Q1. Which statement best describes the primary purpose of a computer network?
A. To eliminate the need for operating systems
B. To enable communication and resource sharing between devices
C. To ensure every computer has the same IP address
D. To prevent all unauthorized access automatically
Answer: B
Solution: A computer network connects devices to exchange data and share resources such as files, printers, applications, and internet connections.
Q2. Which network topology provides a dedicated point-to-point link between every pair of devices?
A. Bus
B. Ring
C. Full mesh
D. Star
Answer: C
Solution: A full mesh with \(n\) devices requires \(n(n-1)/2\) links. It provides high redundancy but is expensive to implement.
Q3. A network contains 12 devices connected using a full-mesh topology. How many point-to-point links are required?
A. 24
B. 66
C. 72
D. 132
Answer: B
Solution:
Q4. Which topology has a single central device whose failure can disconnect all attached nodes?
A. Star
B. Mesh
C. Ring with bypass links
D. Fully connected topology
Answer: A
Solution: In a star topology, every node depends on the central hub or switch for communication with other nodes.
Q5. Which network type generally covers a geographical area larger than a LAN but smaller than a WAN?
A. PAN
B. MAN
C. SAN
D. BAN
Answer: B
Solution: A Metropolitan Area Network (MAN) typically connects networks across a city or metropolitan region.
Q6. Which of the following is not a standard network performance criterion?
A. Throughput
B. Delay
C. Reliability
D. File extension
Answer: D
Solution: Network criteria include performance, reliability, and security. File extensions identify file formats rather than network quality.
Q7. Which device primarily regenerates a weakened signal at the physical layer?
A. Router
B. Repeater
C. Application gateway
D. Proxy server
Answer: B
Solution: A repeater regenerates or retimes signals to extend transmission distance. It does not normally make routing decisions.
Q8. Which device normally forwards Ethernet frames using a MAC address table?
A. Layer 2 switch
B. Repeater
C. Modem only
D. Passive hub
Answer: A
Solution: A Layer 2 switch learns source MAC addresses and forwards frames through the appropriate switch ports.
Q9. Which statement about a bridge is correct?
A. It operates exclusively at the application layer.
B. It forwards frames based on IP addresses only.
C. It connects LAN segments and filters frames using MAC addresses.
D. It translates domain names into IP addresses.
Answer: C
Solution: A traditional bridge is a Layer 2 device that learns MAC addresses and filters or forwards Ethernet frames.
Q10. Which device is primarily responsible for forwarding packets between different IP networks?
A. Hub
B. Router
C. Repeater
D. Passive splitter
Answer: B
Solution: Routers examine network-layer addressing and consult routing tables to select a next hop.
Q11. What is the main difference between a hub and a switch?
A. A hub forwards only IP packets.
B. A switch forwards frames selectively using MAC addresses.
C. A switch cannot connect multiple devices.
D. A hub performs dynamic routing.
Answer: B
Solution: A hub repeats incoming signals to its ports, whereas a switch normally forwards a frame only to the relevant destination port, except for flooding cases.
Q12. Which device commonly separates broadcast domains by default?
A. Layer 2 hub
B. Layer 2 switch without VLAN separation
C. Router
D. Repeater
Answer: C
Solution: Routers do not forward ordinary Layer 2 broadcasts between interfaces. VLANs also create separate broadcast domains on switches.
Q13. In a conventional Ethernet LAN, what does a collision domain represent?
A. A group of devices sharing a DNS server
B. A network area in which simultaneous transmissions may collide
C. All devices having the same subnet mask
D. A group of routers running OSPF
Answer: B
Solution: Collision domains are relevant to shared media and half-duplex Ethernet. Full-duplex switched Ethernet links normally avoid collisions.
Q14. Which statement about a VLAN is correct?
A. It creates logical Layer 2 network segmentation.
B. It replaces the need for MAC addresses.
C. It guarantees encryption of all traffic.
D. It is always equivalent to a physical cable.
Answer: A
Solution: VLANs logically separate Layer 2 broadcast domains. Communication between different VLANs generally requires Layer 3 routing.
Q15. What is the primary purpose of a default gateway on a host?
A. To assign a MAC address to the host
B. To forward traffic destined for other IP networks
C. To encrypt every outgoing packet
D. To resolve all URLs into domain names
Answer: B
Solution: The default gateway is the next-hop router used when the destination is outside the host's directly connected network.
Q16. Which topology has the characteristic that a break in a simple, unidirectional ring can interrupt the entire ring?
A. Star
B. Bus
C. Ring
D. Full mesh
Answer: C
Solution: A basic ring depends on a continuous path. Dual-ring or self-healing designs can provide additional resilience.
Q17. What is the main purpose of a network protocol?
A. To specify rules for communication between systems
B. To increase CPU clock speed
C. To replace all network hardware
D. To guarantee unlimited bandwidth
Answer: A
Solution: Protocols define communication rules such as message formats, addressing, sequencing, error handling, and connection management.
Q18. Which is an example of a connection-oriented transport protocol?
A. UDP
B. TCP
C. ARP
D. ICMP
Answer: B
Solution: TCP establishes a logical connection and provides ordered, reliable byte-stream delivery. UDP does not establish a transport connection.
Q19. Which network architecture separates service providers from service consumers?
A. Client-server
B. Bus topology
C. Ring topology
D. Half-duplex transmission
Answer: A
Solution: In a client-server model, clients request resources or services from servers. Peer-to-peer systems instead allow nodes to act as both providers and consumers.
Q20. A network designer needs high availability and multiple alternative paths between devices. Which topology is generally most suitable?
A. Single bus
B. Simple ring
C. Full or partial mesh
D. Single-hub star without redundancy
Answer: C
Solution: Mesh networks offer alternate paths when links fail. A partial mesh often provides a practical balance between redundancy and cost.
Q21. Which OSI layer is responsible for routing packets between networks?
A. Physical
B. Data Link
C. Network
D. Presentation
Answer: C
Solution: The Network layer, Layer 3, handles logical addressing and routing. IP is its best-known protocol.
Q22. Which OSI layer is primarily responsible for framing and MAC addressing?
A. Data Link
B. Network
C. Session
D. Application
Answer: A
Solution: Layer 2 frames network-layer packets, uses MAC addressing where applicable, and can provide link-level error detection.
Q23. At which OSI layer does TCP operate?
A. Network
B. Transport
C. Session
D. Data Link
Answer: B
Solution: TCP operates at the Transport layer and provides reliable, ordered byte-stream communication.
Q24. Which OSI layer is most closely associated with data compression, format translation, and encryption as conceptual functions?
A. Physical
B. Presentation
C. Network
D. Data Link
Answer: B
Solution: The Presentation layer, Layer 6, represents data-format and transformation functions in the OSI model. Real-world protocols may distribute these functions across several layers.
Q25. Which layer establishes, manages, and terminates sessions in the conceptual OSI model?
A. Session
B. Physical
C. Network
D. Data Link
Answer: A
Solution: The Session layer is Layer 5. Its conceptual responsibilities include dialog management and synchronization.
Q26. What is the correct order of OSI layers from lowest to highest?
A. Physical, Network, Data Link, Transport, Session, Presentation, Application
B. Physical, Data Link, Network, Transport, Session, Presentation, Application
C. Data Link, Physical, Network, Session, Transport, Application, Presentation
D. Network, Physical, Data Link, Transport, Presentation, Session, Application
Answer: B
Solution: The seven layers are Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Q27. Which layer handles the transmission of raw bits over a physical medium?
A. Physical
B. Network
C. Transport
D. Application
Answer: A
Solution: The Physical layer defines signaling, physical interfaces, bit transmission, and related electrical, optical, or radio characteristics.
Q28. Which statement about TCP/IP and OSI models is correct?
A. Both models must have exactly seven layers.
B. TCP/IP has no application layer.
C. TCP/IP's Internet layer broadly corresponds to the OSI Network layer.
D. TCP operates at the OSI Network layer.
Answer: C
Solution: The TCP/IP Internet layer handles IP addressing and packet routing, corresponding broadly to OSI Layer 3.
Q29. Which protocol maps an IPv4 address to a local network's hardware address?
A. DNS
B. ARP
C. DHCP
D. SMTP
Answer: B
Solution: Address Resolution Protocol (ARP) discovers the link-layer address associated with an IPv4 address on a local link.
