Computer networking MCQ – Change your future

81. 3 base band systems use..... encoding.

Correct Answer: Correct answer is: (A) Manchester.

Exam Relevance: GATE, ECE, EE

Difficulty: Moderate

Concept notes: Manchester encoding is a line code in which the encoding of each data bit is either low then high or high then low, ensuring a transition at the middle of each bit period.

Common Mistakes: Students often confuse Manchester encoding with other encoding schemes like NRZ or RZ, which do not guarantee a transition in the middle of each bit period.

Explanations: Manchester encoding is used in base band systems because it ensures a transition in the middle of each bit period, which helps in clock recovery and reduces the DC component. This makes it suitable for base band systems where clock recovery is crucial.

Option Analysis:

Option A: Manchester encoding is correct because it ensures a transition in the middle of each bit period, which is beneficial for base band systems.
Option B: RZ (Return to Zero) encoding does not guarantee a transition in the middle of each bit period, making it less suitable for base band systems.
Option C: NRZ (Non-Return to Zero) encoding does not have a guaranteed transition in the middle of each bit period, making it less suitable for base band systems.
Option D: RZ or NRZ encoding does not guarantee a transition in the middle of each bit period, making it less suitable for base band systems.

Mnemonic: Mnemonic: "Manchester Moves Midway"

82. In classless addressing, the..... is another name for the common part of the address range.

Correct Answer: Correct answer is: (B) Prefix.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: In classless addressing, the common part of the address range is known as the prefix.

Common Mistakes: Students may confuse the prefix with the suffix, which is not relevant in this context.

Explanations: In classless addressing, the prefix is the part of the IP address that is common to a group of addresses. It is used to identify the network portion of the address. The prefix is crucial for routing and subnetting in modern IP addressing schemes.

Option Analysis:

Option A: Suffix is incorrect because it refers to the end part of a word or address, not the common part of an address range.
Option B: Prefix is correct as it refers to the common part of the address range in classless addressing.
Option C: Netid is incorrect as it is not a standard term used in classless addressing to describe the common part of the address range.
Option D: None of the above is incorrect because the correct term, prefix, is listed as an option.

Mnemonic: Prefix = Pre-common

83. Which of the following commands will configure all the default VTY ports on a router?

Correct Answer: Correct answer is: (B) Router (config) #line vty 0 4.

Exam Relevance: CCNA, Network+

Difficulty: Moderate

Concept notes: The command to configure VTY lines on a router is entered in global configuration mode. The range 0 to 4 covers all default VTY ports.

Common Mistakes: Students may confuse the command with the console line configuration or may not be aware that the range 0 to 4 is used to configure all default VTY ports.

Explanations: The command "Router (config) #line vty 0 4" is used to configure all the default VTY ports on a router. This command is entered in global configuration mode, indicated by the "(config)" prompt. The range "0 4" specifies the range of VTY lines to be configured, which includes all the default VTY ports (0 through 4). This is the correct command to configure all VTY ports for remote access.

Option Analysis:

Option A: This command is missing the "(config)" prompt, indicating it is not in the correct mode to configure VTY lines.
Option B: This command is correct as it is in global configuration mode and specifies the correct range for all default VTY ports.
Option C: This command configures the console line, not the VTY lines.
Option D: The "all" keyword is not valid for configuring VTY lines; the correct range is "0 4".

84. Managed by one person or organization from a single device.

Correct Answer: Correct answer is: (A) PAN.

Exam Relevance: CCNA, CompTIA Network+, CIW Network Specialist

Difficulty: Easy

Concept notes: A Personal Area Network (PAN) is a network for interconnecting devices in close proximity to an individual, typically within a range of a few meters. It is managed by one person or organization from a single device.

Common Mistakes: Students may confuse PAN with LAN, as both are network types. However, LANs are typically larger and cover a broader area, such as a home or office, and are not limited to a single user.

Explanations: A Personal Area Network (PAN) is designed to interconnect devices within a small area, usually within a few meters, and is managed by one person or organization from a single device. This makes it distinct from other network types like LAN, MAN, and WAN, which cover larger areas and involve multiple users or devices.

Option Analysis:

Option A: Correct. A PAN is managed by one person or organization from a single device.
Option B: Incorrect. A Local Area Network (LAN) covers a larger area and involves multiple devices and users.
Option C: Incorrect. A Metropolitan Area Network (MAN) covers a city or large campus and involves multiple users and devices.
Option D: Incorrect. A Wide Area Network (WAN) covers a large geographical area and involves multiple users and devices.

Mnemonic: PAN: Personal Area Network, Personal, Private, Proximity.

85. Field that is used to detect errors over entire user datagram is called

Correct Answer: Correct answer is: (A) Checksum.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Easy

Concept notes: Checksum is a field used in the User Datagram Protocol (UDP) to detect errors in the entire datagram.

Common Mistakes: Students may confuse checksum with other error detection methods like parity checks or cyclic redundancy checks (CRC).

Explanations: Checksum is a simple error detection mechanism used in UDP. It is calculated over the entire datagram, including the header and data. The receiver recalculates the checksum and compares it with the one received. If they do not match, an error is detected.

Option Analysis:

Option A: Correct. Checksum is used to detect errors in the entire datagram.
Option B: Incorrect. Error Detection Protocol is not a specific field in UDP.
Option C: Incorrect. Source-Error Removal is not a standard term in UDP.
Option D: Incorrect. Datagram-Error Removal is not a standard term in UDP.

86. ..... is a dynamic mapping protocol in which a physical address is found for a given logical address.

