundaries.

Now that you’ve covered the intermediate concepts, let’s move into advanced networking interview questions designed for seasoned engineers working with large-scale, high-performance networks.

Advanced Networking Interview Questions for Seasoned Engineers

Senior network engineers must possess deep expertise in advanced protocols, security strategies, and performance optimization. Leadership roles demand a strong understanding of complex network architectures and the ability to implement scalable solutions. A strong grasp of advanced networking interview questions is crucial for career advancement.

As you explore these networking interview questions and answers, you will refine your technical expertise and problem-solving skills. Now, let’s examine key advanced topics, starting with OFDM.

43. Define Orthogonal Frequency-Division Multiplexing (OFDM) And Its Role In Modern Networks

Orthogonal Frequency-Division Multiplexing (OFDM) is a digital transmission technique that divides a signal into multiple narrowband subcarriers, transmitting them simultaneously. This approach enhances data rates and reduces interference.

Role In Modern Networks:

• High Data Efficiency: OFDM increases spectral efficiency, making it ideal for wireless and broadband applications.
• Resistance To Interference: The orthogonal nature of subcarriers reduces inter-symbol interference (ISI).
• Wide Use In Technologies: Used in Wi-Fi (802.11), LTE, and 5G for high-speed data transmission.

Also Read: Data Analytics Life Cycle Explained

44. What Is A Transparent Bridge, And How Does It Differ From Other Network Bridges?

A transparent bridge is a Layer 2 device that connects multiple network segments without altering the frame content. It learns MAC addresses and forwards frames efficiently.

Key Differences:

Transparent bridges play a critical role in seamless networking interview questions related to LAN design. 

Also Read: Convolutional Neural Networks: Ultimate Guide for Beginners in 2024

45. What Are The Minimum And Maximum Sizes Of An ICMPv4 Packet, And Why Do These Limits Exist?

ICMPv4 (Internet Control Message Protocol for IPv4) is used for diagnostics and error reporting, such as with the ping and traceroute commands. Packet size limits are defined by the underlying IPv4 protocol.

Size Constraints:

• Minimum Size: 8 bytes (ICMP header only). This includes the type, code, checksum, and basic control fields, used for error messages like "Destination Unreachable."
• Maximum Size: 65,535 bytes (total IPv4 packet size, including the IP header). In practice, most systems limit ICMP payloads to avoid fragmentation. Windows typically defaults to 32 bytes, while Linux uses 56 bytes.

These boundaries ensure ICMP messages stay lightweight and do not overload the network during routine diagnostics or error reporting.

Also Read: Career in Software Development: 13 Various Job Roles To Choose From

46. Why Might One Choose OSPF Over RIP For Routing In A Fast-Paced Network Environment?

In high-performance or enterprise networks, OSPF (Open Shortest Path First) is preferred over RIP (Routing Information Protocol) due to its speed, scalability, and efficiency.

OSPF Advantages:

• Scalability: Supports large, complex networks using areas and hierarchical design. Common in large enterprises and ISPs.
• Faster Convergence: Detects network changes quickly and recalculates paths using link-state updates, not slow periodic broadcasts like RIP.

• Efficiency: Sends updates only when topology changes, reducing bandwidth use. RIP floods updates every 30 seconds, which can strain links.

  For environments with many routers, VLANs, or rapid changes, like financial data centers or university campuses, OSPF is the smarter, more reliable choice.

47. Identify The Two Main Categories Of DNS Messages And Describe Their Functions.

DNS messages are crucial for resolving domain names and managing network traffic. They fall into two primary categories.

DNS Message Categories:

• Query Messages: Sent by clients requesting domain-to-IP translations.
• Response Messages: Sent by DNS servers, providing the requested IP address or error details.

Understanding DNS structure is essential for networking interview questions. 

Also Read: Career in Web Development: Ultimate Guide

48. Why Is The POP3 Protocol Essential For Email Retrieval?

POP3 (Post Office Protocol v3) allows email clients like Outlook or Thunderbird to download messages from a mail server to a local device. It’s widely used where internet access is limited or storage is managed locally.

Key Features of POP3:

• Offline Access: Once downloaded, emails are available without needing an internet connection, ideal for mobile users or remote offices.
• Simple Protocol: Uses fewer server resources compared to IMAP, making it efficient for basic setups.
• One-Way Synchronization: By default, messages are removed from the server after download, reducing server load and storage needs.

