Frequently Asked Interview Questions in Networking

If you’re preparing for a job in networking, first of all—good job! 🙌 Networking is the backbone of everything digital. Whether it’s the internet, a company's internal systems, or a cybersecurity setup—networking professionals make it all work.

In this blog, I’ll walk you through some of the most frequently asked networking interview questions, explain them in simple terms, and give you tips on how to answer confidently.

Let’s get started! 🚀

What is the difference between a switch, router, and hub?

✅ Simple Answer:

Hub: Sends data to all devices connected to it (not smart).
Switch: Sends data only to the intended device (smarter).
Router: Connects different networks together (e.g., your home to the internet).

🧠 Tip: Use a real-world example like “a router is like a post office that knows which city to send your letter to, while a switch is the mailman who knows which house to deliver to.”

What is an IP address?

✅ Simple Answer:

An IP address is a unique identifier for a device on a network—just like your home address.

🧠 Bonus Tip: Mention IPv4 (e.g., 192.168.1.1) vs IPv6 (newer version with longer format).

What’s the difference between TCP and UDP?

✅ Simple Answer:

TCP: Reliable, checks for errors, ensures data arrives in order (used in web browsing, email).
UDP: Faster but doesn’t guarantee delivery (used in video streaming, gaming).

🧠 Real Life Analogy: TCP is like sending a registered letter with confirmation. UDP is like shouting across the room—quick, but no guarantee it was heard correctly.

What is a subnet and why is it used?

✅ Simple Answer:

A subnet breaks a large network into smaller ones to improve performance and security.

🧠 Tip: You don’t need to calculate subnet masks unless asked—just show you understand the concept.

What is DNS and how does it work?

✅ Simple Answer:

DNS (Domain Name System) translates website names (like google.com) into IP addresses so computers can understand them.

🧠 Tip: Mention how it’s like a phonebook for the internet.

What is the OSI Model? Name its layers.

✅ Simple Answer:

The OSI model is a framework to understand how data travels through a network. It has 7 layers:

Physical
Data Link
Network
Transport
Session
Presentation
Application

🧠 Memory Tip: Use the mnemonic – Please Do Not Throw Sausage Pizza Away 🍕

What is NAT (Network Address Translation)?

✅ Simple Answer:

NAT allows multiple devices in a private network to access the internet using a single public IP address.

🧠 Real Life Example: Like a receptionist forwarding calls to the right employee inside the office.

What is DHCP and why is it important?

✅ Simple Answer:

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices in a network.

🧠 Tip: Say how it saves time and avoids conflicts in large networks.

Explain port numbers. What is port 80 or port 443?

✅ Simple Answer:

A port number identifies a specific process or service on a device.

Port 80: HTTP (unsecured web browsing)
Port 443: HTTPS (secured web browsing)

🧠 Extra Tip: Compare it to an apartment number in a building—it tells which door to knock on.

How do you troubleshoot a network issue?

✅ Simple Approach:

Check cables and connections (physical layer).
Ping devices to check connectivity.
Check IP configuration (ipconfig or ifconfig).
Check DNS resolution.
Restart network services.

🧠 Tip: Employers love a methodical approach. Show that you think step-by-step.

🎥 Learn Through Short Videos – Highly Recommended!

If you're someone who learns better by watching, here’s a fantastic YouTube playlist that explains many of these networking questions clearly and visually:

👉 Watch the video series here

These short videos are beginner-friendly and cover most key concepts that you’ll be asked in interviews. I highly recommend watching them after you read this blog—it will reinforce what you just learned!

What is the difference between circuit-switched and packet-switched communication?

Circuit-switched communication establishes a dedicated path between sender and receiver before the actual data transfer begins. It's like an old-school landline phone call 📞—once connected, the whole path stays reserved until the call ends.

Packet-switched communication, used in the internet 🌐, breaks data into smaller packets and sends them independently. These packets can take different routes and are reassembled at the destination. It’s faster, more flexible, and makes better use of network resources.