Q30. What does a router typically do to the IPv4 TTL field when forwarding a packet?
A. Increases it by one
B. Decreases it by one
C. Replaces it with the destination port
D. Removes the field
Answer: B
Solution: Each IPv4 router decreases TTL by at least one. If TTL reaches zero, the packet is discarded and an ICMP Time Exceeded message may be returned.
Q31. Which protocol is used to report errors and provide diagnostic information at the IP layer?
A. ICMP
B. FTP
C. SMTP
D. SNMP
Answer: A
Solution: ICMP carries control and diagnostic messages, such as Echo Request/Reply and Destination Unreachable.
Q32. Which service translates a domain name such as example.com into an IP address?
A. DHCP
B. DNS
C. ARP
D. NTP
Answer: B
Solution: DNS uses distributed, hierarchical records to resolve domain names and provide other naming-related information.
Q33. Which protocol dynamically provides IP configuration to network hosts?
A. DHCP
B. HTTP
C. SSH
D. IMAP
Answer: A
Solution: DHCP can supply an IP address, subnet mask, default gateway, DNS servers, and lease information.
Q34. Which protocol is designed to synchronize clocks across networked systems?
A. FTP
B. NTP
C. ARP
D. POP3
Answer: B
Solution: Network Time Protocol (NTP) synchronizes system clocks using timing exchanges and clock-offset calculations.
Q35. Which device is most directly associated with converting signals between transmission technologies or media?
A. Modem
B. DNS resolver
C. Application server
D. Firewall rule
Answer: A
Solution: A modem modulates and demodulates signals to enable communication over a particular transmission system, such as certain cable or DSL links.
Q36. What is the principal function of a proxy server?
A. It must always act as a physical repeater.
B. It intermediates requests between clients and other servers.
C. It replaces all IP routing.
D. It guarantees that all websites are safe.
Answer: B
Solution: A proxy can filter requests, cache content, enforce access policies, or hide internal client addresses from external services, depending on its configuration.
Q37. Which technology commonly allows several VLANs to share one switch-to-switch link?
A. Access port
B. 802.1Q trunking
C. ARP poisoning
D. NAT loopback
Answer: B
Solution: IEEE 802.1Q adds VLAN tags to Ethernet frames on trunk links, enabling multiple VLANs to traverse the same physical connection.
Q38. What is the main function of the Spanning Tree Protocol (STP)?
A. Encrypt Ethernet frames
B. Prevent Layer 2 switching loops
C. Resolve domain names
D. Assign dynamic IP addresses
Answer: B
Solution: STP blocks selected redundant Layer 2 paths to create a loop-free logical topology while retaining backup links.
Q39. Which protocol securely supports remote command-line administration?
A. Telnet
B. FTP
C. SSH
D. HTTP
Answer: C
Solution: SSH provides encrypted remote login and can also support tunneling and secure file transfer. Telnet does not encrypt traffic by default.
Q40. Which protocol is used to retrieve email while allowing messages to remain synchronized across multiple devices?
A. IMAP
B. ARP
C. RIP
D. ICMP
Answer: A
Solution: IMAP supports server-side mailbox access and synchronization. POP3 is traditionally oriented toward downloading messages, although modern clients may retain copies.
Q41. What is the Nyquist maximum bit rate for a noiseless channel with bandwidth \(B\) and \(L\) discrete signal levels?
A. \(B\log_2 L\)
B. \(2B\log_2 L\)
C. \(B/L\)
D. \(2B/L\)
Answer: B
Solution: The Nyquist formula is \(R_{\max}=2B\log_2 L\) bits per second for the idealized noiseless-channel model.
Q42. According to Shannon's capacity theorem, which expression gives the capacity of a band-limited noisy channel?
A. \(B\log_2(1+S/N)\)
B. \(2B(S/N)\)
C. \(B/(S+N)\)
D. \(S\log_2 B\)
Answer: A
Solution: Shannon capacity is \(C=B\log_2(1+S/N)\), where \(S/N\) is the linear signal-to-noise power ratio.
Q43. A channel has a bandwidth of 3 kHz and a signal-to-noise ratio of 31. What is its Shannon capacity?
A. 3 kbps
B. 9 kbps
C. 15 kbps
D. 30 kbps
Answer: B
Solution: Since \(1+31=32\) and \(\log_2 32=5\), capacity is \(3000\times5=15{,}000\) bps. Therefore, the correct capacity is 15 kbps, option C.
Q44. A digital signal uses 8 distinct signal levels. How many bits can each signal element represent?
A. 2
B. 3
C. 4
D. 8
Answer: B
Solution: Bits per signal element are \(\log_2 L=\log_2 8=3\).
Q45. Which transmission medium generally offers the greatest bandwidth and immunity to electromagnetic interference over long distances?
A. Unshielded twisted pair
B. Coaxial cable
C. Optical fiber
D. Infrared through open air
Answer: C
Solution: Optical fiber carries information using light and is highly resistant to electromagnetic interference. Its practical capacity depends on the fiber, optics, and transmission system.
Q46. Which of the following is a guided transmission medium?
A. Microwave
B. Satellite radio
C. Optical fiber
D. Infrared through free space
Answer: C
Solution: Guided media constrain signals to a physical path, such as twisted-pair cable, coaxial cable, or optical fiber.
Q47. Which multiplexing technique assigns different frequency bands to different signals?
A. TDM
B. FDM
C. CDM only
D. Statistical addressing
Answer: B
Solution: Frequency Division Multiplexing (FDM) allocates separate frequency ranges to multiple signals sharing a medium.
Q48. In Time Division Multiplexing (TDM), how are multiple signals commonly separated?
A. By different time slots
B. By different MAC addresses only
C. By different cable colors
D. By changing the IP version
Answer: A
Solution: TDM allocates transmission opportunities in separate time slots. Synchronous TDM reserves recurring slots, while statistical TDM assigns them dynamically.
Q49. Which switching technique establishes a dedicated communication path for the duration of a connection?
A. Packet switching
B. Circuit switching
C. Datagram switching without reservation
D. Store-and-forward routing only
Answer: B
Solution: Circuit switching reserves a path or circuit for the session, potentially providing predictable resources but wasting capacity during idle periods.
Q50. Which switching technique divides data into packets that may independently traverse different routes?
A. Circuit switching
B. Datagram packet switching
C. Dedicated leased circuit only
D. Analog frequency division only
Answer: B
Solution: In a datagram network, each packet is forwarded independently and may follow a different route to the destination.
Q51. What is the principal difference between baseband and broadband transmission in traditional networking terminology?
A. Baseband uses digital signaling over the medium, while broadband often uses modulated frequency channels.
B. Baseband always requires satellite communication.
C. Broadband cannot carry multiple channels.
D. Baseband is necessarily wireless.
Answer: A
Solution: In traditional LAN terminology, baseband transmits a signal directly over the medium, while broadband commonly divides capacity into modulated frequency channels.
Q52. What does the bit rate measure?
A. Number of bytes stored on disk
B. Number of bits transmitted per second
C. Number of routers in a network
D. Number of signal levels only
Answer: B
Solution: Bit rate is measured in bits per second (bps). Baud rate measures signal symbols per second, which is not necessarily equal to bit rate.
Q53. A modem transmits 2,400 symbols per second, each representing 4 bits. What is the gross bit rate?
A. 600 bps
B. 2,400 bps
C. 4,800 bps
D. 9,600 bps
Answer: D
Solution: Bit rate = symbol rate × bits per symbol = \(2400\times4=9600\) bps, ignoring coding overhead.
Q54. Which Ethernet standard supports 1 Gbps over four pairs of Category 5e or better copper cabling?
A. 10BASE-T
B. 100BASE-TX
C. 1000BASE-T
D. 10GBASE-SR
Answer: C
Solution: 1000BASE-T supports Gigabit Ethernet over four twisted pairs, typically up to 100 meters on suitable cabling.
Q55. What is the nominal data rate of Fast Ethernet?
A. 10 Mbps
B. 100 Mbps
C. 1 Gbps
D. 10 Gbps
Answer: B
Solution: Fast Ethernet typically refers to IEEE 802.3u Ethernet operating at 100 Mbps.
Q56. Which statement about full-duplex Ethernet is correct?