POP3 is still used in lightweight email setups, and understanding it is common in networking interview questions and answers related to client-server protocols.

Also Read: What is the Difference Between Email and Gmail

49. How Would You Define Jitter In A Network, And What Effects Does It Have On Performance?

Jitter is the variation in packet arrival times over a network. It occurs when packets take different paths or experience inconsistent delays, even if sent at regular intervals.

Effects on Network Performance:

• Voice & Video Distortion: In VoIP calls (like Zoom or WhatsApp), jitter causes choppy audio or frozen video frames.
• Packet Loss: Excessive jitter can lead to out-of-order packets being dropped or discarded.
• Reduced Throughput: Routers and applications spend more time buffering or reordering packets, slowing down performance.

Jitter is a key metric in performance tuning questions and must be controlled in latency-sensitive environments like live streaming, online gaming, and real-time trading platforms.

Also Read: Data Visualisation: The What, The Why, and The How!

50. Why Is Bandwidth A Critical Factor In Overall Network Performance?

Bandwidth is the maximum rate at which data can be transmitted over a network. It directly affects how quickly users can upload, download, or stream content.

Importance of Bandwidth:

• Higher Throughput: More bandwidth enables faster data transfer, essential for cloud backups, file sharing, and video conferencing.
• Improved User Experience: Prevents buffering and lag in high-demand apps like Netflix, Zoom, or online games.
• Better Scalability: Supports more users and devices without compromising speed, especially in enterprise or campus networks.

In interviews, bandwidth is often discussed alongside latency and jitter when evaluating network performance and optimization strategies.

Also Read: What is Web Scraping & Why Use Web String?

51. How Can You Determine If An IP Address Is Private Or Public?

IP addresses are classified based on whether they are used within private networks or accessible over the internet. Knowing the difference is essential for network configuration and security.

Identification Methods:

• Private IP Ranges: Reserved for internal use and not routable on the public internet.
  • 10.0.0.0 to 10.255.255.255 (Class A)
  • 172.16.0.0 to 172.31.255.255 (Class B)
  • 192.168.0.0 to 192.168.255.255 (Class C)
• Public IP Verification: Use tools like whatismyip.com or ipinfo.io to check if an address is public and globally reachable.

Private IPs are used in homes, offices, and enterprise LANs, while public IPs are required for hosting websites or remote server access.

Also Read: IPV4 vs IPV6: Difference Between IPV4 and IPV6

52. Describe The Process Of Resolving A Domain Name To An IP Address.

DNS resolution is the process of translating a domain name (like www.google.com) into a machine-readable IP address (like 142.250.192.14). This enables devices to locate and connect to internet resources.

Resolution Process:

1. User Request: When you enter a URL, your browser sends a DNS query to the local DNS resolver, which is usually provided by your ISP or company network.
2. Recursive Query: The resolver contacts:
   • Root DNS Server directs to TLD (e.g., .com) servers.
   • TLD Server directs to the domain’s authoritative name server.

3. IP Retrieval: The authoritative server returns the correct IP address for the domain. The resolver caches it and sends it back to the browser.

   Understanding DNS resolution is essential for troubleshooting latency issues, configuring DNS records, and answering infrastructure-related networking interview questions and answers.

Also Read: Introduction to Docker Networking: Workflow, Networking Basics, Networking Commands

53. Which Diffie-Hellman Group Offers The Highest Level Of Security And Why?

Diffie-Hellman (DH) key exchange enables two parties to securely exchange cryptographic keys over an insecure channel. The strength of this exchange depends on the size and type of the DH group used.

Most Secure Diffie-Hellman Groups:

• Group 14+ (2048-bit and higher): Common in VPNs and TLS. Group 14 (2048-bit) is the minimum for secure enterprise use, while Group 21 and higher offer even stronger protection.
• Elliptic Curve DH (ECDH): Uses curves like Curve25519 to provide high security with shorter keys and faster computation, used in Signal and TLS 1.3.
• Post-Quantum DH (X25519/X448): Designed to resist quantum attacks. X25519 is widely adopted for forward secrecy in modern secure messaging apps.

Choosing stronger DH groups ensures encrypted traffic cannot be easily broken, even under future attack models. This is a common topic in advanced networking interview questions and answers on cryptography.

