Computer Network Interview Questions

Here are the top 50 commonly asked questions in Computer Network interviews. Whether you’re just starting your preparation or need a quick refresher, these questions and answers will help you tackle your interview with confidence.

Basic Computer Network Interview Questions with Answers

1. What is a computer network?

A computer network is a set of devices or nodes communicating via links. These devices communicate with each other in order to share resources and exchange data. All the devices in the network are capable of transmitting and receiving data using the same communication protocols.

2. What is a node in a computer network?

A node in a computer network is a device capable of generating, transmitting and receiving data produced by others devices in the same network. A node is otherwise referred to as a station or system. Some examples of nodes include printers, computers, modem and so on.

3. What is a link in a computer network?

A link in a computer network is the physical interface or medium through which the data generated by the nodes in the computer network, is transmitted. It can be a cable, optical fiber, air, radio waves or any other physical medium capable of transporting a signal containing some information.

4. What is the use of gateway in a computer network?

A gateway acts as an entry point to a computer network. It manages all the inflow and outflow of data from a computer network. A gateway is capable of connecting two dissimilar networks using different transmission protocols. Unlike the other networking devices, the gateway can act in any layer of the network architecture model.

5. What is the use of firewall in a computer network?

A firewall is a hardware or software – based device responsible for monitoring the network security and filtering the inflow of data from the external untrusted sources. The data traffic satisfying a defined set of security protocols is only allowed to enter the secured internal network. This prevents any malicious external software from accessing the confidential information from the internal networks.

6. How does the proxy server protect the computer network?

A proxy server acts as an intermediate server between the users and the website requested by the users. When a user makes a web request, this request is transferred to the proxy server which then makes the web request on behalf of the user, collects the response from the web server and then proceeds to send the data to the user. This prevents end users and internal networks from being attacked by malicious software in the Internet.


7. What is the use of NIC in a computer network?

Network Interface Card (NIC) is a component which allows a device to connect to a computer network. It provides the devices a dedicated, reliable and secure connection to the network. It manages the wired and wireless communications of devices in order to exchange information with other devices.

8. What is the use of MAC address in a computer network?

MAC address is a unique 12 – digit hexadecimal address associated with the Network Interface Card (NIC). MAC address is also referred to as physical address or hardware address or link layer address or burned – in address as this address is hard – wired at the time of manufacturing and is unique to that particular network adaptor. This hardware address is responsible for forwarding of data between intermediate devices.

9. What is the use of IP address in a computer network?

IP address also called the global address or network address or logical address, is used to uniquely identify a device on the computer network. Routing of transmitted data is done with the help of IP addresses of the source and destination. The IP addresses of devices are not unique and may vary over a certain time period.

10. What is the use of ipconfig command in computer network?

IPCONFIG stands for Internet Protocol Configuration. It is a command – line utility which displays some additional information such as the device’s currently assigned IP address, IP addresses of the DNS servers being used, subnet mask in addition to the TCP/IP configuration of the network. It also displays the enabled and disabled configurations of connected devices.

11. What is the use of ifconfig command in a computer network?

IFCONFIG stands for Internet Configuration. As the name suggests, ifconfig command is used for the configuration of the network interface parameters or assignment of address to the network interface or to display the information of the current network interface configuration. This command is often used in UNIX – like operating systems.

12. What is data encapsulation in a computer network?

Data encapsulation in a computer network is the addition or binding of some additional information to data during its transmission. Every layer of the OSI and TCP/IP model binds some information such as headers and trailer at the sender side. For example, the IP addresses of the source and destination are included in the header of the packet in the network layer.

13. What is the use of ping command in a computer network?

Ping command is used in a computer network to check the connectivity or reachability of a remote host. An echo request is sent to a remote address to check if it’s accessible. If the echo request is delivered to the destination host and the host is able to respond with an echo reply, then the host is considered to be alive and reachable.

14. What is the use of beacon frames in a computer network?

Beacon frame is a management frame used in IEEE 802.11 WLAN. In a WLAN, the access point and the devices periodically publicize their presence using the beacon frames. These frames are used to synchronize devices and contain network information such as the traffic map, timestamp, SSID, beacon interval and so on.