A. It requires CSMA/CD to resolve collisions.
B. It allows simultaneous transmission and reception on a link without normal Ethernet collisions.
C. It always uses a shared coaxial bus.
D. It prevents frame loss under all conditions.
Answer: B
Solution: Full-duplex switched Ethernet permits simultaneous bidirectional transmission. CSMA/CD is associated with shared, half-duplex Ethernet.
Q57. What is the primary function of an Ethernet frame's Frame Check Sequence (FCS)?
A. Correct every corrupted bit
B. Detect frame corruption using a CRC
C. Encrypt the payload
D. Resolve the destination IP address
Answer: B
Solution: Ethernet's FCS uses a cyclic redundancy check to detect many transmission errors. It does not normally correct the corrupted frame.
Q58. Which transmission mode allows communication in both directions, but not simultaneously?
A. Simplex
B. Half-duplex
C. Full-duplex
D. Multiplexed simplex only
Answer: B
Solution: Half-duplex communication permits both parties to transmit, but they take turns. Full-duplex supports simultaneous transmission in both directions.
Q59. Which statement about satellite communication is correct?
A. It is always free from propagation delay.
B. Geostationary satellite links can have significant propagation delay.
C. It requires a physical copper cable between every endpoint.
D. It cannot support broadcasting.
Answer: B
Solution: Geostationary satellites orbit roughly 35,786 km above the equator, producing substantial round-trip propagation delay.
Q60. Which wireless technology is commonly used for short-range, low-power personal-area communication?
A. Bluetooth
B. SONET
C. 1000BASE-T
D. Frame Relay
Answer: A
Solution: Bluetooth is widely used for short-range connections among peripherals, phones, wearables, and embedded devices.
Q61. Which technique detects transmission errors by appending a polynomial remainder to a data frame?
A. DNS
B. CRC
C. NAT
D. DHCP
Answer: B
Solution: Cyclic Redundancy Check (CRC) treats data as a polynomial over GF(2) and appends a calculated remainder. The receiver checks the resulting codeword for errors.
Q62. A parity bit is added to a data word using even parity. Which condition must hold?
A. The number of 1s in the complete word must be even.
B. The number of 0s must be odd.
C. The data must contain exactly one 1.
D. The parity bit must always be zero.
Answer: A
Solution: Even parity makes the total number of 1s, including the parity bit, even. Simple parity cannot detect every possible multiple-bit error.
Q63. Which error-detection method can detect all odd numbers of bit errors?
A. Single parity bit
B. Plain checksum in every possible case
C. Repetition without comparison
D. Data compression
Answer: A
Solution: A single parity bit detects any odd number of bit flips because the parity changes. It can miss errors involving an even number of flipped bits.
Q64. What is the minimum Hamming distance required for a code to detect up to \(s\) bit errors?
A. \(s\)
B. \(s+1\)
C. \(2s+1\)
D. \(2s\)
Answer: B
Solution: A code with minimum distance \(d_{\min}\) detects up to \(d_{\min}-1\) errors, so detection of \(s\) errors requires \(d_{\min}\geq s+1\).
Q65. What minimum Hamming distance is required to correct up to 3 bit errors?
A. 3
B. 4
C. 6
D. 7
Answer: D
Solution: Correcting \(t\) errors requires \(d_{\min}\geq2t+1\). For \(t=3\), the minimum distance is 7.
Q66. In Stop-and-Wait ARQ, what does the sender normally do after transmitting a frame?
A. Transmit every remaining frame immediately
B. Wait for an acknowledgment or timeout before proceeding
C. Disable error detection
D. Change its IP address
Answer: B
Solution: Stop-and-Wait ARQ sends one outstanding frame at a time. A timeout or negative acknowledgment can trigger retransmission.
Q67. In Go-Back-N ARQ with a \(k\)-bit sequence number, what is the maximum sender window size?
A. \(2^k\)
B. \(2^k-1\)
C. \(2^{k-1}\)
D. \(k-1\)
Answer: B
Solution: Go-Back-N uses a sender window of at most \(2^k-1\) frames to avoid ambiguity when sequence numbers wrap around.
Q68. For a \(k\)-bit sequence number, what is the maximum window size in Selective Repeat ARQ under the standard rule?
A. \(2^k\)
B. \(2^k-1\)
C. \(2^{k-1}\)
D. \(2k\)
Answer: C
Solution: Selective Repeat limits the sender and receiver windows to at most half the sequence-number space, \(2^{k-1}\), preventing old and new frames from being confused.
Q69. Which ARQ method retransmits only the specific missing or damaged frames?
A. Stop-and-Wait without retransmission
B. Go-Back-N
C. Selective Repeat
D. Circuit switching
Answer: C
Solution: Selective Repeat buffers correctly received out-of-order frames and retransmits only frames that need recovery.
Q70. What is the purpose of byte stuffing in a data-link protocol?
A. To increase IP address length
B. To distinguish data bytes from special framing bytes
C. To assign VLAN identifiers
D. To calculate a routing metric
Answer: B
Solution: Byte stuffing inserts escape bytes when payload data contains reserved delimiter values, preventing the receiver from misinterpreting data as frame boundaries.
Q71. Bit stuffing in a flag-based framing protocol commonly inserts a 0 after how many consecutive 1s in the data?
A. 3
B. 5
C. 7
D. 8
Answer: B
Solution: In protocols such as HDLC, a 0 is inserted after five consecutive 1s in the transmitted data to prevent accidental appearance of the flag pattern.
Q72. Which protocol is associated with traditional point-to-point link framing and negotiation?
A. PPP
B. DNS
C. OSPF
D. SMTP
Answer: A
Solution: Point-to-Point Protocol (PPP) supports framing, link configuration through LCP, and optional network-layer configuration through NCPs.
Q73. What is the main purpose of CSMA/CD?
A. Collision avoidance in modern Wi-Fi
B. Collision detection on shared, half-duplex Ethernet
C. Routing between autonomous systems
D. Encryption of wireless traffic
Answer: B
Solution: Carrier Sense Multiple Access with Collision Detection detects collisions on shared Ethernet media, then applies a backoff procedure. Modern switched full-duplex Ethernet does not use it.
Q74. Which mechanism is associated with traditional Wi-Fi medium access?
A. CSMA/CD
B. CSMA/CA
C. BGP
D. Token Ring routing
Answer: B
Solution: CSMA/CA attempts to reduce collisions by sensing the medium and using contention procedures. Wireless stations cannot reliably detect collisions in the same way as classic shared Ethernet.
Q75. What is the purpose of the binary exponential backoff algorithm in Ethernet?
A. To choose increasingly spaced random retransmission delays after collisions
B. To encrypt packets using increasing key sizes
C. To select a DNS root server
D. To assign a subnet mask
Answer: A
Solution: After a collision, a station chooses a random backoff interval from an expanding range, reducing the likelihood of repeated simultaneous retransmissions.
Q76. Which statement about the MAC sublayer is correct?
A. It is part of the Data Link layer.
B. It replaces the Transport layer.
C. It handles only application encryption.
D. It is responsible for global IP routing.
Answer: A
Solution: The Data Link layer is often divided into MAC and LLC sublayers. MAC handles media access and link-layer addressing in technologies such as Ethernet.
Q77. What is the principal purpose of a sliding-window protocol?
A. To eliminate the need for acknowledgments in all cases
B. To allow multiple frames to be outstanding and improve link utilization
C. To replace all error detection
D. To route packets between autonomous systems
Answer: B
Solution: Sliding-window protocols pipeline transmission by allowing multiple unacknowledged frames, reducing the idle time associated with Stop-and-Wait.
Q78. Which protocol is commonly used to prevent persistent loops in a redundant switched Ethernet topology?
A. STP
B. FTP
C. POP3
D. SNMP
Answer: A
Solution: Spanning Tree Protocol disables selected redundant Layer 2 paths, preventing frames from circulating indefinitely in switching loops.
Q79. Which IEEE standard specifies VLAN tagging commonly used on Ethernet trunk links?
A. IEEE 802.1Q
B. IEEE 802.11ax
C. IEEE 802.3u
D. IEEE 802.15.4
Answer: A
Solution: IEEE 802.1Q specifies VLAN tagging and related bridging mechanisms used to carry VLAN information across trunk links.
Q80. Which statement best distinguishes flow control from congestion control?
