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Computer Networks

Computer Networks

Introduction

Understand how computers communicate through network protocols, devices and layered architectures.

Topic-Wise Overview

Network Models

Network types, topologies, protocol stacks and layered architecture

Physical and Data Link Layers

Transmission, switching, access methods and LAN technologies

Network Layer

IP addressing, IPv4, IPv6, subnetting, CIDR and routing

Transport Layer

Ports, sockets, connections, flow and congestion control

Applications and Wireless Networks

Application protocols, wireless networks and recent networking trends

Study Guidance

Explore the complete collection of 200 Computer Networks MCQs below, organized into four sets of 50 questions. Every question includes four options, the correct answer and an explanation. Topics include network models, Ethernet, Wi-Fi, IPv4/IPv6 addressing, routing, TCP/UDP, application protocols, security and modern network operations. Additional short questions and worked examples are planned.

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Browse Computer Science subjects

Computer Networks MCQs — Set 1 (Questions 1–50)

Choose an answer, then open its explanation.

Question 1. What is a computer network?

  1. Interconnected devices exchanging data
  2. A single isolated processor
  3. A type of operating system
  4. A programming language
Show correct answer and explanation

Correct answer: A. Interconnected devices exchanging data

Networks connect endpoints through communication links and protocols.

Question 2. What does LAN stand for?

  1. Large Access Node
  2. Local Area Network
  3. Long Address Number
  4. Linked Application Network
Show correct answer and explanation

Correct answer: B. Local Area Network

A LAN connects devices over a limited geographic area.

Question 3. What does WAN stand for?

  1. Wireless Access Number
  2. Web Application Node
  3. Wide Area Network
  4. Wired Area Namespace
Show correct answer and explanation

Correct answer: C. Wide Area Network

WANs interconnect networks across broad geographic distances.

Question 4. Which topology uses one central connection point?

  1. Ring topology
  2. Bus topology
  3. Full mesh topology
  4. Star topology
Show correct answer and explanation

Correct answer: D. Star topology

In a star, devices connect individually to a central device.

Question 5. Which topology connects every node directly to every other node?

  1. Full mesh
  2. Bus
  3. Ring
  4. Line
Show correct answer and explanation

Correct answer: A. Full mesh

A full mesh has a direct link between each pair of nodes.

Question 6. What is a networking protocol?

  1. A physical keyboard
  2. Agreed rules for communication
  3. Only a fiber-optic cable
  4. A disk filesystem
Show correct answer and explanation

Correct answer: B. Agreed rules for communication

Protocols specify data formats and exchange behavior.

Question 7. How many layers are in the OSI reference model?

  1. Four
  2. Five
  3. Seven
  4. Eight
Show correct answer and explanation

Correct answer: C. Seven

The OSI model describes seven conceptual layers.

Question 8. Which OSI layer is responsible for raw bit transmission?

  1. Network layer
  2. Application layer
  3. Transport layer
  4. Physical layer
Show correct answer and explanation

Correct answer: D. Physical layer

The physical layer deals with signaling bits over a medium.

Question 9. Which OSI layer handles frames and link-level addressing?

  1. Data link layer
  2. Session layer
  3. Application layer
  4. Transport layer
Show correct answer and explanation

Correct answer: A. Data link layer

Data link protocols frame data on a local link.

Question 10. Which OSI layer handles logical internetwork addressing and routing?

  1. Presentation layer
  2. Network layer
  3. Physical layer
  4. Session layer
Show correct answer and explanation

Correct answer: B. Network layer

The network layer supports forwarding across networks.

Question 11. Which layer provides end-to-end transport services?

  1. Physical layer
  2. Data link layer
  3. Transport layer
  4. Presentation layer
Show correct answer and explanation

Correct answer: C. Transport layer

Transport protocols support communication between endpoints.

Question 12. Which OSI layer provides services directly to applications?

  1. Data link layer
  2. Physical layer
  3. Network layer
  4. Application layer
Show correct answer and explanation

Correct answer: D. Application layer

Application-layer protocols support network applications.

