Top 50 Computer Networking Interview questions and answers – GeeksforGeeks

1. Name two technologies by which you would connect two offices in remote locations. Two technologies by which would connect two offices in outside locations are VPN and Cloud calculation. 2. What is internetworking?

Internetworking is a combination of two words, bury and network which implies an affiliation between wholly different nodes or segments. This connection sphere whole is established through mediator devices akin to routers or gateway. The first term for associate degree internetwork was interconnected. This interconnection is frequently among or between public, private, commercial, industrial, or governmental networks. therefore, associate degree internetwork could be an assortment of individual networks, connected by intercede network devices, that affair as one giant network. Internetworking refers to the trade, products, and procedures that meet the challenge of making and administering internet works. 3. Name of the software layers or User support layer in OSI model.

  • Application layer
  • Presentation layer
  • Session layer

4. Name of the hardware layers or network support layer in OSI model.

  •  Network layer
  • Datalink layer
  • Physical layer

5. Define HTTPS protocol? The full form of HTTPS is Hypertext transfer protocol fasten. It is an progress adaptation of the HTTP protocol. Its port number is 443 by nonpayment. It uses SSL/TLS protocol for providingsecurity. 6. Name some services provided by the application layer in the Internet model? Some services provided by the application layer in the Internet model are as follows :

  • Mail services
  • Directory services
  • File transfer
  • Access management
  • Network virtual terminal

7. In which OSI layer is the header and trailer added? At Data radio link layer trailer is added and at OSI model layer 6,5,4,3 add header. 8. What happens in the OSL model, as a data packet moves from the lower to upper layers? In the OSL model, as a data packet moves from the lower to upper layers, headers get removed. 9. What happens in the OSL model, as a data packet moves from the upper to lower layers? In the OSL model, as a data mailboat moves from the lower to amphetamine layers, headers are added. This header contains utilitarian information. 10. What is zone-based firewall? A Zone-based firewall is an advance method acting of the stateful firewall. In a stateful firewall, a stateful database is maintained in which generator IP address, destination IP address, generator port number, address port issue are recorded. due to this, only the replies are allowed i.e if the traffic is Generated from inside the network then lone the replies ( of inside network traffic ) coming from outside the network is allowed. Cisco IOS router can be made firewall through two methods :

  1. By using CBAC: create an access list and apply it to the interfaces keeping in mind what traffic should be allowed or denied and in what direction. This has an extra overhead for the administrator.
  2. Using a Zone-based firewall.