15. What is encoding in a computer network?

Encoding in computer network is the process of conversion of data such as images, text, audio, video into a binary pattern or code for secure and efficient transmission of data.


16. What is congestion in a computer network?

Congestion in a computer network occurs as a consequence of excess load on the network. If the nodes or links of the network carry large amount of data which exceeds the maximum capacity of the network, this may lead to deterioration in the performance of the network and may induce delay in transfer of data.

17. What is downtime in a computer network?

Downtime is the time taken for a computer network to recuperate from failure and during this recovery time, the network is unavailable for data transmission. A network may be down due to multiple reasons such as software or hardware failure, traffic overload, outage of power and so on.

18. What is the Protocol Data Unit (PDU) in a computer network?

Protocol Data Unit (PDU) is a term used to address a unique block of information added or removed at each layer of the OSI model. Each layer uses a different PDU which can only be decoded by the corresponding layers at the sender and receiver sites. For example, the PDU of physical layer is bits i.e., 0s and 1s whereas the PDU of network layer is packets containing the IP addresses.

19. What is the use of Telnet in computer network?

Terminal Network (Telnet) is an application layer protocol which allows end users to remotely access or log into another computer. It allows users of one machine to access an application program and utilize its resources remotely in another machine.

20. What is the role of port numbers in a computer network?

Port Numbers facilitate process – to – process delivery on a computer network. There might be multiple applications or processes running on the same system. In order to distinguish these processes, each of these processes is assigned a 16 – bit port number. For example, port number 25 is used by SMTP, a message transfer agent responsible for transferring electronic mail.


Intermediate Computer Network Interview Questions with Answers

21. What is crossover cable?

Crossover cable is an Ethernet cable which is used to connect alike or similar type of devices and both ends must follow similar wiring standards. The transmission and reception pins at both the ends are reversed, such that the output from one computer acts as an input to another computer.

22. What is Round Trip Time?

Round Trip Time (RTT) is the sum of the time taken for data to be transmitted from source to destination and the time taken for the acknowledgement of the delivered data to be delivered to the source. The maximum value of Round Trip Time is twice the propagation time.

23. What is a Brouter?

Bridge Router (Brouter) is a networking device capable of operating as a bridge as well as a router. It can function in network and datalink layers of the network model. It can transfer data packets to other networks when functioning as a bridge and also route data packets to other devices within the network when functioning as a router.

24. What is Static IP?

Static IP is the IP address assigned to a system by the Internet Service Provider (ISP). As the name suggests, static IP addresses are fixed and do not change as long as the system is connected to the network.

25. What is Dynamic IP?

Dynamic IP is the IP address assigned temporarily to a system using Dynamic Host Configuration Protocol (DHCP). The dynamic IP addresses can be changed over time according to the user’s requirement. DHCP servers maintain a pool of IP addresses from which an IP address is temporarily assigned to the system.

26. What is encryption?

Encryption is the process of converting human understandable text to unintelligible format called cipher text using certain mathematical procedures such that only an authorized user is able to decode it to retrieve the original data.

27. What is throughput?

Throughput is the actual measure of data that can be transferred in a computer network. It is measured in terms of bits per second (bps).

28. What is peer – to – peer network?

Peer – to – peer network is a decentralized network in which there is no central controller. Each node can request as well as offer services i.e., send and receive data at their own convenience. The workload is also evenly distributed among all nodes or peers.

29. What is client – server network?

Client – server network is a centralized network in which there exist two types of devices called client and server. Client requests services from the server and the server is responsible for the provision of the requested services.

30. What is Serial Line Internet Protocol?

Serial Line Internet Protocol (SLIP) is an internet communication protocol responsible for data transfer over serial transmission lines. It supports TCP/IP networking over serial ports and routers. It offers dial – up access to Internet using the SLIP servers at the ISP.

31. What is an edge router?

Edge router is a dedicated router that resides at the boundary of a network in order to connect the internal network to the external networks. Edge routers accept the inbound data traffic flowing into the network.

32. What is a Public IP?

Public IP address is a global address which allows direct access to the Internet. It facilitates communication outside the local network. These IP addresses are allotted by the Internet Service Provider (ISP) and helps to connect to the Internet from the internal network.