Question 13. Which transport protocols are part of the Internet suite?

  1. TCP and UDP
  2. HTTP and HTML
  3. IP and Ethernet
  4. ARP and DNS only
Show correct answer and explanation

Correct answer: A. TCP and UDP

TCP and UDP are transport protocols used over IP.

Question 14. What is encapsulation?

  1. Removing every packet header
  2. Adding protocol headers as data moves down layers
  3. Physically twisting wires
  4. Converting a LAN to a WAN
Show correct answer and explanation

Correct answer: B. Adding protocol headers as data moves down layers

Each lower layer wraps higher-layer data in its own protocol format.

Question 15. What is decapsulation?

  1. Adding a second physical cable
  2. Encrypting a hard drive
  3. Processing and removing relevant protocol headers at a receiver
  4. Repeating every frame
Show correct answer and explanation

Correct answer: C. Processing and removing relevant protocol headers at a receiver

Receiving protocol layers interpret headers to deliver the payload upward.

Question 16. What is bandwidth commonly measured in?

  1. Seconds per packet only
  2. Meters per second
  3. Bytes per address
  4. Bits per second
Show correct answer and explanation

Correct answer: D. Bits per second

Link transmission rates are commonly expressed in bps.

Question 17. What is propagation delay?

  1. Time for a signal to travel across a medium
  2. Time to create a file
  3. Number of bits in a packet
  4. Time spent compiling a program
Show correct answer and explanation

Correct answer: A. Time for a signal to travel across a medium

Propagation delay depends on distance and signal speed.

Question 18. What is transmission delay?

  1. Distance divided by light speed only
  2. Packet length divided by link transmission rate
  3. CPU clock period
  4. Router uptime
Show correct answer and explanation

Correct answer: B. Packet length divided by link transmission rate

Sending L bits on a link of rate R takes L/R seconds.

Question 19. A 1000-bit packet on a 1000-bit/s link takes how long to transmit?

  1. 0.1 second
  2. 10 seconds
  3. 1 second
  4. 1000 seconds
Show correct answer and explanation

Correct answer: C. 1 second

Transmission delay is 1000/1000 = 1 second.

Question 20. What causes queuing delay?

  1. Signal speed alone
  2. The MAC address format
  3. File permissions
  4. Waiting for service at a network device
Show correct answer and explanation

Correct answer: D. Waiting for service at a network device

Packets wait when the outgoing link or processing resources are busy.

Question 21. What is packet loss?

  1. Failure of a packet to reach its destination
  2. Sending a packet successfully
  3. Encoding a packet as bits
  4. Increasing an MTU
Show correct answer and explanation

Correct answer: A. Failure of a packet to reach its destination

Packets may be dropped by congestion or transmission errors.

Question 22. What does throughput measure?

  1. Length of a network cable
  2. Successfully delivered data per unit time
  3. Number of software processes
  4. Count of router interfaces only
Show correct answer and explanation

Correct answer: B. Successfully delivered data per unit time

Throughput measures effective delivery rate.

Question 23. What is latency?

  1. The number of network hosts
  2. A switch port number
  3. Elapsed time for data to travel or a request to be served
  4. Only maximum bandwidth
Show correct answer and explanation

Correct answer: C. Elapsed time for data to travel or a request to be served

Latency measures communication delay.

Question 24. What is jitter?

  1. Permanent link capacity
  2. The number of IP addresses
  3. Only packet size
  4. Variation in packet delay
Show correct answer and explanation

Correct answer: D. Variation in packet delay

Jitter is variation in delay across packets.

Question 25. What is a hub in classic Ethernet networking?

  1. A physical-layer repeater sending signals to other ports
  2. A device forwarding based on IP routes
  3. A DNS database
  4. A TCP congestion algorithm
Show correct answer and explanation

Correct answer: A. A physical-layer repeater sending signals to other ports

A traditional hub repeats incoming signals rather than learning MAC addresses.