💡 Tip: The interviewer expects you to explain the concept with a real-world analogy, like comparing phone calls vs. internet data.

Define latency and bandwidth. How do they affect network performance?

Latency is the delay between sending a request and getting a response, measured in milliseconds ⏱️. It matters most in real-time communication, like gaming 🎮 or video calls 📹. Lower latency = faster response.

Bandwidth is the maximum data that can be transferred per second, usually in Mbps or Gbps 📶. More bandwidth means smoother streaming 🎥, faster downloads, and better multitasking on the network.

💡 Tip: Keep it simple. Emphasize how latency = delay and bandwidth = capacity. Use relatable examples.

What are the basic components involved in a communication system?

A communication system has the following parts:

Sender 🧑‍💻: Generates the message
Transmitter 📡: Converts the message into signals
Transmission medium 📶: The path (like cables or air) through which signals travel
Receiver 📥: Captures the signal
Destination 🧑‍🏫: Interprets and uses the message

These components work together to deliver information from one end to the other.

💡 Tip: Don't just list terms—briefly explain each in one line. It shows you understand how data moves in a system.

What are some key differences between PSTN and VoIP?

PSTN (Public Switched Telephone Network) is the traditional system using circuit switching. It's reliable 📞 but not very flexible or cost-effective for long-distance calls.

VoIP (Voice over IP) converts voice into data packets and sends it over the internet 🌐. It's cheaper 💰, supports features like video conferencing 📹, and is widely used in modern communication apps.

💡 Tip: Interviewers want you to know both systems. Highlight cost, flexibility, and technology used.

List three types of wired communication media and compare their performance.

Here are three commonly used wired media:

Twisted-pair cable 🧵: Cheap, easy to install, used in LANs—but limited in speed and distance
Coaxial cable 📺: Better shielding, supports higher speeds, used in cable internet and TV
Fiber optic cable 💡: Uses light for transmission, extremely fast and secure, ideal for long-distance and high-speed data

💡 Tip: When comparing, focus on cost, speed, and range. That’s what interviewers look for in performance comparisons.

What is Optical Fiber Communication (OFC)? Name one advantage over copper cables.

Optical Fiber Communication (OFC) uses light signals to transmit data through very thin strands of glass or plastic 💡. It's one of the fastest and most reliable methods for data transfer over long distances.

One major advantage over copper cables is speed and distance—fiber can carry data much faster and over much longer ranges without signal loss 🚀.

💡 Tip: Keep it focused—mention light-based transmission and give one clear advantage like speed, range, or immunity to interference.

Compare twisted-pair cable, coaxial cable, and fiber optics in terms of cost and speed.

Twisted-pair cable 🧵: Cheapest option, easy to install, commonly used in LANs—but lower speed and more interference-prone
Coaxial cable 📺: Moderate cost, better shielding than twisted pair, suitable for cable internet and TV
Fiber optics 💡: Highest cost but unmatched speed and reliability—ideal for high-performance networks

💡 Tip: Interviewers want you to organize your comparison clearly—structure your answer around both cost and speed, and mention typical use-cases.

What is the difference between licensed and unlicensed wireless spectrum?

A licensed spectrum is assigned by government authorities to organizations or service providers 📡. It offers exclusive use, less interference, and is used in cellular networks like LTE 📱.

An unlicensed spectrum is free for public use, such as Wi-Fi or Bluetooth 🌐. It’s more flexible but prone to interference because multiple devices can operate on the same frequency.

💡 Tip: Keep the focus on who can use it and how interference is managed. Use Wi-Fi vs. LTE as an example.

Give two examples of unlicensed frequency bands commonly used in home networking.

Two commonly used unlicensed bands are:

2.4 GHz 🌐: Wider range, but more interference (used by many devices like microwaves, Bluetooth, etc.)
5 GHz ⚡: Faster and less crowded, but has a shorter range

These are mainly used in Wi-Fi routers for home and office networking.

💡 Tip: Just name the two bands and mention range vs. speed trade-offs. Short and to the point.

