1. What is a "Computer Network"?

A collection of interconnected computers and other devices that communicate with each other to share data, resources, and services.

2. What are the key components of a Network?

Nodes: Computers, servers, or devices.
Links: Wired (fiber, copper) or wireless (Wi-Fi, satellite) transmission media.
Protocols: Rules for communication (e.g., TCP/IP, HTTP).
Network Interface Card (NIC): Hardware that allows a computer to connect to a network.

3. What is the "OSI Model"?

The Open Systems Interconnection model is a conceptual framework that describes how data is transmitted over a network across 7 distinct layers.

4. Name the 7 Layers of the OSI Model?

Physical Layer: Hardware, bits.
Data Link Layer: Framing, error detection (MAC addresses).
Network Layer: Routing, IP addressing (Packets).
Transport Layer: Reliability, segmentation (TCP/UDP).
Session Layer: Maintaining connections.
Presentation Layer: Encryption, compression, data formatting.
Application Layer: User interaction (HTTP, FTP, SMTP).

5. What is the "TCP/IP Model"?

A simpler model used in the internet that has 4 layers: Network Access, Internet, Transport, and Application.

6. What is the difference between "Hub", "Switch", and "Router"?

Hub: Broadcasts data to all ports (dumb device).
Switch: Sends data only to the specific destination port using MAC addresses (intelligent).
Router: Connects different networks and routes data using IP addresses.

7. What is an "IP Address"?

A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.

8. What's the difference between "IPv4" and "IPv6"?

IPv4: 32-bit; 4 billion addresses; decimal format (e.g., 192.168.1.1).
IPv6: 128-bit; nearly infinite addresses; hexadecimal format.

9. What is "MAC Address"?

Media Access Control address. A unique 48-bit identifier assigned to a network interface controller (NIC) by the manufacturer. It's a permanent physical address.

10. What is "TCP" (Transmission Control Protocol)?

A connection-oriented protocol that ensures reliable, ordered, and error-checked delivery of data between applications.

11. What is "UDP" (User Datagram Protocol)?

A connectionless, lightweight protocol that provides fast data transmission but doesn't guarantee reliability or ordering (used for streaming/gaming).

12. What is "DNS" (Domain Name System)?

A hierarchical decentralized naming system that translates human-readable domain names (e.g., google.com) into IP addresses.

13. What is "HTTP" vs "HTTPS"?

HTTP: Hypertext Transfer Protocol; unencrypted data.
HTTPS: Hypertext Transfer Protocol Secure; uses SSL/TLS for encryption.

14. What is "DHCP" (Dynamic Host Configuration Protocol)?

A protocol that automatically assigns dynamic IP addresses and other network configurations to devices on a network.

15. What is "ARP" (Address Resolution Protocol)?

A protocol used to find the MAC address of a device when its IP address is known.

16. What is "ICMP" (Internet Control Message Protocol)?

A protocol used by network devices to send error messages and operational information (e.g., for ping and traceroute).

17. What is a "Subnet"?

A sub-portion of a larger network. Subnetting is the process of dividing a network into smaller, more manageable pieces to improve performance and security.

18. What is "Default Gateway"?

The IP address of the router that a host uses to send data to destinations outside its local network.

19. What is "NAT" (Network Address Translation)?

A process that allows multiple devices in a private network to share a single public IP address to access the internet.

20. What is a "Firewall"?

A network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules.

21. What is a "VPN" (Virtual Private Network)?

An encrypted tunnel that allows a user to securely access a private network over a public network (like the internet).

22. What is the difference between "Bandwidth" and "Latency"?

Bandwidth: The maximum rate of data transfer across a network path.
Latency: The time it takes for a data packet to travel from source to destination.

23. What is "Jitter"?

The variation in the time between data packets arriving at their destination, caused by network congestion or route changes.

24. What is "CSMA/CD" and "CSMA/CA"?

CSMA/CD (Collision Detection): Used in Ethernet to manage collisions.
CSMA/CA (Collision Avoidance): Used in Wi-Fi to prevent collisions.

25. What is "Three-Way Handshake"?

The process used by TCP to establish a connection:

SYN: Client sends a synchronization request.
SYN-ACK: Server acknowledges and sends its own request.
ACK: Client acknowledges the server's request.

26. What is "FTP" (File Transfer Protocol)?

A standard protocol for transferring files between a client and a server on a computer network.

27. What is "SMTP", "POP3", and "IMAP"?

SMTP: For sending emails.
POP3: For downloading emails (usually deletes from server).
IMAP: For syncing emails (keeps them on server).

28. What is the "BGP" (Border Gateway Protocol)?

The protocol used to exchange routing information between different Autonomous Systems (AS) on the internet.

