Most Asked Computer Network Interview Questions

 Most Asked Computer Network Interview Questions:

1. What is a computer network?

• Answer: A computer network is a collection of interconnected devices (computers, servers, routers, switches, etc.) that can communicate and share resources with each other.

2. What is the OSI model, and why is it important in networking?

• Answer: The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers. It is important as it provides a common reference point for understanding and discussing network protocols and operations.

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

• Answer:
  • A hub operates at the physical layer (Layer 1) and simply broadcasts data to all devices on a network.
  • A switch operates at the data link layer (Layer 2) and makes forwarding decisions based on MAC addresses.
  • A router operates at the network layer (Layer 3) and routes data between different IP subnets.

4. What is an IP address, and how is it structured?

• Answer: An IP address is a numerical label assigned to each device participating in a computer network. It is structured as a series of four numbers (IPv4) or eight groups (IPv6), separated by periods or colons, respectively.

5. What is the difference between IPv4 and IPv6?

• Answer: IPv4 uses a 32-bit address format, allowing for approximately 4.3 billion unique addresses, while IPv6 uses a 128-bit address format, offering an immensely larger address space, accommodating trillions of unique addresses.

6. What is a subnet mask?

• Answer: A subnet mask is used in networking to divide an IP address into a network portion and a host portion. It consists of a series of 1s followed by 0s, with the 1s indicating the network portion.

7. What is a MAC address?

• Answer: A MAC (Media Access Control) address is a hardware address assigned to network interface cards and is used for communication within a local network. It is a unique identifier for each network device.

8. Explain the difference between TCP and UDP.

• Answer: TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures data reliability and in-order delivery. UDP (User Datagram Protocol) is connectionless and offers minimal error-checking, making it suitable for applications where speed is more critical than accuracy.

9. What is a DNS server, and why is it important?

• Answer: A DNS (Domain Name System) server translates human-readable domain names into IP addresses. It is important because it simplifies the process of reaching websites by name, as opposed to using numerical IP addresses.

10. What is a firewall? - Answer: A firewall is a network security device or software that monitors and controls incoming and outgoing network traffic based on predetermined security rules, protecting a network from unauthorized access and cyber threats.

11. Explain NAT (Network Address Translation). - Answer: NAT is a method that modifies network address information in packet headers while in transit to make it appear as if it originates from a different IP address. It is commonly used to allow multiple devices on a private network to share a single public IP address.

12. What is a VLAN (Virtual Local Area Network)? - Answer: A VLAN is a logical network created within a physical network that allows devices to communicate as if they were on the same physical network, even if they are physically located in different places.

13. What is ARP (Address Resolution Protocol)? - Answer: ARP is used to map an IP address to a MAC address within a local network. It helps devices discover each other on the same network.

14. What is a subnet? - Answer: A subnet is a smaller, segmented network created from a larger network. It helps in optimizing network performance, security, and management.

15. Explain the purpose of the DHCP server. - Answer: DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and network configuration settings to devices on a network, simplifying network administration.

16. What is a proxy server? - Answer: A proxy server acts as an intermediary between client devices and servers. It can provide anonymity, content filtering, and caching for improved performance and security.

17. What is a MAC flooding attack? - Answer: A MAC flooding attack involves sending a flood of frames with different MAC addresses to a switch, causing it to overflow its MAC address table and potentially allowing an attacker to intercept traffic.

18. What is a DDoS attack? - Answer: A DDoS (Distributed Denial of Service) attack floods a network or server with a massive volume of traffic from multiple sources, overwhelming the target and making it inaccessible to legitimate users.

19. What is a man-in-the-middle attack? - Answer: A man-in-the-middle attack involves intercepting and possibly altering communications between two parties without their knowledge, often used for eavesdropping or data manipulation.

20. What is QoS (Quality of Service) in networking? - Answer: QoS is a set of technologies and policies used to manage and prioritize network traffic to ensure that critical applications receive sufficient bandwidth and resources for optimal performance.

21. What is the purpose of a VPN (Virtual Private Network)? - Answer: A VPN provides secure and encrypted connections over a public network, such as the internet, to enable remote users to access a private network as if they were physically on-site.

22. Explain the difference between half-duplex and full-duplex communication. - Answer: Half-duplex communication allows data transmission in only one direction at a time, while full-duplex communication allows simultaneous two-way communication.

23. What is a gateway in networking? - Answer: A gateway is a device that connects two or more networks with different protocols, allowing them to communicate and share data.

24. What is a packet and how does it relate to network communication? - Answer: A packet is a unit of data transmitted over a network. It contains both the data being transferred and control information, including source and destination addresses.

25. What is the purpose of a traceroute command? - Answer: Traceroute is used to trace the path that packets take from a source to a destination by listing all the intermediate routers or switches along the way.

