Dear friends, are you preparing for a computer network interview? In this article, I cover 50 important questions and answers in simple language. Each answer includes real-life examples to help you understand concepts easily. Whether you are a beginner or an experienced candidate, this article will help you crack your interview confidently.
1. What is a computer network?
A computer network is when two or more computers are connected to share information, files, or the internet. It can be wired or wireless.
Example:
Imagine students in a classroom sharing notes by passing them around. That’s like a network where computers share data with each other.
2. What are the types of networks?
There are mainly three types: LAN (small area like home or office), MAN (medium area like a city), and WAN (large area like internet).
Example:
Your home Wi-Fi is a LAN, your city’s cable network is a MAN, and when you use Facebook or Google, that’s WAN.
3. What is an IP address?
An IP address is like the home address of your computer on the internet. Every device has one.
Example:
Just like a postman needs your house number to deliver letters, websites need your IP address to send you videos, games, or messages correctly.
4. What is DNS?
DNS means Domain Name System. It changes website names into numbers (IP addresses) that computers understand.
Example:
Instead of remembering your friend’s phone number, you save their name in contacts. Similarly, DNS lets you type google.com instead of a long number like 142.250.190.14.
5. What is the difference between HTTP and HTTPS?
HTTP is a way computers share information but it’s not safe. HTTPS is safer because it locks the information using encryption.
Example:
HTTP is like writing on a postcard that anyone can read, while HTTPS is like putting your message inside a sealed envelope so only the receiver opens it.
6. What is a router?
A router is a device that connects different networks together and sends information to the correct place.
Example:
Think of a router like a traffic policeman who directs cars on the right road so they reach the right destination.
7. What is a switch?
A switch connects many devices in the same network and makes sure data reaches only the correct device.
Example:
Like a teacher calling only one student’s name instead of shouting to the whole class. This saves time and avoids confusion.
Table: Difference between Switch and Hub
| Feature | Switch | Hub |
|---|---|---|
| Sends Data To | Correct device only | All devices |
| Speed | Faster | Slower |
| Security | Safer | Less safe |
8. What is a hub?
A hub is a device that connects many computers, but it sends data to all devices instead of just one.
Example:
Like shouting loudly in a room where everyone hears, even if the message is meant for only one person.
9. What is a MAC address?
A MAC address is a special ID number for every device’s network card. No two devices have the same.
Example:
Like fingerprints, every person has a different one. Similarly, your laptop and phone have different MAC addresses to identify them.
10. What is a firewall?
A firewall is like a guard that protects computers from harmful data or hackers by checking what enters or leaves the network.
Example:
Like a school gatekeeper checking every visitor before they enter the school to keep students safe.
11. What is bandwidth?
Bandwidth is the maximum amount of data that can pass through a network in one second.
Example:
Imagine a water pipe. A bigger pipe lets more water flow, just like higher bandwidth lets more videos, songs, or files move faster on the internet.
12. What is latency?
Latency is the time delay between sending data and receiving it back.
Example:
Like shouting to your friend across a valley and waiting for the echo to return. The longer it takes, the higher the latency in the network.
13. What is VPN?
VPN means Virtual Private Network. It hides your online activities and makes your connection safe.
Example:
Like wearing sunglasses and a hoodie in public so no one recognizes you, a VPN hides your real IP address from others on the internet.
14. What is topology in networks?
Topology is the way computers are arranged and connected in a network. Common types are star, bus, ring, and mesh.
Example:
Think of classroom seating. Some sit in rows (bus), some in circles (ring), and some around one teacher (star).
Table: Types of Network Topology
| Topology | Shape Example | Use Case |
|---|---|---|
| Star | Computers connected to one central hub | Office networks |
| Bus | Single line connection | Small labs |
| Ring | Devices in a circle | Old LAN setups |
| Mesh | Each device connects to all | Big networks |
15. What is a packet?
Data in a network is broken into small pieces called packets before sending. Each packet travels separately and re-joins at the end.
Example:
Like a big pizza cut into slices. Instead of carrying the whole pizza, slices are shared and then joined back together.
16. What is TCP/IP?
TCP/IP is a set of rules that computers use to talk to each other on the internet. TCP makes sure data is delivered correctly, while IP decides the address.
Example:
Like a delivery service—TCP checks the package, IP finds the house.
17. What is the difference between TCP and UDP?
TCP is reliable but slower. UDP is faster but less reliable.
Example:
TCP is like sending a registered parcel that needs a signature. UDP is like dropping a postcard into a mailbox without checking if it arrived.
Table: TCP vs UDP
| Feature | TCP (Reliable) | UDP (Fast) |
|---|---|---|
| Speed | Slower | Faster |
| Reliability | Guaranteed delivery | Not guaranteed |
| Example | Email, Web browsing | Online games, Videos |
18. What is a protocol?
A protocol is a set of rules for communication between computers. Without protocols, devices wouldn’t understand each other.