A. Flow control protects the receiver; congestion control addresses overload in the network.
B. Both exclusively detect physical cable faults.
C. Congestion control is only used by DNS.
D. Flow control always increases the receiver's buffer size.
Answer: A
Solution: Flow control prevents a sender from overwhelming a receiver. Congestion control aims to avoid or respond to excessive traffic load in the network.
Q81. How many bits are in an IPv4 address?
A. 16
B. 32
C. 48
D. 128
Answer: B
Solution: IPv4 addresses contain 32 bits and are commonly written as four decimal octets.
Q82. How many bits are in an IPv6 address?
A. 32
B. 48
C. 64
D. 128
Answer: D
Solution: IPv6 uses 128-bit addresses, providing a much larger address space than IPv4.
Q83. Which of the following is a private IPv4 address?
A. 8.8.8.8
B. 172.20.5.4
C. 200.1.1.1
D. 1.1.1.1
Answer: B
Solution: The private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
Q84. What is the subnet mask for the prefix /26?
A. 255.255.255.0
B. 255.255.255.128
C. 255.255.255.192
D. 255.255.255.224
Answer: C
Solution: A /26 mask contains 26 network bits: 255.255.255.192.
Q85. How many usable host addresses are available in a conventional IPv4 /27 subnet?
A. 14
B. 30
C. 32
D. 62
Answer: B
Solution: There are \(2^{32-27}=32\) total addresses. In a conventional subnet, subtract the network and broadcast addresses, leaving 30 usable hosts.
Q86. Which is the correct network address for 192.168.10.77/26?
A. 192.168.10.0
B. 192.168.10.64
C. 192.168.10.77
D. 192.168.10.128
Answer: B
Solution: A /26 subnet has blocks of 64 addresses. The ranges begin at .0, .64, .128, and .192; address .77 belongs to the .64 subnet.
Q87. What is the broadcast address of the subnet 192.168.1.64/26?
A. 192.168.1.95
B. 192.168.1.126
C. 192.168.1.127
D. 192.168.1.128
Answer: C
Solution: The subnet spans .64 through .127. Therefore, .127 is the broadcast address and .65 through .126 are the conventional usable host addresses.
Q88. A network needs at least 50 conventional usable IPv4 host addresses per subnet. Which prefix is the most specific suitable choice?
A. /27
B. /26
C. /28
D. /29
Answer: B
Solution: A /26 offers 62 usable addresses. A /27 offers only 30, so /26 is the smallest suitable subnet among these choices.
Q89. What is the primary benefit of CIDR compared with classful addressing?
A. It eliminates the need for routers.
B. It allows flexible prefix lengths and more efficient address allocation.
C. It requires all networks to use /8.
D. It converts IPv4 directly into MAC addresses.
Answer: B
Solution: Classless Inter-Domain Routing uses variable-length prefixes, supports route aggregation, and reduces the limitations of fixed class A, B, and C network boundaries.
Q90. What does NAT commonly do in a residential IPv4 router?
A. Translate between private and public IP address information
B. Convert every TCP packet into UDP
C. Replace DNS with ARP
D. Encrypt all Ethernet frames
Answer: A
Solution: Network Address Translation rewrites IP address information and, in common port-address translation configurations, transport ports as well.
Q91. Which IPv4 address is the loopback address commonly used for local testing?
A. 0.0.0.0
B. 127.0.0.1
C. 169.254.1.1
D. 255.255.255.255
Answer: B
Solution: The 127.0.0.0/8 block is reserved for IPv4 loopback. The address 127.0.0.1 commonly identifies the local host.
Q92. What does an IPv4 address beginning with 169.254 commonly indicate on a host configured for automatic private addressing?
A. A multicast destination
B. A link-local address, often assigned when DHCP configuration fails
C. A global IPv6 address
D. A DNS root server
Answer: B
Solution: IPv4 link-local addresses use the 169.254.0.0/16 block. They support local-link communication but generally do not provide normal internet connectivity.
Q93. Which IPv6 address type is used for communication with the nearest member of a group according to routing distance?
A. Anycast
B. Broadcast
C. IPv4 loopback
D. Ethernet multicast only
Answer: A
Solution: IPv6 supports unicast, multicast, and anycast. Anycast assigns the same address to multiple interfaces and routes traffic to one selected, typically nearest, destination. IPv6 does not use broadcast addresses.
Q94. Which IPv6 address is the loopback address?
A. ::
B. ::1
C. FF00::
D. FE80::
Answer: B
Solution: ::1 is the IPv6 loopback address. :: is the unspecified address, FF00::/8 is multicast space, and FE80::/10 is link-local space.
Q95. What is the main function of ARP in an IPv4 LAN?
A. Determine a local-link MAC address corresponding to an IPv4 next-hop address
B. Find a website's TLS certificate
C. Choose the best BGP autonomous system path
D. Negotiate TCP window scaling
Answer: A
Solution: ARP resolves an IPv4 next-hop address to a link-layer address on the local network. For remote destinations, the host typically resolves the gateway's MAC address.
Q96. Which protocol replaces ARP's neighbor-discovery role in IPv6?
A. ICMPv6 Neighbor Discovery
B. FTP
C. RIP version 1
D. SMTP
Answer: A
Solution: IPv6 uses Neighbor Discovery Protocol (NDP), based on ICMPv6, for functions including neighbor address resolution and router discovery.
Q97. Which field in the IPv4 header identifies the upper-layer protocol carried in the packet?
A. TTL
B. Protocol
C. Header Checksum
D. Identification
Answer: B
Solution: The IPv4 Protocol field identifies the payload protocol, such as TCP (6), UDP (17), or ICMP (1).
Q98. What is the purpose of the IPv4 Identification field in conventional fragmentation and reassembly?
A. To identify a group of fragments belonging to the same original datagram
B. To specify the TCP destination port
C. To encode the router's MAC address
D. To select a DNS resolver
Answer: A
Solution: The Identification field helps receivers associate fragments with the original datagram. Fragment offsets and flags provide additional fragmentation information.
Q99. Which statement about IPv4 fragmentation is correct?
A. Every router must fragment every packet.
B. IPv4 routers may fragment packets when permitted and required by the outgoing link MTU.
C. TCP port numbers control IP fragmentation.
D. IPv6 routers perform ordinary in-path fragmentation.
Answer: B
Solution: IPv4 fragmentation depends on packet size, outgoing MTU, and the Don't Fragment flag. IPv6 routers do not fragment packets in transit; the source may use a Fragment header.
Q100. A host sends a packet to an address outside its subnet. What destination MAC address is normally used on the first Ethernet hop?
A. The remote server's MAC address
B. The default gateway's MAC address
C. The DNS server's MAC address in all cases
D. The broadcast MAC address for every packet
Answer: B
Solution: The Ethernet frame is addressed to the local next-hop router. The IP destination remains the remote host's IP address unless a mechanism such as NAT modifies it.
Q101. Which routing algorithm is traditionally associated with the Bellman–Ford approach?
A. Link-state routing
B. Distance-vector routing
C. Spanning Tree Protocol
D. Ethernet switching
Answer: B
Solution: Distance-vector protocols calculate routes using information exchanged with neighboring routers. RIP is a classic example.
Q102. Which algorithm is commonly used by link-state routing protocols to calculate shortest paths?
A. Dijkstra's algorithm
B. Round-robin scheduling
C. Binary search
D. CRC calculation
Answer: A
Solution: Link-state routers construct a topology database and run Dijkstra's shortest-path-first algorithm to determine best paths.
Q103. Which protocol is an interior gateway protocol that uses link-state routing?
A. BGP
B. OSPF
C. HTTP
D. ARP
Answer: B
Solution: Open Shortest Path First (OSPF) is a link-state Interior Gateway Protocol (IGP) used within an autonomous system.
Q104. Which routing protocol uses hop count as its primary routing metric?
A. RIP
B. OSPF
C. BGP
D. IS-IS exclusively
Answer: A
Solution: RIP uses hop count, with 15 as the maximum usable hop count and 16 representing an unreachable destination.
Q105. Which routing protocol is primarily used to exchange routing information between autonomous systems on the internet?
A. RIP
B. OSPF
C. BGP
D. ARP
Answer: C
Solution: Border Gateway Protocol (BGP) is the principal interdomain routing protocol and uses path attributes and policy to select routes.
Q106. What is the count-to-infinity problem associated with?