26. What is the purpose of the ping command? - Answer: The ping command is used to test the reachability of a host on a network and measure the round-trip time for packets to travel to the host and back.

27. What is a subnet in CIDR notation? - Answer: CIDR (Classless Inter-Domain Routing) notation represents a subnet by combining the network address and the number of bits in the subnet mask. For example, "192.168.1.0/24" represents a subnet with a 24-bit subnet mask.

28. What is a MAC filtering in the context of wireless networks? - Answer: MAC filtering allows or denies access to a wireless network based on the MAC address of a device. It is a basic security measure for controlling network access.

29. What is a BGP (Border Gateway Protocol)? - Answer: BGP is an exterior gateway protocol used to manage routing and connectivity between different autonomous systems (ASes) on the internet.

30. What is a 802.1Q VLAN Tagging? - Answer: 802.1Q VLAN tagging is a method used to identify VLAN membership in Ethernet frames by adding a tag with the VLAN ID to the frame header.

31. Explain the purpose of ARP poisoning. - Answer: ARP poisoning, also known as ARP spoofing, is a network attack where an attacker sends fake ARP (Address Resolution Protocol) messages to associate their MAC address with the IP address of another network device, enabling them to intercept or manipulate traffic.

32. What is a broadcast domain? - Answer: A broadcast domain is a logical division of a network in which all devices can directly communicate with each other by broadcasting messages. Routers separate broadcast domains.

33. What is the purpose of a DMZ (Demilitarized Zone) in network security? - Answer: A DMZ is a network segment that is isolated from the internal network and the internet. It is used to host public-facing services, such as web servers, while keeping them separate from the internal network for security.

34. Explain the difference between static routing and dynamic routing. - Answer: Static routing involves manually configuring routing tables, while dynamic routing uses routing protocols to automatically update and adapt routing information based on network changes.

36. What is a MAC layer in the OSI model, and what is its role?

• Answer: The MAC (Media Access Control) layer is part of the data link layer (Layer 2) in the OSI model. Its role is to control access to the physical transmission medium, manage frame addressing, and handle error detection and correction.

37. What is a subnet in IPv6?

• Answer: In IPv6, subnets are defined by using a prefix length in CIDR notation. For example, "2001:0db8:85a3::/64" represents an IPv6 subnet with a prefix length of 64 bits.

38. What is a default gateway?

• Answer: A default gateway is a device or router that connects a local network to external networks, such as the internet. It is used as the route for traffic that is not destined for the local network.

39. What is a 802.1X authentication in network security?

• Answer: 802.1X is an IEEE standard for network access control that provides port-based authentication, ensuring that only authorized devices can access the network.

40. What is a MACsec (MAC Security) protocol?

• Answer: MACsec is a security protocol that provides data confidentiality, data integrity, and data origin authentication for data transmitted over Ethernet networks.

41. What is the purpose of the ping of death attack?

• Answer: The ping of death is a network attack that involves sending an oversized or malformed ping packet to a target system, causing it to crash or become unresponsive.

42. What is a proxy ARP?

• Answer: Proxy ARP is a network technique in which one device, often a router, answers ARP requests on behalf of another device to make it appear as if it is part of the local network, allowing traffic to be routed through the proxy device.

43. What is a subnet broadcast address?

• Answer: The subnet broadcast address is the highest possible address within a subnet, which is used to send broadcast messages to all devices in that subnet.

44. What is the purpose of STP (Spanning Tree Protocol)?

• Answer: STP is a network protocol that prevents loops in Ethernet networks by determining the most efficient path for data to travel, disabling redundant links to avoid network instability.

45. What is the difference between symmetric and asymmetric encryption?

• Answer: In symmetric encryption, the same key is used for both encryption and decryption. In asymmetric encryption, two different keys (a public key for encryption and a private key for decryption) are used, providing better security but requiring more computational resources.

46. What is a DNS resolver?

• Answer: A DNS resolver is a client-side application or service that converts domain names into IP addresses by querying DNS servers.

47. What is NAT traversal, and why is it important in network communication?

• Answer: NAT traversal is the process of enabling network communication to pass through network address translation (NAT) devices, allowing devices behind NATs to communicate with devices on the public internet. This is crucial for peer-to-peer communication and many internet applications.

48. What is the purpose of ICMP (Internet Control Message Protocol)?

• Answer: ICMP is a network layer protocol used to send error and informational messages, such as ping requests and responses, to report network conditions or issues.

49. What is the role of a DNS root server?

• Answer: DNS root servers are the starting point for the DNS resolution process. They store the information necessary to locate top-level domain (TLD) name servers, such as .com or .org, and direct DNS queries to the appropriate TLD servers.

50. What is a honey pot in network security?

• Answer: A honey pot is a security mechanism designed to lure potential attackers into a controlled environment. It helps security professionals study and analyze attack techniques and tactics without risking the security of the actual network.