Explain one use-case each for Wi-Fi, LTE, and Zigbee.

Wi-Fi 🌐: Ideal for high-speed internet access at home or in public areas—great for browsing, video calls, and streaming
LTE 📱: Used in mobile networks for data access on smartphones and tablets when Wi-Fi isn’t available
Zigbee 🔌: Low-power, short-range communication used in smart home devices like sensors, lights, or door locks

💡 Tip: Give a real-world example for each. Interviewers love answers that connect technology to daily life.

Define network topology and list any four types.

Network topology refers to the layout or structure of how devices (nodes) are connected in a network 🔁. It defines how data flows and how devices interact.

Four common types are:

Bus topology: All devices connected to a single central cable
Star topology: Devices connected through a central hub or switch
Ring topology: Each device connected to two others, forming a ring 🔄
Mesh topology: Every device connected to every other device for full redundancy

💡 Tip: Be ready to define the term and name four types clearly. Bonus if you can describe each briefly.

Which topology is most fault-tolerant and why?

Mesh topology is the most fault-tolerant because each device is connected to every other device 🔀. If one link fails, data can still travel through other paths. This ensures high reliability and no single point of failure.

💡 Tip: Highlight the redundancy feature and use the phrase “no single point of failure”—interviewers love hearing that.

In which scenarios would a mesh topology be ideal?

Mesh topology is ideal in critical systems where high availability and fault tolerance are essential—such as military networks, smart grids, or data centers 🖥️.

Even if some connections break, the network continues to operate without interruption, making it suitable for mission-critical environments.

💡 Tip: Don’t just repeat “it’s fault-tolerant”—give real-life examples like smart cities or disaster recovery setups.

List the 7 layers of the OSI model and their primary functions.

Here are the 7 layers from top to bottom:

Application 🎯 – Interface for end-user apps like browsers and email
Presentation 🎨 – Translates data formats (e.g., encryption, compression)
Session 🗂️ – Manages sessions and connections between devices
Transport 🚚 – Ensures reliable data delivery (TCP/UDP)
Network 🛰️ – Handles routing and logical addressing (IP)
Data Link 🔗 – Deals with MAC addresses and switches
Physical ⚙️ – Transmits raw bits via cables or radio waves

💡 Tip: Use a mnemonic like “All People Seem To Need Data Processing” to recall the order quickly.

Which layer in the OSI model is responsible for encryption and decryption?

The Presentation layer (Layer 6) is responsible for data encryption and decryption 🔐. It ensures that the data is formatted correctly for the application layer and handles functions like compression and translation between formats.

💡 Tip: Clearly mention Layer 6 and the words “encryption/decryption” to show you’ve memorized the OSI functions with understanding.

Compare OSI and TCP/IP models in terms of structure and real-world usage.

The OSI model has 7 layers and is a theoretical framework used mainly for teaching and understanding networking concepts 🏫.

The TCP/IP model has 4 layers and is practical—used in real-world internet communication 🌍. It combines some OSI layers but covers everything needed for actual data transmission.

💡 Tip: Emphasize that OSI is a learning tool, TCP/IP is practical. Use terms like “theoretical vs. practical” to show insight.

At which OSI layer do switches and routers operate?

Switches work at the Data Link layer (Layer 2) 🔗, using MAC addresses to forward data within a LAN.

Routers operate at the Network layer (Layer 3) 🛰️, directing data between different networks using IP addresses.

💡 Tip: Name the layers clearly and associate each device with its key addressing method (MAC for switches, IP for routers).

What is the role of the TCP protocol versus UDP?

TCP (Transmission Control Protocol) 🚚 ensures reliable, ordered, and error-checked delivery of data—great for things like web pages and emails.

UDP (User Datagram Protocol) ⚡ is faster but does not guarantee delivery or order—used for streaming or gaming where speed matters more than perfect accuracy.

💡 Tip: Contrast reliability vs. speed clearly. Mention typical applications for each to sound confident.

Identify which layers the following protocols belong to: HTTP, DNS, IP, ARP.