Example:
Like traffic rules, everyone must follow them to avoid accidents. Similarly, protocols keep data moving smoothly on the internet.
19. What is DHCP?
DHCP stands for Dynamic Host Configuration Protocol. It gives devices an IP address automatically when they join a network.
Example:
Like a teacher assigning roll numbers to students so they can be easily identified in class.
20. What is a gateway?
A gateway connects two different networks and helps them communicate.
Example:
Like a translator who knows two languages and helps two people talk, a gateway helps two different types of networks share data.
21. What is a subnet mask?
A subnet mask divides an IP address into network and host parts. It helps identify which devices are inside the same network.
Example:
Like dividing a classroom into groups of students, so each group is easy to recognize.
22. What is ARP?
ARP stands for Address Resolution Protocol. It finds the MAC address of a device when you only know its IP address.
Example:
Like knowing your friend’s name (IP) but asking others for their phone number (MAC) to call them.
23. What is ping?
Ping is a command used to check if a computer can connect to another computer on a network.
Example:
Like shouting “Are you there?” and waiting for your friend to reply “Yes!” It shows if the connection works.
24. What is bandwidth vs throughput?
Bandwidth is the maximum possible data transfer. Throughput is the actual data transfer speed.
Example:
A road may allow 100 cars per hour (bandwidth), but due to traffic only 70 cars pass (throughput).
Table: Bandwidth vs Throughput
| Feature | Bandwidth (Capacity) | Throughput (Actual) |
|---|---|---|
| Meaning | Maximum possible speed | Real speed achieved |
| Example | 100 Mbps internet plan | 70 Mbps download |
25. What is a proxy server?
A proxy server is a middle computer between you and the internet. It hides your identity and can block unwanted sites.
Example:
Like asking a friend to buy something from a shop so your name stays secret.
26. What is ICMP?
ICMP means Internet Control Message Protocol. It is used by devices to send error messages or test communication.
Example:
When you use the “ping” command, ICMP is the language computers use to say, “Yes, I’m here!” or “No, I can’t be reached.”
27. What is the difference between static and dynamic IP?
- Static IP: Fixed and doesn’t change.
- Dynamic IP: Changes each time you connect.
- Example:
- A static IP is like your permanent home address. A dynamic IP is like a hotel room number that changes when you check in again.
Table: Static vs Dynamic IP
| Type | Static IP | Dynamic IP |
|---|---|---|
| Changes | Never | Changes often |
| Cost | More expensive | Cheaper |
| Example | Business server | Home Wi-Fi |
28. What is NAT?
NAT means Network Address Translation. It lets many devices share one public IP address on the internet.
Example:
Like a family using one house address for all members, even though each person has their own room number inside.
29. What is a VLAN?
VLAN means Virtual Local Area Network. It divides a physical network into smaller, safer virtual groups.
Example:
In a school, you separate students into classes even though they are in the same building. VLAN separates computers in a similar way.
30. What is a port number?
A port number helps computers know which application data belongs to.
Example:
A house address gets you to the house, but the flat number takes you to the right room. Similarly, port numbers guide data to the correct program.
31. What is FTP?
FTP means File Transfer Protocol. It is used to move files between computers on a network.
Example:
Like carrying homework in a pen drive between two friends, FTP moves files from one computer to another through the internet.
32. What is SMTP?
SMTP means Simple Mail Transfer Protocol. It is used for sending emails.
Example:
When you send a message through Gmail, SMTP is the postman that delivers your email safely to the receiver’s inbox.
33. What is POP3 and IMAP?
Both are used for receiving emails. POP3 downloads emails to your computer, while IMAP keeps them on the server and syncs across devices.
Example:
POP3 is like taking books home from a library. IMAP is like reading books inside the library whenever you want.
34. What is the OSI model?
The OSI model explains how data travels in 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Example:
Like a letter going through steps — writing, sealing, sending, traveling, receiving, opening, and reading. Each step is like one OSI layer.
Table: OSI 7 Layers
| Layer No. | Layer Name | Example Activity |
|---|---|---|
| 7 | Application | Web browsing, Email |
| 6 | Presentation | Data translation |
| 5 | Session | Maintaining connection |
| 4 | Transport | Splitting data packets |
| 3 | Network | IP addressing |
| 2 | Data Link | MAC addressing |
| 1 | Physical | Cables, Wi-Fi signals |
35. What is the difference between OSI and TCP/IP model?
OSI has 7 layers, while TCP/IP has 4 layers. Both explain how data travels.
Example:
OSI is like a detailed recipe with many steps, TCP/IP is like a shorter recipe with fewer steps but still makes the same dish.