Question 26. What does a network switch normally use to forward Ethernet frames?

  1. TCP port numbers only
  2. MAC addresses
  3. Web URLs
  4. Application usernames
Show correct answer and explanation

Correct answer: B. MAC addresses

A Layer 2 switch learns address-to-port associations.

Question 27. What is a router’s primary role?

  1. Translate source code
  2. Store web pages only
  3. Forward packets between IP networks
  4. Generate wireless encryption keys
Show correct answer and explanation

Correct answer: C. Forward packets between IP networks

Routers use IP routing and forwarding information.

Question 28. What does a repeater do?

  1. Assign IP addresses
  2. Resolve domain names
  3. Filter SQL queries
  4. Regenerate or relay signals to extend communication
Show correct answer and explanation

Correct answer: D. Regenerate or relay signals to extend communication

Repeaters operate on signals at the physical layer.

Question 29. What is a MAC address?

  1. A link-layer interface identifier
  2. A website domain
  3. A transport port
  4. A DNS record
Show correct answer and explanation

Correct answer: A. A link-layer interface identifier

Ethernet MAC addresses identify interfaces on a local link.

Question 30. What is the conventional length of an Ethernet MAC address?

  1. 16 bits
  2. 48 bits
  3. 32 bits
  4. 128 bits
Show correct answer and explanation

Correct answer: B. 48 bits

Common Ethernet MAC addresses consist of 48 bits.

Question 31. What is an Ethernet frame?

  1. A TCP connection
  2. An IP routing protocol
  3. A data-link unit carrying payload and control fields
  4. A wireless frequency band
Show correct answer and explanation

Correct answer: C. A data-link unit carrying payload and control fields

Ethernet frames carry link-layer source and destination addresses.

Question 32. Which address does a switch learn from an incoming Ethernet frame?

  1. Destination IP only
  2. Source TCP port only
  3. Website hostname
  4. Source MAC address
Show correct answer and explanation

Correct answer: D. Source MAC address

Learning switches associate a source MAC with the ingress port.

Question 33. What is Ethernet’s broadcast destination MAC?

  1. FF:FF:FF:FF:FF:FF
  2. 00:00:00:00:00:00
  3. 127.0.0.1
  4. 255.255.255.255
Show correct answer and explanation

Correct answer: A. FF:FF:FF:FF:FF:FF

All-ones Ethernet destination MAC represents broadcast.

Question 34. What is CSMA/CD associated with?

  1. Modern full-duplex switched Ethernet collision-free operation
  2. Legacy shared half-duplex Ethernet
  3. IPv6 routing headers
  4. DNS zone transfers
Show correct answer and explanation

Correct answer: B. Legacy shared half-duplex Ethernet

CSMA/CD managed collisions on shared half-duplex Ethernet.

Question 35. Why is CSMA/CD generally unnecessary on full-duplex switched Ethernet?

  1. Packets cannot be transmitted
  2. MAC addresses are absent
  3. Separate full-duplex links have no shared collision domain
  4. Routers disable Ethernet frames
Show correct answer and explanation

Correct answer: C. Separate full-duplex links have no shared collision domain

Full-duplex point-to-point switched links do not use collision detection.

Question 36. What is a VLAN?

  1. A type of fiber connector
  2. An IP address length
  3. A web server file
  4. A logical separation of Layer 2 networks
Show correct answer and explanation

Correct answer: D. A logical separation of Layer 2 networks

VLANs divide switching infrastructure into separate broadcast domains.

Question 37. What is the common Ethernet VLAN tagging standard?

  1. IEEE 802.1Q
  2. IEEE 802.11ax
  3. TCP RFC 793
  4. DNS RFC 1035
Show correct answer and explanation

Correct answer: A. IEEE 802.1Q

802.1Q specifies VLAN tagging in Ethernet frames.