HTTP – Application layer 🌐
DNS – Application layer 🔍
IP – Network layer 🛰️
ARP – Data Link layer 🔗

💡 Tip: Group application protocols together, and remember that IP is network, ARP is data link.

Explain how DNS works and which layer it belongs to.

DNS (Domain Name System) translates human-friendly domain names (like google.com) into IP addresses needed for routing 🌍. It acts like the internet’s phonebook.

DNS operates at the Application layer because it provides services directly to user applications like browsers.

💡 Tip: Use the “phonebook” analogy. Make sure to say DNS is at the Application layer to show understanding of protocol layering.

What happens during the three-way handshake in TCP?

The three-way handshake establishes a reliable connection between two devices before data transfer:

The client sends a SYN (synchronize) packet to the server ✋
The server replies with a SYN-ACK (synchronize-acknowledge) 🤝
The client responds with an ACK (acknowledge) ✅

Once this handshake completes, data can be sent securely and reliably.

💡 Tip: Focus on the three steps and their purpose—to set up a reliable, synchronized connection.

Differentiate between a hub, a switch, and a router.

Hub: Basic device that broadcasts incoming data to all ports—no intelligence 🤷‍♂️
Switch: Smart device that forwards data only to the intended device using MAC addresses 🔗
Router: Connects different networks and routes data between them using IP addresses 🌐

💡 Tip: Highlight the increasing “smartness” and purpose: broadcast → switch → route.

What is the role of a Network Interface Card (NIC)?

A NIC is hardware inside a device that connects it to the network 🌐. It handles sending and receiving data packets at the physical and data link layers.

Think of it as the network adapter that lets your computer “talk” to other devices.

💡 Tip: Keep it simple and mention it’s a hardware component responsible for network connectivity.

At what OSI layer does a firewall typically operate?

Firewalls can operate at multiple layers, but they mostly work at the Network layer (Layer 3) 🛡️ and Transport layer (Layer 4), filtering packets based on IP addresses, ports, and protocols to protect networks.

Some advanced firewalls operate at higher layers for deeper inspection.

💡 Tip: Mention Layers 3 and 4 primarily, showing awareness of packet filtering and security.

What is MAC address and how is it different from an IP address?

A MAC address is a unique hardware identifier assigned to a network interface card 🏷️, used for local network communication.

An IP address is a logical address assigned to devices for identifying them on larger networks or the internet 🌍.

MAC addresses don’t change, but IP addresses can change depending on the network.

💡 Tip: Compare hardware vs. logical addressing, and fixed vs. dynamic nature clearly.

What is the role of a load balancer in a network setup?

A load balancer distributes incoming network traffic across multiple servers ⚖️. This helps ensure no single server gets overwhelmed, improving performance, reliability, and availability of applications or websites.

Think of it like a traffic cop directing cars to different lanes to avoid congestion.

💡 Tip: Use simple analogies and emphasize distribution and reliability to show understanding.

How does a proxy server differ from a gateway?

A proxy server acts as an intermediary between clients and the internet 🌐, forwarding requests and often providing anonymity, caching, or filtering.

A gateway connects two different networks that use different protocols, translating and routing traffic between them 🔄.

💡 Tip: Highlight the proxy’s role in client requests and the gateway’s role in connecting different networks.

What is the purpose of an IP address in a network?

An IP address uniquely identifies a device on a network, enabling devices to find and communicate with each other over the internet or local networks 🆔.

Without IP addresses, data wouldn’t know where to go.

💡 Tip: Keep it simple but clear—“unique identifier” and “enables communication” are key phrases.

Define subnet mask and explain its use.

A subnet mask divides an IP address into the network and host portions 🛠️. It helps devices determine whether a destination is within the same network or if the data needs to be routed elsewhere.

Think of it as a guide that tells your device how to reach others on the network.

💡 Tip: Explain both the network/host division and its role in routing decisions.

Convert the subnet mask 255.255.255.0 into CIDR notation.

The subnet mask 255.255.255.0 corresponds to /24 in CIDR notation.