Correct Answer: Correct answer is: (A) ARP.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: ARP (Address Resolution Protocol) is a protocol used to map IP addresses to physical (MAC) addresses on a local network.

Common Mistakes: Students may confuse ARP with RARP, which maps physical addresses to IP addresses, rather than the other way around.

Explanations: ARP is a dynamic mapping protocol that finds the physical (MAC) address for a given logical (IP) address. This is essential for communication between devices on a local network. RARP, on the other hand, does the reverse mapping, which is not the focus of the question.

Option Analysis:

Option A: ARP is correct as it maps IP addresses to MAC addresses.
Option B: RARP maps MAC addresses to IP addresses, which is the opposite of what is described in the question.
Option C: Both ARP and RARP are not correct because the question specifies a protocol that maps IP to MAC, not both ways.
Option D: None of the above is incorrect because ARP is the correct protocol for the described function.

Mnemonic: ARP: Address Resolution Protocol

87. IGMP is..... protocol.

Correct Answer: Correct answer is: (B) A group management.

Exam Relevance: CCNA, CCNP, CISSP

Difficulty: Easy

Concept notes: IGMP (Internet Group Management Protocol) is used for managing multicast groups in IP networks.

Common Mistakes: Students may confuse IGMP with ICMP (Internet Control Message Protocol), which is used for error reporting.

Explanations: IGMP is a protocol used to manage multicast groups in IP networks. It allows hosts to join or leave multicast groups and enables routers to track which hosts are interested in receiving multicast traffic. This makes it a group management protocol, not an error reporting, transmission, or other type of protocol.

Option Analysis:

Option A: IGMP is not an error reporting protocol. ICMP is used for error reporting.
Option B: IGMP is used for managing multicast groups, making it a group management protocol.
Option C: IGMP is not a transmission protocol. It is used for managing multicast groups.
Option D: The correct answer is provided, so this option is incorrect.

88. Consider the following Statements: A wired network uses cables to connect devices, such as laptop or desktop computers, to the Internet or another network. Synchronous is without a clock. Fibre Optic Cables are faster than Ethernet cables Which of the following statement(s) is/are true?

Correct Answer: Correct answer is: (D) Only 1, 3.

Exam Relevance: CCNA, CompTIA Network+, CISSP

Difficulty: Moderate

Concept notes: A wired network uses cables to connect devices to the Internet or another network. Fibre optic cables are faster than Ethernet cables. Synchronous communication requires a clock signal.

Common Mistakes: Students may incorrectly believe that synchronous communication does not require a clock signal, leading them to think statement 2 is true.

Explanations: Statement 1 is true because wired networks indeed use cables to connect devices to the Internet or another network. Statement 2 is false because synchronous communication requires a clock signal to synchronize data transmission. Statement 3 is true because fibre optic cables transmit data at higher speeds compared to Ethernet cables.

Option Analysis:

Option A: Incorrect because statement 2 is false.
Option B: Incorrect because statement 2 is false.
Option C: Incorrect because statement 2 is false.
Option D: Correct because statements 1 and 3 are true.

Mnemonic: Wired Networks, Clocks, Fiber Speed

89. A file is being transferred. The time required actually is 6-hours. The mean time between crashes is 2-hours. The time required for the transfer is hours if synchronization is not provided.

Correct Answer: Correct answer is: (D) Infinite.

Exam Relevance: Computer Science, Software Engineering, Systems Reliability

Difficulty: Hard

Concept notes: The concept revolves around the reliability of a file transfer process in the presence of crashes. If the mean time between crashes is less than the required transfer time, the transfer cannot be completed without synchronization.

Common Mistakes: Students might incorrectly assume that the transfer can be completed in a finite time, ignoring the impact of repeated crashes.

Explanations: The file transfer requires 6 hours to complete. However, the mean time between crashes is only 2 hours. This implies that the system is likely to crash before the transfer is completed. Each crash resets the transfer process, leading to an infinite loop of crashes and restarts. Therefore, without synchronization to handle crashes, the transfer cannot be completed in a finite time, making the answer infinite.

Option Analysis:

Option A: 12 hours is incorrect because the crashes will prevent the transfer from completing in any finite time.
Option B: 3 hours is incorrect because the crashes will prevent the transfer from completing in any finite time.
Option C: Zero hours is incorrect because the transfer cannot be completed instantly, and crashes will prevent any progress.
Option D: Infinite is correct because the crashes will prevent the transfer from ever completing.

90. IP Security operates in which layer of the OSI model?

Correct Answer: Correct answer is: (A) Network.

Exam Relevance: CISSP, CCNA, CompTIA Security+

Difficulty: Easy

Concept notes: IP Security (IPsec) operates at the network layer of the OSI model, which is layer 3.

Common Mistakes: Students may confuse IPsec with other security protocols that operate at different layers, such as SSL/TLS which operates at the transport layer.

Explanations: IPsec is designed to provide secure communication over IP networks. It operates at the network layer, ensuring that data packets are encrypted and authenticated as they travel across the network. This layer is responsible for routing and addressing, making it an ideal location for implementing security measures that protect the integrity and confidentiality of data packets.

Option Analysis:

Option A: Correct. IPsec operates at the network layer.
Option B: Incorrect. The transport layer is where protocols like TCP and UDP operate, not IPsec.
Option C: Incorrect. The application layer is where user applications interact with the network, not where IPsec operates.
Option D: Incorrect. The physical layer deals with the transmission and reception of raw bit streams over a physical medium, not with security protocols.

Mnemonic: N for Network, N for NetSec (IPsec)

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Computer networking MCQ - Set 9

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