Computer networking MCQ

941. When a host on network A sends a message to a host on network B, which address does the router look at?

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

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Moderate

Concept notes: When a host on network A sends a message to a host on network B, the router uses the logical (IP) address to determine the destination network.

Common Mistakes: Students often confuse the logical address with the physical (MAC) address, which is used for communication within the same network segment.

Explanations: Routers operate at the network layer of the OSI model, where they use IP addresses to forward packets between different networks. The logical address, or IP address, is crucial for routing decisions. Physical addresses (MAC addresses) are used for communication within the same network segment and are not used by routers to make routing decisions.

Option Analysis:

Option A: Port numbers are used at the transport layer and are not used by routers for routing decisions.
Option B: Logical addresses (IP addresses) are used by routers to determine the destination network.
Option C: Physical addresses (MAC addresses) are used for communication within the same network segment and are not used by routers for routing decisions.
Option D: This option is incorrect as the logical address is the correct answer.

Mnemonic: IP for Inter-Network Path

942. ..... allow insertion and extraction of signals.

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

Exam Relevance: GATE, IEEE, CCNA

Difficulty: Moderate

Concept notes: ADM stands for Add-Drop Multiplexer, which is a device used in telecommunications networks to add or drop specific signals from a larger data stream.

Common Mistakes: Students may confuse ADMs with regenerators, which are used to amplify and clean up signals, not to add or drop them.

Explanations: ADM devices are specifically designed to allow the insertion and extraction of signals from a larger data stream. This capability is crucial for managing traffic in telecommunications networks, enabling the addition or removal of specific signals as needed. Regenerators and STS multiplexer/demultiplexers do not have this specific function.

Option Analysis:

Option A: Regenerators are used to amplify and clean up signals, not to add or drop them.
Option B: ADMs are designed to add or drop specific signals from a larger data stream, making them the correct choice.
Option C: STS multiplexer/demultiplexers combine or separate signals but do not specifically add or drop them.
Option D: This option is incorrect as ADMs are the correct answer.

Mnemonic: ADM: Add-Drop Multiplexer

943. Which layer 4 protocol is used for a Telnet connection?

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

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: Telnet is a protocol used for remote terminal connection over a network. It operates at the application layer and uses TCP for reliable data transmission at the transport layer.

Common Mistakes: Students may confuse Telnet with other protocols like UDP, which is used for unreliable, connectionless communication.

Explanations: Telnet uses TCP because it requires a reliable connection to ensure that all data packets are delivered in the correct order. TCP provides error-checking and flow control, which are essential for a protocol like Telnet that needs to maintain a stable and consistent connection.

Option Analysis:

Option A: IP is a network layer protocol and does not provide the necessary reliability for Telnet.
Option B: TCP is the correct choice as it provides the reliable, connection-oriented service required by Telnet.
Option C: TCP/IP is a suite of protocols, not a single protocol, and is not the correct answer for the specific layer 4 protocol used by Telnet.
Option D: UDP is a connectionless protocol and does not provide the reliability needed for Telnet.

Mnemonic: TCP for Telnet, Connection is Key.

944. You want to improve network performance by increasing the bandwidth available to hosts and limit the size of the broadcast domains. Which of the following options will achieve this goal?

Correct Answer: Correct answer is: (D) Switches configured with VLANs.

Exam Relevance: CCNA, CompTIA Network+, Cisco Certified Network Associate

Difficulty: Moderate

Concept notes: Switches configured with VLANs can increase bandwidth available to hosts and limit the size of broadcast domains.

Common Mistakes: Students may mistakenly believe that switches alone can achieve both goals without VLANs.

Explanations: Switches increase bandwidth by providing dedicated bandwidth to each connected device, thus reducing collisions and improving network performance. VLANs further enhance this by segmenting the network into smaller broadcast domains, which reduces broadcast traffic and improves overall network efficiency. Therefore, switches configured with VLANs achieve both goals of increasing bandwidth and limiting broadcast domain size.

Option Analysis:

Option A: Managed hubs do not increase bandwidth or limit broadcast domains effectively.
Option B: Bridges can limit broadcast domains but do not increase bandwidth significantly.
Option C: Switches alone increase bandwidth but do not limit broadcast domains as effectively as VLANs.
Option D: Switches configured with VLANs both increase bandwidth and limit broadcast domains.

945. Which of the following is not a digital-to-analog conversion?

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

Exam Relevance: GATE, ECE, EE, DSP

Difficulty: Moderate

Concept notes: Analog-to-digital conversion involves converting analog signals into digital form, while digital-to-analog conversion involves converting digital signals into analog form. AM (Amplitude Modulation) is an analog modulation technique, not a digital-to-analog conversion method.

Common Mistakes: Students may confuse AM with digital modulation techniques like ASK, PSK, and FSK, which are used in digital-to-analog conversion.

Explanations: AM (Amplitude Modulation) is an analog modulation technique where the amplitude of a carrier wave is varied in accordance with the information signal. It is not a digital-to-analog conversion method. In contrast, ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), and FSK (Frequency Shift Keying) are digital modulation techniques used to convert digital signals into analog form, making them digital-to-analog conversion methods.