This means the first 24 bits of the IP address are the network part, and the remaining 8 bits are for hosts.

💡 Tip: Remember to count the number of 1s in the subnet mask’s binary form; here, it’s 24 bits.

What is the difference between private and public IP addresses?

Private IP addresses are used inside local networks and aren’t routable on the internet 🏠. Examples include 192.168.x.x or 10.x.x.x.

Public IP addresses are assigned by ISPs and are unique on the internet 🌐, allowing devices to communicate globally.

💡 Tip: Focus on where each is used and the fact that private IPs are hidden behind routers/firewalls.

What is the loopback IP address and what is it used for?

The loopback IP address is 127.0.0.1 and it’s used by a device to test its own network stack 🖥️. It sends traffic back to itself without leaving the device.

It helps troubleshoot network software without needing a real network connection.

💡 Tip: Mention “testing internal network” and that it never goes outside the device.

What problem does IPv6 solve compared to IPv4?

IPv6 solves the problem of IPv4 address exhaustion by providing a much larger address space—128 bits instead of 32 bits 🌍.

It also improves routing efficiency and security features.

💡 Tip: Highlight the huge increase in address space and briefly mention improved features.

Write a valid example of an IPv6 address.

A valid IPv6 address example:
2001:0db8:85a3:0000:0000:8a2e:0370:7334

It uses hexadecimal digits separated by colons.

💡 Tip: Show familiarity with IPv6 format and mention use of hex and colons.

What is routing in the context of computer networks?

Routing is the process of selecting paths for data packets to travel from source to destination across interconnected networks 🚦.

Routers use routing tables and protocols to make these decisions.

💡 Tip: Explain routing as “path selection” and mention routers and routing tables.

Explain the difference between static and dynamic routing.

Static routing is when network routes are manually configured by an admin 📝. It’s simple but doesn’t adapt to network changes automatically.

Dynamic routing uses protocols that automatically discover and update routes based on current network conditions 🔄, making networks more flexible and resilient.

💡 Tip: Emphasize manual setup vs. automatic adaptability, showing you understand pros and cons.

Name two dynamic routing protocols and their primary features.

OSPF (Open Shortest Path First): Uses link-state info, fast convergence, and scales well in large networks 🚀.
RIP (Routing Information Protocol): Simpler, uses hop count as metric, good for smaller networks 🐢.

💡 Tip: Mention the key feature of each and where they’re typically used.

How does a router decide the best path for a packet?

Routers use routing tables and metrics (like hop count, bandwidth, delay) to evaluate and choose the most efficient path for data packets 🛤️.

Protocols like OSPF or BGP help routers share info to update these tables.

💡 Tip: Focus on routing tables and metrics, showing awareness of dynamic decision-making.

You are tasked with setting up a small office network. What devices and topology would you choose, and why?

For a small office, I’d use a switch to connect devices efficiently and a router for internet access 🌐. A star topology is ideal because it’s easy to manage and troubleshoot, with all devices connected to a central switch.

This setup balances performance, cost, and scalability.

💡 Tip: Explain device roles and justify topology choice clearly and practically.

If two devices in the same subnet cannot communicate, what are the possible reasons?

Possible reasons include:

Incorrect subnet masks causing misidentification of the network 📛
Firewall or security settings blocking traffic 🚫
Faulty cables or hardware issues 🔌
IP address conflicts or misconfiguration ⚠️

💡 Tip: Show you think about addressing, security, and physical layer problems.

Final Thoughts 💡

Interviews are not just about technical knowledge—they’re about clear thinking and communication. When you explain things simply, it shows you really understand them.

Keep practicing, build mini labs at home (you can use tools like Cisco Packet Tracer or GNS3), and stay confident. You've got this! 💪

If you want more interview Q&As or topic-specific blogs (like firewalls, VPNs, or cybersecurity networking), just let me know. I’d love to help you prepare!

🖐 Got a question? Drop it in the comments below or shoot me a message. Happy learning and good luck with your interviews! 🚀