For more details please refer Zone-based firewall article. 11. What is a server farm? A waiter grow is a sic of many servers interconnected in concert and housed within the lapp physical facility. A server farm provides the combine computing exponent of many servers by simultaneously executing one or more applications or services. A server farm is broadly a separate of an enterprise data focus on or a component of a supercomputer. A waiter farm is besides known as a server cluster or computer ranch. 12. Name the three means of user authentication. There is biometrics ( e.g. a thumbprint, iris scan ), a token, or a password. There is besides two-level authentication, which employs two of those methods. 13. What is Confidentiality, Integrity &  Availability? Confidentiality – means information is not disclosed to unauthorized individuals, entities, and processes. For model, if we say I have a password for my Gmail history but person saw while I was doing a login into Gmail account. In that case, my password has been compromised and Confidentiality has been breached. Integrity – means maintaining accuracy and completeness of data. This means data can not be edited in an unauthorized way. For exemplar, if an employee leaves an arrangement then in that case data for that employee in all departments like accounts, should be updated to reflect condition to JOB LEFT so that datum is complete and accurate and in summation, this is merely authorize person should be allowed to edit employee data. Availability – means information must be available when needed. For model, if one needs to access information of a particular employee to check whether an employee has outstood the number of leaves, in that case, it requires collaboration from different organizational teams like network operations, exploitation operations, incident response, and policy/change management.
Denial of service attack is one of the factors that can hamper the handiness of information. 14. What is VPN? VPN stands for the virtual individual network. A virtual private network ( VPN ) is a engineering that creates a condom and code association over a less guarantee network, such as the internet. A virtual Private Network is a manner to extend a private network using a public network such as the internet. The name alone suggests that it is a virtual “ private net ” i.e. drug user can be separate of a local anesthetic network sitting at a distant location. It makes consumption of tunneling protocols to establish a procure connection. For more details please refer VPN article 15. What is Symmetric and Asymmetric Encryption? Symmetric Key Encryption:
Encryption is a summons to change the shape of any message in order to protect it from reading by anyone. In Symmetric-key encoding the message is encrypted by using a key and the same keystone is used to decrypt the message which makes it easy to use but less impregnable. It besides requires a safe method acting to transfer the winder from one party to another. Asymmetric Key Encryption:
Asymmetric Key Encryption is based on populace and secret key encoding techniques. It uses two unlike keys to encrypt and decrypt the message. It is more secure than the symmetrical key encoding technique but is much slower. For more details please refer remainder between symmetrical and asymmetrical encoding articles.  16. At what layer IPsec works? An IPsec works on layer 3 of the OSI model. 17. What is a Tunnel mode? This is a mode of data exchange wherein two communicating computers do not use IPSec themselves. rather, the gateway that is connecting their local area network to the transit network creates a virtual burrow that uses the IPSec protocol to secure all communication that passes through it. Tunnel manner is most normally used between gateways, or at an end-station to a gateway, the gateway acting as a proxy for the hosts behind it. Tunnel mode is most normally used to encrypt traffic between dependable IPSec gateways, such as between the Cisco router and PIX Firewall 18. Define Digital Signatures? As the name sounds are the new alternate to sign a document digitally. It ensures that the message is sent to the intended manipulation without any meddle by any third party ( attacker ). In childlike words, digital signatures are used to verify the authenticity of the message sent electronically. or we can say that – A digital signature is a mathematical technique used to validate the authenticity and integrity of a message, software, or digital document.
19. What is Authorization? Authorization provides capabilities to enforce policies on network resources after the user has gained access to the network resources through authentication. After the authentication is successful, authority can be used to determine what resources is the drug user allowed to entree and the operations that can be performed. 20. What is the difference between IPS and a firewall? The intrusion Prevention System is besides known as Intrusion Detection and Prevention System. It is a network security application that monitors network or organization activities for malicious action. The major functions of invasion prevention systems are to identify malicious bodily process, collect information about this action, report card it and attempt to block or stop it. Intrusion prevention systems are contemplated as augmentation of Intrusion Detection Systems ( IDS ) because both IPS and IDS operate network dealings and system activities for malicious natural process. IPS typically records information related to observe events, notifies security administrators of significant note events, and produces reports. many IPS can besides respond to a detected threat by attempting to prevent it from succeeding. They use versatile response techniques, which involve the IPS stopping the attack itself, changing the security environment, or changing the attack ’ south message. A firewall is a network security device, either hardware or software-based, which monitors all incoming and outgoing traffic, and based on a defined set of security system rules it accepts, rejects, or drops that particular traffic.  21.What is IP Spoofing? IP Spoofing is basically a technique used by hackers to gain unauthorized access to Computers. Concepts of IP Spoofing were initially discussed in academician circles a early as 1980. IP Spoofing types of attacks had been known to Security experts on the theoretical level. It was chiefly theoretical until Robert Morris discovered a security helplessness in the TCP protocol known as succession prediction. occasionally IP spoof is done to mask the origins of a Dos attack. In fact, Dos attacks much mask the actual IP addresses from where the attack has originated from. 22. What is the meaning of threat, vulnerability, and risk? Threats are anything that can exploit a vulnerability by chance or intentionally and destroy or damage an asset. An asset can be anything people, property, or information. The asset is what we are trying to protect and a menace is what we are trying to protect against. Vulnerability means a gap or weakness in our protection efforts. risk is nothing but an intersection of assets, threats, and vulnerability .