Also Read: Exploring Cryptography in Blockchain: Types and Key Algorithms

54. Explain How Flow Control Is Achieved In TCP.

Transmission Control Protocol (TCP) prevents network congestion by regulating data flow between sender and receiver.

Flow Control Mechanisms:

• Sliding Window Protocol: Adjusts window size based on network conditions.
• Acknowledgments (ACKs): Confirms received data before further transmission.
• Congestion Avoidance (TCP Reno/Tahoe): Slows down transmission during network congestion.

Effective flow control ensures optimal network performance, a key topic in networking interview questions. 

Also Read: Average Network Engineer Salary in India – For Freshers & Experienced in 2024

55. What Techniques Can Be Used To Determine An Active Port Number On A Network?

Identifying active ports helps network admins monitor services, detect vulnerabilities, and troubleshoot connectivity. Port scanning is the most common method.

Port Scanning Methods:

• SYN Scan (Half-Open Scan): Sends TCP SYN packets to check for responses. If a SYN-ACK is returned, the port is open. Used in tools like Nmap.
• UDP Scan: Sends UDP packets to identify services like DNS (port 53) or SNMP (port 161). Less reliable than TCP scans due to lack of acknowledgments.
• Tool-Based Detection:
  • Nmap: Scans a host or network to list open ports and running services.
  • Netstat: Shows active local ports and current network connections on Windows or Linux.

Port scanning is essential for penetration testing, firewall auditing, and security-focused networking interview questions and answers.

Also Read: What Is a System Administrator? Key Roles, Skills, and Career Insights for 2025

56. What Key Functions Does A Router Perform Within A Network?

A router directs network traffic by forwarding data packets between different networks.

Router Functions:

• Path Selection: Determines the best route for data transmission.
• Network Address Translation (NAT): Converts private IPs to public IPs for internet access.
• Security Filtering: Uses firewalls and ACLs to protect network traffic.

Routers are a fundamental topic in networking interview questions for professionals.

Also Read: What is Cybersecurity? Definition, Types, Career, Job Roles & Salary

57. How Does Network Address Translation (NAT) Work And What Are Its Benefits?

Network Address Translation (NAT) allows multiple devices on a private network to share a single public IP address.

NAT Benefits:

• IP Address Conservation: Reduces the need for IPv4 addresses.
• Security Enhancement: Hides internal IPs from external networks.
• Traffic Load Balancing: Distributes connections across multiple public IPs.

NAT is frequently covered in networking interview questions and answers on IP management. 

Also Read: AWS Vs Azure: Which Cloud Computing Platform is Right For You?

58. Explain The Purpose Of A Subnet Mask And Its Role In IP Addressing.

A subnet mask works with an IP address to determine which portion represents the network and which part identifies the host. It helps divide a large IP range into smaller, manageable subnetworks.

Subnet Mask Role:

• Network Identification: Masks out the network portion of an IP. For example, in 192.168.1.10/24, the subnet mask 255.255.255.0 identifies 192.168.1.0 as the network.
• IP Address Segmentation: Splits large networks into smaller subnets, for instance, isolating departments within a company.
• Enhanced Security and Performance: Reduces broadcast traffic and limits fault impact to individual subnets. Common in corporate LANs and cloud VPCs.

Understanding subnet masks is essential for routing, access control, and IP planning in networking interview questions and answers. 

59. Compare The Differences Between TCP And UDP In Terms Of Reliability And Speed.

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are key transport layer protocols, each with unique advantages.

Look at the difference between TCP and UDP:

This comparison is critical for networking interview questions and answers in protocol selection. 

Also Read: What Is Blockchain? How to Create Network,Code & It’s Architecture

60. What Are VLANs, And How Do They Improve Network Efficiency And Security?

A Virtual Local Area Network (VLAN) logically segments a physical network into multiple isolated networks, improving traffic management and reducing congestion.

VLAN Benefits:

• Traffic Segmentation: Limits broadcast traffic to specific VLANs, improving network performance.
• Improved Security: Isolates network segments, reducing unauthorized access risks. However, VLANs do not provide encryption or authentication—additional security measures like Access Control Lists (ACLs) and VLAN access control are necessary.
• Scalability: Enables flexible network segmentation without requiring new hardware.
• Simplified Management: Allows efficient grouping of devices based on function, department, or security needs.