Question 38. A VLAN trunk link typically carries

  1. Only one TCP flow
  2. Traffic for multiple VLANs
  3. No frames
  4. Only routing updates
Show correct answer and explanation

Correct answer: B. Traffic for multiple VLANs

Trunks transport tagged VLAN traffic across links.

Question 39. What is a broadcast domain?

  1. Every system connected to the Internet
  2. Only one CPU core
  3. A set of devices reached by a Layer 2 broadcast
  4. A group of DNS servers exclusively
Show correct answer and explanation

Correct answer: C. A set of devices reached by a Layer 2 broadcast

Layer 2 broadcasts normally remain within a broadcast domain.

Question 40. A router normally separates

  1. Every TCP port number
  2. All applications on a host
  3. Every MAC address from its interface
  4. Broadcast domains
Show correct answer and explanation

Correct answer: D. Broadcast domains

Routers usually do not forward ordinary link-layer broadcasts.

Question 41. Why use the Spanning Tree Protocol?

  1. To prevent forwarding loops in switched Layer 2 networks
  2. To compute shortest IP routes across the Internet
  3. To allocate TCP ports
  4. To encrypt DNS names
Show correct answer and explanation

Correct answer: A. To prevent forwarding loops in switched Layer 2 networks

STP establishes a loop-free active switching topology.

Question 42. What is an access point?

  1. A DNS root server
  2. A device providing Wi-Fi access to a network
  3. A CPU cache
  4. A SQL transaction manager
Show correct answer and explanation

Correct answer: B. A device providing Wi-Fi access to a network

An AP connects wireless stations to network infrastructure.

Question 43. Which IEEE family specifies Wi-Fi?

  1. 802.3 only
  2. 802.1Q only
  3. 802.11
  4. 802.15.4 only
Show correct answer and explanation

Correct answer: C. 802.11

IEEE 802.11 defines wireless LAN technologies.

Question 44. Which IEEE standard family specifies conventional Ethernet?

  1. 802.11
  2. 802.15.1
  3. 802.16 only
  4. 802.3
Show correct answer and explanation

Correct answer: D. 802.3

IEEE 802.3 defines Ethernet standards.

Question 45. What is SSID in Wi-Fi?

  1. A wireless network identifier
  2. A TCP acknowledgement
  3. An IPv6 prefix length
  4. An Ethernet checksum
Show correct answer and explanation

Correct answer: A. A wireless network identifier

The SSID names a wireless network.

Question 46. What is the main purpose of WPA2 or WPA3?

  1. Assign IPv6 routes
  2. Protect Wi-Fi access and traffic using security mechanisms
  3. Replace TCP entirely
  4. Increase fiber signal speed
Show correct answer and explanation

Correct answer: B. Protect Wi-Fi access and traffic using security mechanisms

WPA standards provide authentication and encryption mechanisms for Wi-Fi.

Question 47. Which access method is traditionally associated with Wi-Fi?

  1. CSMA/CD for all links
  2. Token ring only
  3. CSMA/CA
  4. ALOHA without carrier sensing only
Show correct answer and explanation

Correct answer: C. CSMA/CA

Wi-Fi uses collision-avoidance mechanisms rather than conventional Ethernet collision detection.

Question 48. What is attenuation in communication media?

  1. A higher packet rate
  2. Assignment of a subnet
  3. A routing loop
  4. Reduction in signal strength over distance or medium
Show correct answer and explanation

Correct answer: D. Reduction in signal strength over distance or medium

Signal power decreases as it propagates through a medium.

Question 49. What is electromagnetic interference?

  1. Unwanted electromagnetic energy disturbing signals
  2. A database index
  3. A TCP flag
  4. An IP subnet mask
Show correct answer and explanation

Correct answer: A. Unwanted electromagnetic energy disturbing signals

Interference may degrade data transmission quality.

Question 50. What advantage does optical fiber commonly have?