29. What is "Socket" in Networking?

An endpoint in a two-way communication link between two programs running on the network. It's a combination of an IP address and a Port number.

30. What is "Port"?

A logical point of connection in an OS used to identify a specific process or service (e.g., HTTP = 80, HTTPS = 443, SSH = 22).

31. What is "Proxy Server"?

A go-between for a client and another server. It can provide caching, anonymity, and security.

32. What is "SSL/TLS"?

Cryptographic protocols designed to provide secure communication over a network by encrypting data.

33. What is "Network Topology"?

The physical or logical arrangement of nodes and links in a network (e.g., Bus, Star, Ring, Mesh, Tree).

34. What is "Star Topology"?

Nodes are connected to a central hub or switch. If the hub fails, the network fails, but if a single cable fails, only that node goes down.

35. What is "Mesh Topology"?

Every node is connected to every other node, providing high redundancy but very high cabling cost.

36. What is "Collision Domain"?

A network segment where data packets can collide with one another when sent on a shared medium (e.g., hubs create large collision domains).

37. What is "Broadcast Domain"?

A logical part of a network where a broadcast message is received by all nodes (e.g., routers break broadcast domains).

38. What is "NFS" (Network File System)?

A protocol that allows a user on a client computer to access files over a network similar to how local storage is accessed.

39. What is "SSH" (Secure Shell)?

A cryptographic network protocol used for secure login and data communication between computers over an unsecure network.

40. What is "Telnet"?

An older, unsecure protocol for remote terminal access. Everything is sent in plain text.

41. What is "Ping"?

A utility used to test the reachability of a host on an IP network and measure round-trip time.

42. What is "Traceroute"?

A utility that shows the path (hops) that a packet takes from source to destination.

43. What is the "Application Layer Gateway"?

A security component that filters network traffic for a specific application.

44. What is "Wi-Fi" (802.11)?

A wireless networking technology that allows devices such as computers and mobile phones to interface with the internet.

45. What is the difference between "Unicast", "Multicast", and "Broadcast"?

Unicast: One-to-one.
Multicast: One-to-many (specific group).
Broadcast: One-to-all.

46. What is "Loopback Address" (127.0.0.1)?

An IP address that points to the local machine, used for testing purposes.

47. What is "Piggybacking"?

A technique in data transmission where the acknowledgement of a received packet is included in the next outgoing data packet.

48. What is "Quality of Service" (QoS)?

A set of network technologies that prioritize specific traffic (like voice or video) to ensure reliable performance.

49. What is "Flow Control"?

The process of managing the rate of data transmission between two nodes to prevent the fast sender from overwhelming a slow receiver.

50. What is the "Network Address"?

The first address in a subnet, used to identify the entire network itself.

Computer Networks Interview Questions

Table of Contents

What is a "Computer Network"?

What are the key components of a Network?

What is the "OSI Model"?

Name the 7 Layers of the OSI Model?

What is the "TCP/IP Model"?

What is the difference between "Hub", "Switch", and "Router"?

What is an "IP Address"?

What's the difference between "IPv4" and "IPv6"?

What is "MAC Address"?

What is "TCP" (Transmission Control Protocol)?

What is "UDP" (User Datagram Protocol)?

What is "DNS" (Domain Name System)?

What is "HTTP" vs "HTTPS"?

What is "DHCP" (Dynamic Host Configuration Protocol)?

What is "ARP" (Address Resolution Protocol)?

What is "ICMP" (Internet Control Message Protocol)?

What is a "Subnet"?

What is "Default Gateway"?

What is "NAT" (Network Address Translation)?

What is a "Firewall"?

What is a "VPN" (Virtual Private Network)?

What is the difference between "Bandwidth" and "Latency"?

What is "Jitter"?

What is "CSMA/CD" and "CSMA/CA"?

What is "Three-Way Handshake"?

What is "FTP" (File Transfer Protocol)?

What is "SMTP", "POP3", and "IMAP"?

What is the "BGP" (Border Gateway Protocol)?

What is "Socket" in Networking?

What is "Port"?

What is "Proxy Server"?

What is "SSL/TLS"?

What is "Network Topology"?

What is "Star Topology"?

What is "Mesh Topology"?

What is "Collision Domain"?

What is "Broadcast Domain"?

What is "NFS" (Network File System)?

What is "SSH" (Secure Shell)?

What is "Telnet"?

What is "Ping"?

What is "Traceroute"?

What is the "Application Layer Gateway"?

What is "Wi-Fi" (802.11)?

What is the difference between "Unicast", "Multicast", and "Broadcast"?

What is "Loopback Address" (127.0.0.1)?

What is "Piggybacking"?

What is "Quality of Service" (QoS)?

What is "Flow Control"?

What is the "Network Address"?