A+T+V = R

23. What is the main purpose of a DNS server? DNS stands for Domain Name Server. It translates Internet sphere and hostnames to IP addresses and vice versa. DNS technology allows typing names into your Web browsers and our calculator to automatically find that address on the Internet. A key component of the DNS is a global collection of DNS servers. It has the responsibility of assigning domain names and mapping those names to Internet resources by designating an authoritative name server for each domain. The Internet maintains two main namespaces like Domain Name hierarchy and Internet protocol addresses space.  24. What is the protocol and port no of DNS? Protocol – TCP/UDP Port number- 53 25. What is the position of the transmission media in the OSI model? In the OSI exemplary, transmission media supports layer-1 ( Physical level ). 26. What is the importance of twisting in the twisted-pair cable? The twisted-pair cable consists of two insulate copper wires twisted together. The twist is important for minimizing electromagnetic radiation and external hindrance.

27. What kind of error is undetectable by the checksum? In checksum, multiple bit errors can not be undetectable. 28. Which multiplexing technique is used in the Fiber-optic links ? The wavelength division multiplexing is normally used in fiber ocular links. 29. What are the Advantages of Fiber Optics?

  • Bandwidth is above copper cables
  • Less power loss and allows data transmission for extended distances
  • The optical cable is resistant to electromagnetic interference
  • Fiber cable is sized 4.5 times which is best than copper wires
  • As the cable is lighter, thinner, in order that they use less area as compared to copper wires
  • Installation is extremely easy thanks to less weight.
  • Optical fiber cable is extremely hard to tap because they don’t produce electromagnetic energy. These optical fiber cables are very secure for transmitting data.
  • This cable opposes most acidic elements that hit copper wired also are flexible in nature.
  • Optical fiber cables are often made cheaper than equivalent lengths of copper wire.
  • Light has the fastest speed within the universe, such a lot faster signals
  • Fiber optic cables allow much more cable than copper twisted-pair cables.
  • Fiber optic cables have how more bandwidth than copper twisted-pair cables.

30.Which of the multiplexing techniques are used to combine analog signals? To combine analogue signals, normally FDM ( Frequency division multiplexing ) and WDM ( Wavelength-division multiplexing ) are used. 31. Which of the multiplexing techniques is used to combine digital signals? To combine digital signals, time division multiplexing techniques are used. 32. Can IP Multicast be load-balanced? No, The information science multicast multipath instruction load splits the traffic and does not load balance the traffic. traffic from a reservoir will use only one path, even if the traffic far outweighs dealings from other sources. 33. What is CGMP(cisco group management protocol)? CGMP is a simple protocol, the routers are the only devices that are producing CGMP messages. The switches merely listen to these messages and act upon it. CGMP uses a long-familiar finish MAC address (0100.0cdd.dddd) for all its messages. When switches receive frames with this address address, they flood it on all their interfaces which so all switches in the net will receive CGMP messages. Within a CGMP message, the two most important items are :

  • Group Destination Address (GDA)
  • Unicast Source Address (USA)

The group destination address is the multicast group MAC address, the unicast source address is the MAC address of the horde ( receiver ).  34. What is Multicast? Multicast is a method of group communication where the sender sends data to multiple receivers or nodes present in the network simultaneously. Multicasting is a type of one-to-many and many-to-many communication as it allows sender or senders to send data packets to multiple receivers at once across LANs or WANs. This process helps in minimizing the datum frame of the network. For more details please read Multicasting in calculator network article. 35. What is the difference between Bluetooth and wifi? 

S.NO Bluetooth Wifi
1. Bluetooth has no full form. While wifi stands for Wireless Fidelity.
2. It requires bluetooth adapter on all devices for connectivity. Whereas it requires a wireless adapter Bluetooth for all devices and a wireless router for connectivity.
3. Bluetooth consumes low power. while it consumes high power.
4. The security of BlueTooth is less in comparison to the number of wifi. While it provides better security than BlueTooth.
5. Bluetooth is less flexible means these limited users are supported. Whereas wifi supports large amount of users.
6. The radio signal range of BlueTooth is ten meters. Whereas in wifi this range is a hundred meters.
7. Bluetooth requires low bandwidth. While it requires high bandwidth.