A. Distance-vector routing
B. DNS recursion
C. TCP connection termination
D. Optical multiplexing
Answer: A
Solution: Routers may gradually increase a route's metric while mistakenly believing a failed destination remains reachable through one another. Split horizon, poison reverse, and triggered updates can help mitigate the problem.
Q107. What is the main purpose of split horizon in distance-vector routing?
A. Prevent a router from advertising a route back through the interface on which it was learned
B. Encrypt routing updates
C. Reduce the IPv4 header to 20 bytes
D. Replace the routing table with a DNS cache
Answer: A
Solution: Split horizon reduces routing loops by suppressing advertisements of a route back toward the neighbor from which that route was learned.
Q108. Which statement about administrative distance is correct in common Cisco routing implementations?
A. It measures physical cable length in meters.
B. It compares the trustworthiness of route sources.
C. It is the same as an OSPF link cost.
D. It is an IPv4 header field.
Answer: B
Solution: Administrative distance ranks the preference of route sources on a Cisco device. Lower values are generally preferred when comparing competing routes to the same destination prefix.
Q109. Which route is normally selected first by longest-prefix matching?
A. A matching /16 route over a matching /24 route
B. A matching /24 route over a matching /16 route
C. The route with the highest next-hop IP address
D. The route with the oldest timestamp in every implementation
Answer: B
Solution: Routers prefer the most specific matching prefix. Route-source preference and metrics determine which route is installed among competing candidates for the same prefix.
Q110. Which routing metric is used by classic RIP?
A. Delay only
B. Hop count
C. Bandwidth only
D. Autonomous system number
Answer: B
Solution: RIP uses hop count and regards 16 hops as unreachable. It does not directly calculate path quality using bandwidth or delay.
Q111. Which statement about OSPF areas is correct?
A. Area 0 is the backbone area in conventional multi-area OSPF design.
B. Every OSPF router must be in a separate autonomous system.
C. OSPF uses DNS names instead of IP prefixes.
D. OSPF is an application-layer file-transfer protocol.
Answer: A
Solution: Area 0 provides the backbone for inter-area routing in conventional OSPF designs. Area boundaries help limit link-state information and organize routing.
Q112. Which statement best describes BGP path selection?
A. It always chooses the route with the fewest physical cables.
B. It uses path attributes and routing policy, with selection details depending on implementation and configuration.
C. It selects routes solely by Ethernet MAC address.
D. It always uses Dijkstra's algorithm.
Answer: B
Solution: BGP evaluates attributes such as local preference, AS-path length, origin, MED, and other tie-breakers according to its decision process and configuration.
Q113. What is an autonomous system in internet routing?
A. A collection of routers and networks under a common routing administration and policy
B. A single Ethernet frame
C. A DNS resource record
D. A device with no IP address
Answer: A
Solution: An Autonomous System (AS) is a set of IP networks operated under a common administrative routing policy and identified externally by an AS number.
Q114. Which of the following is a path-vector routing protocol?
A. BGP
B. Classic Ethernet
C. ARP
D. CSMA/CD
Answer: A
Solution: BGP advertises reachability information along with AS-path and other attributes, supporting interdomain routing and loop prevention.
Q115. In a distance-vector algorithm, a router learns route information primarily from:
A. Its neighbors' routing advertisements
B. The destination's physical keyboard
C. The DNS root zone only
D. TCP acknowledgments only
Answer: A
Solution: Each router shares distance and reachability information with neighbors and uses it to calculate routes.
Q116. What is the principal purpose of route aggregation?
A. Increase the number of routing-table entries
B. Advertise a summarized prefix covering multiple more-specific networks
C. Replace every subnet with a MAC address
D. Force all packets through a single router
Answer: B
Solution: Route summarization combines contiguous prefixes where appropriate, reducing routing-table size and advertisement overhead.
Q117. Which routing approach is most directly associated with routers maintaining a view of network topology?
A. Link-state routing
B. Pure flooding without topology information
C. Static Ethernet learning only
D. DNS caching
Answer: A
Solution: Link-state protocols distribute link-state information, build a topology database, and calculate shortest paths from that database.
Q118. What is the purpose of a routing table's next-hop field?
A. Identify the next router or forwarding target toward the destination
B. Store the application's password
C. Determine the source file's extension
D. Specify the TCP payload length
Answer: A
Solution: A route's next hop identifies where a packet should be forwarded. A directly connected route may instead specify the outgoing interface without a separate next-hop router.
Q119. What does equal-cost multipath routing (ECMP) enable?
A. Forwarding traffic over multiple paths with equal routing cost
B. Using multiple destination IP addresses in one IPv4 header
C. Disabling all routing protocols
D. Converting TCP into Ethernet
Answer: A
Solution: ECMP permits multiple equal-cost forwarding paths. Traffic distribution depends on implementation and may use per-flow hashing to reduce packet reordering.
Q120. Which technique can be used to discover the sequence of routers along an IP path?
A. Traceroute
B. SMTP
C. IMAP
D. MIME
Answer: A
Solution: Traceroute commonly sends probes with increasing TTL or hop-limit values and interprets responses from intermediate routers to infer the path.
Q121. What is the principal difference between TCP and UDP?
A. TCP provides reliable, ordered byte-stream delivery; UDP provides datagrams without built-in delivery guarantees.
B. UDP always encrypts data.
C. TCP cannot use port numbers.
D. UDP always establishes a three-way handshake.
Answer: A
Solution: TCP supports sequencing, acknowledgment, retransmission, and flow and congestion control. UDP provides a lightweight datagram service.
Q122. What is the correct order of the TCP three-way handshake?
A. ACK, SYN, FIN
B. SYN, SYN-ACK, ACK
C. FIN, FIN-ACK, SYN
D. SYN-ACK, FIN, ACK
Answer: B
Solution: The client sends SYN, the server responds with SYN-ACK, and the client completes the handshake with ACK.
Q123. Which TCP field identifies the next byte expected by the receiver in an acknowledgment?
A. Window size
B. Acknowledgment number
C. Urgent pointer only
D. Header checksum
Answer: B
Solution: TCP acknowledgments generally identify the next sequence number expected, enabling cumulative acknowledgment of received bytes.
Q124. What is the primary purpose of the TCP receive window?
A. Advertise how much additional data the receiver can accept
B. Specify the router's administrative distance
C. Identify a DNS record
D. Replace the TCP sequence number
Answer: A
Solution: The advertised receive window supports receiver-side flow control. TCP congestion control separately regulates the sender's load on the network.
Q125. Which TCP mechanism helps prevent a sender from overwhelming a receiver?
A. Flow control
B. DNS recursion
C. ARP caching
D. VLAN tagging
Answer: A
Solution: TCP flow control uses the advertised receive window to constrain outstanding data according to the receiver's available buffer capacity.
Q126. Which TCP mechanism primarily helps prevent excessive traffic from overwhelming the network?
A. Congestion control
B. MAC address learning
C. MIME encoding
D. DNS caching
Answer: A
Solution: TCP congestion-control algorithms adjust the sending rate in response to network conditions, including congestion signals and packet loss.
Q127. Which TCP flag is commonly used to initiate connection establishment?
A. FIN
B. SYN
C. RST
D. PSH
Answer: B
Solution: SYN synchronizes sequence numbers during connection establishment.
Q128. Which TCP flag is commonly associated with orderly connection termination?
A. SYN
B. FIN
C. URG
D. ECE only
Answer: B
Solution: FIN indicates that a sender has finished sending data in one direction. TCP connections are full-duplex, so each direction can be closed independently.
Q129. Why does TCP commonly use a four-segment exchange for connection termination?
A. Both directions may be closed independently, and acknowledgments are needed.
B. Every connection requires four DNS queries.
C. TCP cannot acknowledge FIN.
D. Every packet must contain four IP headers.
Answer: A
Solution: A typical termination uses FIN, ACK, FIN, ACK, though segments may be combined and real-world sequences can differ.
Q130. What is the purpose of TCP retransmission?
A. Recover data believed to have been lost or not acknowledged
B. Assign a new MAC address to every router
C. Change a hostname into an IP address
D. Encrypt a file using a public key
Answer: A
Solution: TCP uses retransmission timers and, where applicable, duplicate-acknowledgment or other loss-detection mechanisms to recover missing data.
Q131. What is the main reason for TCP's TIME-WAIT state?