VLANs are essential in enterprise networks, often appearing in networking interview questions for IT professionals.

These questions provide a strong foundation for IT professionals aiming for career growth in 2025.

To further strengthen your problem-solving and technical thinking, explore upGrad’s free Data Structures and Algorithms course. It covers key concepts like arrays, trees, stacks, and sorting techniques, essential for cracking tech interviews and building optimized network applications.

Top Strategies to Excel in Your Networking Interviews

To succeed in senior-level networking interviews, you need more than just textbook knowledge. Employers expect you to demonstrate hands-on experience with routing protocols like OSPF and BGP, deep understanding of firewalls and VPNs, and the ability to optimize performance under real-world constraints. 

You’ll also need to handle scenario-based questions involving load balancing, high availability, and cloud networking (AWS, Azure). The strategies below will help you tackle advanced networking interview questions and answers with confidence.

• Learn Advanced Networking Concepts: After understanding the basics, study BGP route summarization, confederations, and route reflectors, along with OSPF multi-area designs and MPLS Layer 3 VPNs. Learn how tools like Cisco NSO, Ansible, or Python scripts automate large-scale network changes. Senior interviews often include design-based questions or ask you to compare routing strategies for scalability and resilience.
• If you're new to scripting, start with this Free Python Course for Beginners to build the foundational skills needed to automate complex network tasks with ease.
• Strengthen Troubleshooting Skills: Practice using Wireshark, tcpdump, and SolarWinds to analyze real packet captures and identify issues like TCP retransmissions, asymmetric routing, or MTU mismatches. Be ready to walk through how you’d troubleshoot a high-latency issue across a hybrid cloud network or explain how you detected a Layer 2 loop using STP data.
• Stay Updated on Security Best Practices: Deepen your understanding of firewall rule creation, zero trust architectures, and intrusion detection tuning. Be familiar with IPsec tunnel configuration, SSL offloading, and VPN split tunneling.  Employers will ask about tools like Snort, Suricata, or how you handle DDoS threats at the edge using Cloudflare or AWS Shield. 
• Want to refresh your security fundamentals? Take this Free Cybersecurity Certification Course to learn the core principles that power real-world security strategies.
• Optimize Network Performance: Learn to configure QoS for VoIP, implement traffic shaping policies using Cisco QoS or Juniper CoS, and analyze bandwidth usage with NetFlow, sFlow, or IPFIX. Interviews often include case-based questions like optimizing performance for a video conferencing tool during peak traffic.
• Prepare for Hands-On Questions: Expect lab scenarios involving VLAN trunking issues, STP loop prevention, or EIGRP convergence optimization. Know how to configure router-on-a-stick, apply ACLs, and fine-tune routing protocols on the CLI in both Cisco and multi-vendor environments. Practical expertise is often tested via simulation or remote lab tasks.
• Review Real-World Case Studies: Study network outages such as the Facebook BGP misconfiguration in 2021 or Slack’s AWS Direct Connect failure. Understand what went wrong, how it was resolved, and what preventive steps could’ve been taken. These insights are valuable for answering behavioral or incident-response questions, which are common in senior networking interviews.

How Can upGrad Enhance Your Networking Capabilities?

If you're preparing for the networking interview questions and answers in 2025, you’ll need more than textbook theory. Employers expect you to explain BGP loop prevention, write automation scripts, troubleshoot with Wireshark, and optimize hybrid networks under real-world constraints.

But most IT professionals struggle because academic training skips real infrastructure challenges and enterprise tools. They understand protocols but not how to apply them under time pressure in multi-vendor environments. That’s where upGrad helps. 

With project-based learning, 1:1 mentorship, and expert-led classes, you’ll build hands-on skills tailored to actual industry use cases. We help you turn theory into job-ready performance. 

While we’ve highlighted several programs, here are a few more programs to sharpen your networking skills and accelerate your career path:

• Master of Design in User Experience
• Executive Programme in Generative AI for Leaders
• Master of Science in AI and Data Science, Jindal Global University
• Post Graduate in Product management Course from Duke CE
• DBA in Emerging Technologies with Concentration in Generative AI

If you're unsure which program fits your goals, upGrad offers free career counseling to guide your next move. You can also visit an upGrad center near you for personalized, in-person support.

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