36. What is a reverse proxy? Reverse Proxy Server: The speculate of a turn back proxy server to listen to the request made by the client and redirect to the detail world wide web server which is present on different servers. This is besides used to restrict the access of the clients to the confidential data residing on the particular servers. For more details please refer what is proxy server article.
37. What is the role of address in packet traveling through a datagram network? The address field in a datagram network is end-to-end cover. 38. Can a routing table in the datagram network have two entries with the same destination address? No. routing tables in the datagram network have two entries with the same finish address, not potential because the address address or liquidator address is singular in the datagram net. 39. What kind of arithmetic is used to add data items in checksum calculation? To add data items in checksum calculations, one ’ mho complement arithmetic is used. 40. Define piggybacking? A proficiency called piggyback is used to improve the efficiency of the bidirectional protocols. When a frame is carrying data from A to B, it can besides carry control information about arrived ( or lost ) frames from B ; when a skeletal system is carrying data from B to A, it can besides carry master information about the arrive ( or lost ) frames from A. 41. What are the advantages and disadvantages of piggybacking? The major advantage of piggyback is better use of available channel bandwidth. The major disadvantage of piggybacking is extra complexity and if the data liaison level waits besides long before transmitting the acknowledgment, then re-transmission of the frame would take place . 42. Which technique is used in byte-oriented protocols? A byte stuff is used in byte-oriented protocols. A particular byte is added to the data section of the frame when there is a fictional character with the same pattern as the flag. 43. Define the term OFDM? Orthogonal Frequency Division Multiplexing (OFDM):
It is besides the multiplexing proficiency that is used in an analogue system. In OFDM, the Guard dance band is not required and the apparitional efficiency of OFDM is high which oppose to the FDM. In OFDM, a Single data generator attaches all the sub-channels. 44. What is a transparent bridge? Transparent Bridge:
A guileless bridge automatically maintains a rout table and updates tables in answer to maintain changing topology. The transparent bridge mechanism consists of three mechanisms :

  • Frame forwarding
  • Address Learning
  • Loop Resolution

The Transparent bridge is easy to use. Install the bridge and no software changes are needed in hosts. In all the cases, diaphanous bridges flooded the broadcast and multicast frames. 45. What is the minimum size of the icmpV4 packet what is the maximum size of the icmpv4 packet?

  • Minimum size ICMPv4 packet = 28 bytes
  • Maximum size ICMPv4 packet = 2068 bytes

46. Why do we OSPF a protocol that is faster than our RIP? OSPF stands for Open Shortest Path First which uses a link-state rout algorithm. This protocol is faster than RIP because :

  • Using the link-state information which is available in routers, it constructs the topology in which the topology determines the routing table for routing decisions. 
  • It supports both variable-length subnet masking and classless inter-domain routing addressing models. 
  • Since it uses Dijkstra’s algorithm, it computes the shortest path tree for each route. 
  •  OSPF (Open Shortest Path first) is handling the error detection by itself and it uses multicast addressing for routing in a broadcast domain

47. What are the two main categories of DNS messages? The two categories of DNS messages are queries and replies. 48. Why do we need the pop3 protocol for e-mail? Need of POP3:   The Post Office Protocol ( POP3 ) is that the most wide used protocol and is being supported by most electronic mail clients. It provides a commodious and standard way for users to access mailboxes and download messages. An crucial advantage of this is that the mail messages get delivered to the customer ’ south personal computer and they can be read with or without accessing the vane. 49. Define the term Jitter? jitter is a “ packet stay variance ”. It can plainly mean that jitter is considered as a problem when different packets of data face unlike delays in a net and the data at the receiver application is time-sensitive, i.e. audio or video recording data. Jitter is measured in milliseconds ( meter ). It is defined as an hindrance in the normal order of sending data packets. 50. Why Bandwidth is an important to network performance parameter? Bandwidth is characterized as the quantify of data or information that can be transmitted in a repair measure of time. The term can be used in two different contexts with two distinctive estimating values. In the case of digital devices, the bandwidth is measured in bits per second ( bits per second ) or bytes per irregular. In the sheath of analogue devices, the bandwidth is measured in cycles per second, or Hertz ( Hz ). Bandwidth is only one part of what an individual sees as the rush of a net. on-key internet travel rapidly is actually the come of data you receive every second and that has a distribute to do with rotational latency besides.

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