A. Allow delayed duplicate segments to expire and help ensure the final acknowledgment can be retransmitted
B. Resolve all DNS entries
C. Reserve a permanent IP address
D. Disable the receiver's flow control
Answer: A
Solution: TIME-WAIT helps protect subsequent connections from delayed segments belonging to an earlier connection and allows retransmission of the final ACK if needed.
Q132. Which of the following is the default port for HTTPS?
A. TCP 21
B. TCP 25
C. TCP 80
D. TCP 443
Answer: D
Solution: HTTPS conventionally uses TCP port 443. HTTP/3 uses QUIC over UDP, normally on port 443.
Q133. Which port is conventionally used by DNS for queries?
A. 22
B. 53
C. 110
D. 143
Answer: B
Solution: DNS commonly uses UDP port 53 for ordinary queries and TCP port 53 for cases including zone transfers and responses that require TCP. DNS can also operate over encrypted transports.
Q134. Which protocol normally uses UDP port 123?
A. NTP
B. HTTPS
C. SSH
D. FTP
Answer: A
Solution: NTP commonly uses UDP port 123 to synchronize clocks across networked devices.
Q135. Which protocol conventionally uses TCP port 22?
A. Telnet
B. SSH
C. SMTP
D. DHCP
Answer: B
Solution: SSH uses TCP port 22 by default for secure remote access and related functions.
Q136. Which statement about UDP is correct?
A. UDP guarantees in-order delivery.
B. UDP has no built-in retransmission or connection-establishment handshake.
C. UDP cannot use port numbers.
D. UDP always performs congestion control in the same manner as TCP.
Answer: B
Solution: UDP preserves message boundaries but does not itself guarantee delivery, ordering, or duplicate suppression.
Q137. Which transport protocol is used by QUIC?
A. UDP
B. ICMP
C. ARP
D. Ethernet FCS
Answer: A
Solution: QUIC runs over UDP and provides features including secure connection establishment, multiplexed streams, and loss recovery. HTTP/3 uses QUIC.
Q138. What does MSS mean in TCP?
A. Maximum Segment Size
B. Minimum Switching Speed
C. Main Subnet Service
D. Maximum Server Sessions
Answer: A
Solution: MSS is the maximum TCP payload size carried in one segment, excluding TCP and IP headers. It is commonly derived from the path MTU and header sizes.
Q139. An Ethernet path has an MTU of 1500 bytes. Assume a 20-byte IPv4 header and a 20-byte TCP header, with no options. What is the maximum TCP MSS for this path?
A. 1400 bytes
B. 1460 bytes
C. 1480 bytes
D. 1500 bytes
Answer: B
Solution: MSS = MTU − IPv4 header − TCP header = \(1500-20-20=1460\) bytes.
Q140. Which protocol is particularly suitable for latency-sensitive applications that can tolerate some packet loss or implement their own recovery?
A. UDP
B. ARP
C. STP
D. ICMP only
Answer: A
Solution: UDP's low overhead and lack of built-in retransmission can suit real-time audio, video, gaming, and custom transports. Application requirements determine whether it is appropriate.
Q141. Which DNS record type maps a hostname to an IPv4 address?
A. AAAA
B. A
C. MX
D. PTR
Answer: B
Solution: An A record maps a name to an IPv4 address. AAAA records map names to IPv6 addresses.
Q142. Which DNS record identifies mail servers responsible for receiving email for a domain?
A. MX
B. TXT only
C. CNAME only
D. SOA only
Answer: A
Solution: MX records identify mail exchangers and include preference values used to order candidate servers.
Q143. Which protocol is commonly used to send email between mail servers?
A. SMTP
B. POP3
C. ARP
D. ICMP
Answer: A
Solution: Simple Mail Transfer Protocol (SMTP) is used to relay and submit email. IMAP and POP3 are used for mailbox access.
Q144. Which protocol is traditionally associated with retrieving email by downloading messages from a mailbox server?
A. POP3
B. OSPF
C. SNMP
D. PPP
Answer: A
Solution: POP3 retrieves email from a server. IMAP provides richer mailbox synchronization, folders, and server-side message management.
Q145. Which protocol is primarily used to monitor and manage network devices through management information and operations?
A. SNMP
B. FTP
C. SMTP
D. HTTP only
Answer: A
Solution: Simple Network Management Protocol supports monitoring and management. SNMP managers query agents, and agents can send notifications such as traps or informs.
Q146. Which HTTP status code indicates that the request succeeded but the server has no response content to return?
A. 200
B. 204
C. 301
D. 404
Answer: B
Solution: HTTP 204 No Content indicates successful processing without a response body.
Q147. Which HTTP status code normally indicates that authentication is required or has failed?
A. 201
B. 302
C. 401
D. 503
Answer: C
Solution: HTTP 401 indicates missing or invalid authentication credentials and generally includes a WWW-Authenticate challenge when applicable. HTTP 403 indicates that the server refuses the request.
Q148. What does HTTP status code 404 indicate?
A. The request was successfully created.
B. The requested resource was not found, or the server is unwilling to disclose that it exists.
C. The server is permanently redirecting the request.
D. The request was accepted for asynchronous processing.
Answer: B
Solution: HTTP 404 Not Found is used when the requested resource cannot be found or the server does not disclose it.
Q149. Which HTTP status code indicates that the server encountered an unexpected condition that prevented it from fulfilling a request?
A. 200
B. 301
C. 403
D. 500
Answer: D
Solution: HTTP 500 Internal Server Error is a generic server-side error response.
Q150. What is the main security difference between HTTP and HTTPS?
A. HTTPS uses TLS to protect HTTP communication in transit.
B. HTTPS eliminates the need for authentication in every application.
C. HTTP always uses UDP, while HTTPS always uses TCP.
D. HTTPS prevents all application vulnerabilities.
Answer: A
Solution: HTTPS protects HTTP traffic using TLS, providing encryption, integrity, and server authentication when certificate validation succeeds. It does not guarantee that a website or its content is trustworthy.
Q151. Which FTP mode initiates the data connection from the server to the client?
A. Passive mode
B. Active mode
C. DNS mode
D. SMTP mode
Answer: B
Solution: In traditional active FTP, the client establishes the control connection and tells the server where to connect for data. In passive FTP, the client initiates the data connection to a server-selected port.
Q152. Which protocol provides secure file transfer and remote file operations over an SSH connection?
A. SFTP
B. TFTP
C. Telnet
D. ARP
Answer: A
Solution: SSH File Transfer Protocol (SFTP) is distinct from FTP. It transfers and manages files over SSH.
Q153. What is the primary role of MIME in email and related internet messaging?
A. Define support for content types and representations beyond plain ASCII text
B. Assign IP addresses to routers
C. Replace TCP sequence numbers
D. Prevent every email phishing attempt
Answer: A
Solution: Multipurpose Internet Mail Extensions describes content types and encodings, allowing email to carry attachments, images, and other media.
Q154. Which protocol is commonly used to transfer web pages and API requests?
A. HTTP
B. RIP
C. STP
D. ARP
Answer: A
Solution: HTTP is an application-layer protocol used by browsers, web servers, and many APIs.
Q155. What is the main purpose of a URI?
A. Identify a resource by name, location, or another identifier
B. Assign a physical MAC address
C. Calculate an Ethernet checksum
D. Establish a TCP handshake
Answer: A
Solution: A Uniform Resource Identifier identifies a resource. A URL is a type of URI that specifies how or where a resource can be located.
Q156. Which protocol commonly provides encrypted communication for remote shell access?
A. Telnet
B. SSH
C. TFTP
D. HTTP without TLS
Answer: B
Solution: SSH provides secure remote login, command execution, and tunneling. Telnet sends data, including credentials, without encryption by default.
Q157. Which application protocol is commonly used to distribute device configuration to a client without manually entering an IP address?
A. DHCP
B. IMAP
C. BGP
D. MIME
Answer: A
Solution: DHCP provides dynamic network configuration, including addresses and other parameters. Automatic Private IP Addressing is a different mechanism that may be used when IPv4 DHCP configuration fails.
Q158. Which protocol is designed for lightweight publish-subscribe messaging and is widely used in IoT?
A. MQTT
B. FTP
C. OSPF
D. ARP
Answer: A
Solution: MQTT uses a broker-based publish-subscribe model, allowing publishers and subscribers to communicate through topics with relatively low protocol overhead.
Q159. Which statement about Telnet is correct?