Option Analysis:

Option A: ASK is a digital-to-analog conversion method where the amplitude of a carrier wave is varied to represent digital data.
Option B: PSK is a digital-to-analog conversion method where the phase of a carrier wave is varied to represent digital data.
Option C: FSK is a digital-to-analog conversion method where the frequency of a carrier wave is varied to represent digital data.
Option D: AM is an analog modulation technique, not a digital-to-analog conversion method.

946. Three methods of switching are

Correct Answer: Correct answer is: (B) Circuit switching, packet switching, and message switching.

Exam Relevance: Networking exams, Telecommunications exams, Computer Science exams

Difficulty: Easy

Concept notes: The three primary methods of switching in telecommunications are circuit switching, packet switching, and message switching.

Common Mistakes: Students may confuse protocol switching with circuit switching, as both involve the establishment of a connection, but protocol switching is not a distinct switching method.

Explanations: Circuit switching establishes a dedicated path for communication between two points, packet switching breaks data into packets and routes them independently, and message switching sends entire messages as a whole. These three methods are fundamental to understanding data transmission in telecommunications.

Option Analysis:

Option A: Protocol switching is not a distinct switching method and is not one of the primary methods.
Option B: Correctly identifies the three primary switching methods.
Option C: Loop switching is not a recognized switching method in telecommunications.
Option D: Node switching is not a recognized switching method in telecommunications.

Mnemonic: Circuit, Packet, Message (CPM)

947. Total length field defines total length of datagram including the

Correct Answer: Correct answer is: (C) Header.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Moderate

Concept notes: The total length field in a datagram specifies the entire length of the datagram, including the header.

Common Mistakes: Students often confuse the total length field with just the data length, not realizing it includes the header.

Explanations: The total length field in a datagram includes the header because the header contains essential information about the datagram, such as source and destination addresses, protocol type, and other control information. Therefore, the total length must account for the header to accurately represent the entire datagram.

Option Analysis:

Option A: Length is a general term and does not specify what part of the datagram is included.
Option B: Data Length refers only to the payload and does not include the header.
Option C: Header is the correct choice as the total length includes the header.
Option D: Footer is not a standard part of a datagram and is not included in the total length.

948. Which of the IP headers decides when the packet should bediscarded?

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

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Moderate

Concept notes: The Time to Live (TTL) field in the IP header determines how long a packet can exist in the network before it is discarded.

Common Mistakes: Students often confuse the TTL field with the Checksum field, which is used for error detection rather than packet lifetime.

Explanations: The TTL field in the IP header is decremented by each router that forwards the packet. When the TTL reaches zero, the packet is discarded to prevent infinite looping in the network. This ensures that packets do not remain in the network indefinitely.

Option Analysis:

Option A: The Checksum field is used for error detection in the header, not for determining when a packet should be discarded.
Option B: The Header field is a general term and does not specifically determine when a packet should be discarded.
Option C: The CRC (Cyclic Redundancy Check) is used for error detection in data links, not in the IP header.
Option D: The TTL field is the correct choice as it determines the packet's lifetime and when it should be discarded.

Mnemonic: Think "TTL: Time to Live, Time to Leave."

949. In Ethernet addressing, if the least significant bit of the first byte is 0, the address is.....

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

Exam Relevance: CCNA, CompTIA Network+, CISSP

Difficulty: Easy

Concept notes: In Ethernet addressing, the least significant bit of the first byte determines whether the address is unicast, multicast, or broadcast.

Common Mistakes: Students often confuse the bit position and its meaning, leading to incorrect identification of address types.

Explanations: In Ethernet addressing, if the least significant bit of the first byte is 0, the address is unicast. This is because a unicast address is used for one-to-one communication, and the least significant bit being 0 indicates that the address is intended for a single device.

Option Analysis:

Option A: Correct. The least significant bit being 0 indicates a unicast address.
Option B: Incorrect. A multicast address has the least significant bit of the first byte set to 1.
Option C: Incorrect. A broadcast address is a special case of multicast where all bits are 1.
Option D: Incorrect. The correct answer is provided in the options.

Mnemonic: 0 for One (Unicast)

950. Shift cipheris sometimes referred to as the

Correct Answer: Correct answer is: (A) Caesar cipher.

Exam Relevance: Cryptography exams, Information Security exams, Computer Science exams

Difficulty: Easy

Concept notes: The shift cipher is a type of substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet. It is often referred to as the Caesar cipher because it was reportedly used by Julius Caesar.

Common Mistakes: Students may confuse the shift cipher with other types of ciphers, such as the Vigenère cipher or the substitution cipher, which are more complex.

Explanations: The shift cipher is sometimes referred to as the Caesar cipher because it was historically used by Julius Caesar to encrypt military messages. This cipher involves shifting each letter in the plaintext by a fixed number of positions in the alphabet. The term "Caesar cipher" is widely recognized and used in cryptography literature to describe this specific type of shift cipher.

Option Analysis:

Option A: Correct. The shift cipher is often called the Caesar cipher due to its historical use by Julius Caesar.
Option B: Incorrect. There is no widely recognized "Julia cipher" in cryptography.
Option C: Incorrect. "Plain cipher" is not a recognized term in cryptography.
Option D: Incorrect. Only the Caesar cipher is a correct alternative name for the shift cipher.

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Computer networking MCQ - Set 95

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