36. What is a VPN (Virtual Private Network)?
A VPN works like a secret tunnel on the internet. It hides your real location and protects your data while browsing. For example, if you are using Wi-Fi at a café, a VPN makes sure hackers cannot see your personal details, just like curtains protect your privacy at home.
Table Example – VPN Uses
| Use Case | Example | Benefit |
|---|---|---|
| Secure Browsing | Public Wi-Fi in airports | Data protection |
| Watching Content | Netflix USA from India | Access geo-blocked sites |
| Online Shopping | Shopping apps/websites | Safer transactions |
37. What is a Proxy Server?
A proxy server acts like a middleman between you and the internet. When you search something, it first goes to the proxy, then to the website. This keeps your identity hidden. For example, schools often use proxy servers to block social media sites during study time.
38. What is a Router?
A router is like a traffic police officer for your internet. It directs data from your internet line to the right devices at home. For example, when you stream YouTube on your phone while someone plays games on a PC, the router manages both without mixing signals.
Table Example – Router vs Switch
| Feature | Router | Switch |
|---|---|---|
| Role | Connects devices to the internet | Connects devices inside network |
| Example Use | Wi-Fi at home | Office computer connections |
39. What is a Switch?
A switch connects many devices in a local area, like in an office or school. It decides where data should go, so computers don’t get confused. For example, if 10 students send files at once, the switch ensures each file reaches the correct computer without traffic jams.
40. What is a Gateway?
A gateway is like a bridge that connects two different networks. It makes sure devices speaking different “languages” can still communicate. For example, when your office uses one type of system and your client uses another, the gateway helps them share data smoothly, just like a translator between two people.
41. What is Cloud Computing in Networking?
Cloud computing means storing and accessing data over the internet instead of on your computer. For example, when you use Google Drive to save homework, you’re using the cloud. It helps people share files easily, access them from anywhere, and saves space on personal computers or phones.
📌 Table Example – Cloud Services
| Service Type | Example | Use Case |
|---|---|---|
| Storage | Google Drive | Save and share documents |
| Computing Power | AWS, Azure | Run apps on internet servers |
| Backup | iCloud | Save phone photos automatically |
42. What is NAT (Network Address Translation)?
NAT allows multiple devices in a private network to share one public IP address on the internet. For example, at home, your laptop, phone, and smart TV all use one public IP provided by your ISP, but NAT makes sure each device’s data is sent correctly.
43. What is a VLAN (Virtual LAN)?
A VLAN is a virtual network inside a bigger network. It separates devices into smaller groups for security and efficiency. For example, in an office, HR computers may be on one VLAN, and finance computers on another, even though all are connected to the same network.
44. What is a Port Number?
A port number tells a computer which program should receive the incoming data. For example, when you browse a website, port 80 is used for HTTP, and port 443 is for HTTPS. It’s like sending a letter to a house and adding the flat number for the right room.
45. What is FTP (File Transfer Protocol)?
FTP is used to transfer files between computers over a network. For example, a website designer uploads images to a server using FTP. It’s like using a delivery service to send your files from your house to someone else safely.
46. What is SMTP (Simple Mail Transfer Protocol)?
SMTP is the method used to send emails from your computer to a mail server. For example, when you send a Gmail message, SMTP acts like a postal worker delivering your email to the receiver’s inbox securely and reliably.
47. What is POP3 and IMAP?
Both are ways to receive emails. POP3 downloads emails to your device, IMAP keeps emails on the server and syncs across devices. For example, POP3 is like taking books home, IMAP is like reading books in the library whenever you want.
48. What is ICMP (Internet Control Message Protocol)?
ICMP sends messages about network problems or checks connections. For example, the “ping” command uses ICMP to ask another computer, “Are you there?” and get a reply. It’s like sending a test message to see if your friend is online.
49. What is Latency vs Bandwidth?
Bandwidth is how much data can move at once, latency is how fast it travels. For example, a wide road (high bandwidth) allows more cars, but traffic jams (high latency) slow cars down. Both affect internet speed and online experiences like gaming or video calls.
📌 Table Example – Bandwidth vs Latency
| Feature | Bandwidth | Latency |
|---|---|---|
| Meaning | Max data capacity | Delay in data transfer |
| Example | 100 Mbps internet plan | Time to respond to ping |
50. What is a Proxy Server?
A proxy server is a middle computer between your device and the internet. It hides your IP, filters content, or improves speed. For example, schools use proxies to block social media while still letting students browse educational sites safely.
51. What is Mesh Topology?
In mesh topology, every device connects to every other device in a network. It’s very reliable because if one link fails, others can carry data. For example, in an office, even if one cable breaks, computers can still send emails using another path.