A. It is an encrypted replacement for TLS.
B. It provides remote terminal access but does not encrypt traffic by default.
C. It is the primary IPv6 neighbor-discovery protocol.
D. It is a link-state routing protocol.
Answer: B
Solution: Telnet commonly uses TCP port 23 and is insecure for untrusted networks because credentials and data can be transmitted in plaintext.
Q160. Which protocol is commonly used to synchronize user mailboxes across multiple devices while keeping folder and message state on the server?
A. IMAP
B. ARP
C. ICMP
D. RIP
Answer: A
Solution: IMAP supports server-side folders, message flags, and synchronization across devices.
Q161. Which security property ensures that data has not been modified without authorization?
A. Confidentiality
B. Integrity
C. Availability
D. Scalability
Answer: B
Solution: Integrity protects against unauthorized alteration. Cryptographic hashes combined with a secure MAC or digital signature can help verify integrity and authenticity.
Q162. Which cryptographic technique uses the same secret key for encryption and decryption?
A. Symmetric-key cryptography
B. Asymmetric-key cryptography
C. Digital signatures alone
D. Public-key certificates alone
Answer: A
Solution: Symmetric cryptography uses a shared secret key. AES is a widely used symmetric encryption algorithm.
Q163. Which cryptographic approach uses a mathematically related public key and private key?
A. Symmetric encryption only
B. Asymmetric cryptography
C. Plaintext substitution without keys
D. CRC
Answer: B
Solution: Public-key cryptography uses a key pair. Depending on the algorithm, it can support encryption, key establishment, or digital signatures.
Q164. What does a digital signature primarily provide?
A. Confidentiality without any other mechanism
B. Origin authentication and integrity, with support for non-repudiation under appropriate conditions
C. Guaranteed prevention of all malware
D. Automatic compression of network packets
Answer: B
Solution: A digital signature binds a signed message to a private-key holder and enables integrity verification. Real-world non-repudiation also depends on identity verification, key security, and legal and operational context.
Q165. Which statement correctly describes a cryptographic hash?
A. It is designed to be a fixed-length digest of input data.
B. It must always be reversible.
C. It is the same as an IP address.
D. It automatically provides confidentiality.
Answer: A
Solution: Cryptographic hashes such as SHA-256 produce fixed-length digests. A hash alone does not encrypt data or authenticate the sender.
Q166. Which protocol suite is commonly used to secure IP traffic at the network layer?
A. IPsec
B. FTP
C. POP3
D. MIME
Answer: A
Solution: IPsec supports IP-layer security using protocols and mechanisms including Authentication Header (AH) and Encapsulating Security Payload (ESP).
Q167. What is the primary purpose of TLS?
A. Protect data exchanged between communicating endpoints
B. Replace all routing protocols
C. Assign MAC addresses dynamically
D. Eliminate the need for certificates in every deployment
Answer: A
Solution: Transport Layer Security protects data in transit through encryption, integrity protection, and authentication, depending on the configuration.
Q168. What is the main difference between IDS and IPS?
A. IDS is generally used to detect suspicious activity; IPS can also block or prevent it inline.
B. IDS assigns IP addresses; IPS translates domain names.
C. IDS encrypts data; IPS compresses it.
D. They are both exclusively physical-layer devices.
Answer: A
Solution: An Intrusion Detection System generates alerts or records suspicious activity. An Intrusion Prevention System can take enforcement actions, such as dropping malicious traffic.
Q169. What is the primary purpose of a firewall access control list (ACL)?
A. Define traffic-matching rules that permit or deny specified traffic
B. Increase the length of IPv6 addresses
C. Generate TCP sequence numbers
D. Convert analog signals to digital signals
Answer: A
Solution: ACLs filter traffic according to configured criteria such as source and destination addresses, protocols, and ports.
Q170. Which authentication protocol is commonly associated with centralized network access control and AAA?
A. RADIUS
B. ARP
C. STP
D. FTP
Answer: A
Solution: RADIUS supports authentication, authorization, and accounting for network access. TACACS+ is another AAA-related protocol, often used for administrative access to network devices.
Q171. What does AAA stand for in network security?
A. Authentication, Authorization, and Accounting
B. Addressing, Allocation, and ARP
C. Application, Automation, and Access
D. Authentication, Addressing, and Availability
Answer: A
Solution: Authentication verifies identity, authorization determines permitted actions, and accounting records usage or activity.
Q172. What is the main purpose of Kerberos?
A. Provide ticket-based network authentication
B. Route IP packets using link-state advertisements
C. Detect Ethernet frame errors
D. Translate IPv4 addresses into MAC addresses
Answer: A
Solution: Kerberos uses tickets and a trusted Key Distribution Center to authenticate entities without transmitting the user's password directly to every service.
Q173. What is the primary purpose of a public-key certificate?
A. Bind an identity or subject to a public key through a trusted issuer's signature
B. Replace the public key with a MAC address
C. Guarantee that the certificate holder's website is harmless
D. Store every user's private key in plaintext
Answer: A
Solution: Certificates, commonly X.509, bind a subject's identity to a public key. Trust depends on certificate validation, the issuing chain, and the intended use.
Q174. What is the main security benefit of multi-factor authentication (MFA)?
A. It requires multiple authentication factors from distinct categories.
B. It always requires three passwords.
C. It eliminates every phishing risk.
D. It replaces all authorization checks.
Answer: A
Solution: MFA combines different factor categories, such as knowledge, possession, and inherence. Two passwords alone do not constitute two distinct factors.
Q175. What is a man-in-the-middle attack?
A. An attacker secretly intercepts or alters communication between parties.
B. A router selects the shortest path.
C. A switch learns a source MAC address.
D. A DNS server caches a valid response.
Answer: A
Solution: A man-in-the-middle attacker positions themselves between communicating parties, potentially intercepting or modifying messages. Strong authentication and properly validated TLS can help prevent such attacks.
Q176. What is the primary goal of a denial-of-service attack?
A. Make a service or resource unavailable to legitimate users
B. Improve route aggregation
C. Increase encryption strength
D. Synchronize network clocks
Answer: A
Solution: DoS attacks exhaust or disrupt a service's resources. Distributed denial-of-service attacks use multiple sources to increase the impact.
Q177. Which statement about WPA3-Personal is correct?
A. It uses SAE authentication instead of the WPA2-Personal PSK handshake method.
B. It eliminates the need for encryption.
C. It is an Ethernet routing protocol.
D. It requires WEP to be enabled.
Answer: A
Solution: WPA3-Personal uses Simultaneous Authentication of Equals (SAE), strengthening password-based authentication compared with the traditional WPA2-Personal PSK approach.
Q178. What is the primary purpose of a Hardware Security Module (HSM)?
A. Securely generate, store, and use cryptographic keys
B. Replace all network switches
C. Provide a DNS zone transfer
D. Assign private IP addresses to all hosts
Answer: A
Solution: HSMs are specialized devices that protect cryptographic keys and perform sensitive cryptographic operations within a controlled hardware environment.
Q179. What is the purpose of role-based access control (RBAC)?
A. Grant permissions based on assigned roles
B. Grant every user unrestricted administrator access
C. Select routes by hop count
D. Detect errors using parity bits
Answer: A
Solution: RBAC assigns permissions to roles and associates users with those roles, helping enforce least privilege and simplify access management.
Q180. Which practice most directly protects passwords against offline cracking after a database breach?
A. Store passwords in plaintext
B. Use a unique salt and a suitable password-hashing algorithm such as Argon2id
C. Encrypt every password with a publicly shared key
D. Store passwords in a browser cookie without protection
Answer: B
Solution: Salted, deliberately expensive password hashing makes large-scale offline guessing more costly. Strong passwords, appropriate parameters, and secure credential handling remain important.
Q181. What is Software-Defined Networking (SDN) primarily intended to achieve?
A. Separate network control logic from packet-forwarding functions
B. Eliminate the need for network protocols
C. Replace IP addresses with passwords
D. Prevent all hardware failures
Answer: A
Solution: SDN separates the control plane from the data plane conceptually, enabling programmable network management and centralized or logically centralized control.
Q182. What is Network Function Virtualization (NFV)?
A. Implementing network functions using software on virtualized or general-purpose infrastructure
B. Replacing all network communication with virtual reality
C. A technique for calculating CRC values
D. A physical-layer error-correction code
Answer: A
Solution: NFV virtualizes functions such as firewalls, load balancers, and routers so that they can run as software rather than requiring dedicated appliances for each function.