33. What is a Private IP?

Private IP address is a local address assigned to the system by the local network router. It facilitates communication between devices within the same internal network and doesn’t allow external devices to establish a connection with internal network devices.

34. What is PoE?

Power over Ethernet (PoE) technology allows the devices to deliver electrical power by means of network cables. This eradicates the need for separate power outlets and supplies to deliver electrical power and saves cost by transmitting data and power over a single cable.

35. What is address depletion?

Address depletion is the exhaustion of allocated IPv4 addresses for connected devices. IPv4 supported classful addressing in which class B address space was getting depleted soon with the increase in the number of users due to its fair balance between the number of networks and hosts. Whereas class A supported more hosts than required while class C supported very few hosts.

36. What is Point – to – Point Protocol?

Point – to – Point Protocol (PPP) is a communication protocol operating in the datalink layer in order to facilitate the transfer of multiprotocol packets between two devices connected via a point – to – point link. It comprises of data encapsulation protocol, link control protocol and network control protocols.

37. What is MTU?

Maximum Transmission Unit (MTU) is the maximum size of the payload of a frame. It depends on the datalink and physical layer protocols. The MTU of Standard Ethernet with data rate of 10 or 100 Mbps is 1500 bytes.

38. What is an autonomous system?

An autonomous system (AS) is a collection of networks and routers governed by a single administration. All the devices and routers in the AS follow the same routing policy. Each AS can choose their desired intradomain routing protocols to handle routing within the AS.

39. What is Basic Service Set?

Basic Service Set (BSS) is a collection of stationary or mobile wireless stations within IEEE 802.11 network. The stations may communicate with each other with the help of the optional central base station known as Access Point (AP).

40. What is Extended Service Set?

Extended Service Set (ESS) is a collection of two or more Basic Service Sets (BSSs). The BSSs may be connected by means of wired or wireless networks. Each BSS consists of one or more wireless stations and an optional access point.

41. What is piconet?

Piconet is a Bluetooth network consisting of at most 8 stations out of which one is primary station and the others are secondary stations. The communication between the primary and secondary stations may be one – to – many or one – to – one communication.

42. What is scatternet?

Scatternet is a Bluetooth network formed by combining two or more piconets. In a scatternet, the primary station of one piconet may be a secondary station of another piconet. This station is referred to as bridge node as it bridges the two piconets.

43. What is the use of tracert command?

Tracert command is used to display or trace the paths to be taken in order to reach the required destination host. This command displays the list of routers a packet must be forwarded to in order to reach any device in the network. Tracert command is available on Windows only.

44. What is the use of traceroute command?

Traceroute is a widely used command line utility available in Windows as well as Linux. This command is used to track the real – time routes taken by the packet from the source to destination. It records the time taken for the packet to reach each intermediate router and the IP addresses of all the pinged intermediate routers.

45. What is bit rate?

Bit rate in a computer network can be simply defined as the number of bits that can be transmitted over the channel in unit time. It is usually measured in bits per second (bps).

46. What is baud rate?

Baud rate in a computer network is the number of voltage level changes that occurs in a transmitted signal in unit time. It is associated with the number of times the signal carrying information bits alters. It is usually measured in bauds per second.

47. What is a point – to – point link?

Point – to – point link in a computer network is a link that is reserved for connecting two particular devices. This dedicated link between the two connected devices only carries the data traffic with respect to those two devices.

48. What is layering?

The functions of a network architecture model is split into multiple blocks for the ease of data transmission. The decomposition of the network into multiple components or layers is called layering. Each layer of the network model is associated with one particular function. This provides a modular design of the network.

49. What is Bandwidth – Delay product?

Bandwidth – Delay product is the measure of number of bits that can occupy a link at a time. For example, if bandwidth is 10 bps and delay is 5 seconds, then the bandwidth – delay product is 50 bits i.e., 50 bits can simultaneously be transmitted on the link at a time.

50. What is multiplexing?

Multiplexing in a computer network is the process of combining several data streams and transmit them together on the same communication link. In multiplexing, the capacity of a single channel is divided in order to accommodate multiple data streams. Multiplexing is used in process – to – process delivery to combine information of all process and display them on the same system.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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