Q183. What is a virtual switch in a virtualized environment?
A. Software that forwards traffic between virtual interfaces and, depending on design, physical network interfaces
B. A device that performs only DNS lookups
C. A replacement for all host operating systems
D. A protocol for sending email attachments
Answer: A
Solution: A virtual switch provides Layer 2 connectivity between virtual machines, containers, or host interfaces, often with VLAN and policy support.
Q184. Which technology allows multiple virtual routing tables to operate independently on the same physical router?
A. VRF
B. MIME
C. ARQ
D. CRC
Answer: A
Solution: Virtual Routing and Forwarding (VRF) maintains separate routing and forwarding instances, supporting network segmentation and overlapping address spaces.
Q185. Which wireless technology is specifically associated with low-power mesh networking in many IoT deployments?
A. Zigbee
B. SONET
C. 100BASE-TX
D. Frame Relay
Answer: A
Solution: Zigbee uses IEEE 802.15.4-based low-power wireless networking and supports mesh networking in suitable device roles and deployments.
Q186. What is the principal difference between Wi-Fi and Li-Fi?
A. Wi-Fi uses radio-frequency communication; Li-Fi uses light-based communication.
B. Wi-Fi uses only fiber, while Li-Fi uses only copper.
C. Li-Fi is a routing protocol and Wi-Fi is a transport protocol.
D. Both are exclusively wired technologies.
Answer: A
Solution: Wi-Fi communicates using radio waves. Li-Fi uses modulated light, often from LED-based systems, and may require a suitable optical path or receiver arrangement.
Q187. Which wireless attack involves exploiting insecure Bluetooth implementations to access data without proper authorization?
A. Bluesnarfing
B. Route aggregation
C. VLAN tagging
D. TCP window scaling
Answer: A
Solution: Bluesnarfing refers to unauthorized access to information through vulnerable Bluetooth devices. Updated firmware, limited discoverability, and secure pairing practices reduce risk.
Q188. What is the main purpose of a Wireless Distribution System (WDS)?
A. Enable wireless bridging or interconnection between access points
B. Assign TCP sequence numbers
C. Encrypt every DNS query automatically
D. Replace IPv6 with IPv4
Answer: A
Solution: WDS can link access points wirelessly to extend network connectivity. Interoperability and security depend on the equipment and configuration.
Q189. What is the main purpose of a captive portal or walled garden in a network?
A. Restrict access to selected resources, often until a user completes an authentication or acceptance step
B. Guarantee that all web traffic is encrypted
C. Eliminate the need for a router
D. Prevent every form of malware
Answer: A
Solution: Captive portals commonly present login, payment, or acceptable-use pages on public Wi-Fi. A walled garden can permit access to selected destinations while restricting other traffic.
Q190. Which statement best describes a Content Delivery Network (CDN)?
A. A distributed system of servers that delivers content closer to users
B. A protocol for MAC address resolution
C. A single central computer that serves every internet user
D. A type of parity-check code
Answer: A
Solution: CDNs use geographically or topologically distributed points of presence to improve delivery performance and reduce load on origin servers.
Q191. Which network technology is commonly associated with dedicated high-speed storage connectivity between servers and storage systems?
A. SAN
B. PAN
C. BAN
D. MAN only
Answer: A
Solution: A Storage Area Network (SAN) provides block-level storage connectivity. Technologies include Fibre Channel and iSCSI over IP networks.
Q192. What is the main difference between NAS and SAN?
A. NAS commonly provides file-level access, while SAN commonly provides block-level storage access.
B. NAS always uses Bluetooth, while SAN always uses satellite links.
C. NAS cannot connect to a network.
D. SAN is exclusively a DNS protocol.
Answer: A
Solution: Network-Attached Storage typically exposes files through protocols such as NFS or SMB. SANs provide block storage that servers can use as disks.
Q193. Which technology is commonly used to connect NVMe storage devices over a network using an IP-based transport?
A. NVMe over Fabrics, including NVMe/TCP
B. POP3
C. ARP alone
D. CSMA/CD alone
Answer: A
Solution: NVMe over Fabrics extends NVMe access across supported transports. NVMe/TCP carries NVMe commands over TCP/IP.
Q194. A link has a bandwidth of 10 Mbps and a one-way propagation delay of 20 ms. How many bits can be in flight in one direction during that delay?
A. 20,000 bits
B. 100,000 bits
C. 200,000 bits
D. 500,000 bits
Answer: C
Solution:
This is the amount of data that can be transmitted during the one-way propagation delay, ignoring other overhead.
Q195. A 1,000-byte packet travels over a 2 Mbps link. Ignoring overhead, what is its transmission delay?
A. 0.4 ms
B. 2 ms
C. 4 ms
D. 8 ms
Answer: C
Solution: A 1,000-byte packet contains 8,000 bits.
Q196. A Stop-and-Wait protocol sends 1,000-bit frames over a 1 Mbps link. The one-way propagation delay is 10 ms, and ACK transmission time and processing time are negligible. What is the approximate utilization?
A. 2.5%
B. 4.76%
C. 50%
D. 100%
Answer: B
Solution: Frame transmission time is \(1000/10^6=1\) ms. The cycle time is approximately \(1+2(10)=21\) ms, so utilization is \(1/21\approx4.76\%\).
Q197. A sender uses a sliding window of 8 frames. Each frame contains 1,000 bits, and the link rate is 1 Mbps. Assuming continuous transmission is possible and ignoring ACK overhead, what is the maximum amount of payload data sent during one window?
A. 1,000 bits
B. 8,000 bits
C. 80,000 bits
D. 1,000,000 bits
Answer: B
Solution: The window contains \(8\times1000=8000\) bits. This is the data in one window, not necessarily the amount sent per second; throughput also depends on the round-trip time and acknowledgment behavior.
Q198. Which statement about the 802.11ac and 802.11ax Wi-Fi standards is correct?
A. 802.11ac is Wi-Fi 5, while 802.11ax is Wi-Fi 6/6E depending on the frequency bands supported.
B. 802.11ac is a wired Ethernet standard.
C. 802.11ax cannot support multiple users.
D. Both standards use only optical fiber.
Answer: A
Solution: Wi-Fi 5 corresponds to 802.11ac. Wi-Fi 6 and Wi-Fi 6E correspond to 802.11ax, with Wi-Fi 6E extending operation into the 6 GHz band where permitted.
Q199. Which statement about Network Time Security (NTS) and conventional NTP is correct?
A. NTS adds cryptographic security mechanisms for NTP time synchronization.
B. NTS is a substitute for IP addressing.
C. NTS is an Ethernet collision-detection algorithm.
D. NTS is used only to transfer files.
Answer: A
Solution: Network Time Security adds authentication and protection against certain attacks on NTP exchanges, using TLS for key establishment and authenticated NTP extension fields.
Q200. An organization wants to reduce unauthorized lateral movement, limit the impact of compromised accounts, and enforce least privilege across its network. Which approach is most appropriate?
A. Put every device on a single unrestricted VLAN.
B. Disable all authentication to simplify connectivity.
C. Combine network segmentation, role-based access controls, strong authentication, monitoring, and least-privilege policies.
D. Use WEP for all wireless networks.
Answer: C
Solution: A defense-in-depth approach combines segmentation, identity and access controls, monitoring, and secure configuration. No single control prevents every attack, but multiple complementary controls reduce risk and limit the impact of a compromise.
|
Topic |
Formula / Key fact |
|---|---|
|
Full-mesh links |
\(n(n-1)/2\) |
|
IPv4 usable hosts |
\(2^{32-p}-2\), for conventional subnets |
|
Bits per signal element |
\(\log_2 L\) |
|
Nyquist bit rate |
\(2B\log_2 L\) |
|
Shannon capacity |
\(B\log_2(1+S/N)\) |
|
Transmission delay |
Packet size in bits / link rate in bps |
|
Bandwidth-delay product |
Bandwidth × propagation delay |
|
Go-Back-N window |
Maximum \(2^k-1\) |
|
Selective Repeat window |
Maximum \(2^{k-1}\) |
|
TCP MSS (basic IPv4 example) |
MTU − IP header − TCP header |
Correction for Q43: The correct option is C — 15 kbps, not B. The calculation in its solution is correct: \(3000\log_2(1+31)=15{,}000\) bps