  1. No installation cost
  2. High bandwidth with resistance to electromagnetic interference
  3. Unlimited signal speed
  4. No need for transceivers
Show correct answer and explanation

Correct answer: B. High bandwidth with resistance to electromagnetic interference

Optical fiber carries light signals and is not affected like copper by EMI.

Computer Networks MCQs — Set 2 (Questions 51–100)

Choose the answer, then open the explanation.

Question 51. IPv4 address length?

  1. 16 bits
  2. 48 bits
  3. 32 bits
  4. 128 bits
Show correct answer and explanation

Correct answer: C. 32 bits

IPv4 addresses contain 32 bits.

Question 52. IPv6 address length?

  1. 32 bits
  2. 48 bits
  3. 64 bits
  4. 128 bits
Show correct answer and explanation

Correct answer: D. 128 bits

IPv6 addresses contain 128 bits.

Question 53. IPv4 loopback example?

  1. 127.0.0.1
  2. 192.0.2.1
  3. 224.0.0.1
  4. 255.255.255.255
Show correct answer and explanation

Correct answer: A. 127.0.0.1

127.0.0.1 is in the IPv4 loopback block.

Question 54. Private IPv4 block?

  1. 8.8.8.0/24
  2. 192.168.0.0/16
  3. 224.0.0.0/4
  4. 198.51.100.0/24
Show correct answer and explanation

Correct answer: B. 192.168.0.0/16

192.168.0.0/16 is an RFC 1918 private range.

Question 55. Another private IPv4 block?

  1. 11.0.0.0/8
  2. 127.0.0.0/8
  3. 10.0.0.0/8
  4. 169.254.0.0/16
Show correct answer and explanation

Correct answer: C. 10.0.0.0/8

10.0.0.0/8 is private IPv4 address space.

Question 56. IPv4 link-local range?

  1. 172.32.0.0/16
  2. 192.0.2.0/24
  3. 224.0.0.0/4
  4. 169.254.0.0/16
Show correct answer and explanation

Correct answer: D. 169.254.0.0/16

IPv4 link-local addresses occupy 169.254.0.0/16.

Question 57. IPv4 subnet mask purpose?

  1. Mark network prefix bits
  2. Specify TCP port
  3. Identify cable material
  4. Identify DNS authority
Show correct answer and explanation

Correct answer: A. Mark network prefix bits

The mask distinguishes network and host address bits.

Question 58. Host bits in a /24 IPv4 prefix?

  1. 24
  2. 8
  3. 16
  4. 32
Show correct answer and explanation

Correct answer: B. 8

32 minus 24 leaves eight host bits.

Question 59. Total IPv4 addresses in /26?

  1. 26
  2. 32
  3. 64
  4. 128
Show correct answer and explanation

Correct answer: C. 64

Six host bits yield 2 to the power 6, or 64 addresses.

Question 60. Conventional usable IPv4 hosts in /26?

  1. 64
  2. 60
  3. 126
  4. 62
Show correct answer and explanation

Correct answer: D. 62

The network and directed broadcast addresses are normally excluded.

Question 61. Network address of 192.168.1.70/26?

  1. 192.168.1.64
  2. 192.168.1.0
  3. 192.168.1.70
  4. 192.168.1.128
Show correct answer and explanation

Correct answer: A. 192.168.1.64

A /26 block starting at .64 includes .70.

Question 62. Broadcast address of 192.168.1.70/26?

  1. 192.168.1.63
  2. 192.168.1.127
  3. 192.168.1.255
  4. 192.168.1.71
Show correct answer and explanation

Correct answer: B. 192.168.1.127

The block runs from .64 to .127.

Question 63. CIDR full form?

  1. Classical Internet Data Relay
  2. Central Internet Device Routing
  3. Classless Inter-Domain Routing
  4. Connected Interface Data Rate
Show correct answer and explanation

Correct answer: C. Classless Inter-Domain Routing

CIDR supports variable-length prefix routing.

Question 64. IPv4 field limiting packet lifetime?

  1. Source MAC
  2. TCP window
  3. DNS TTL
  4. Time to Live
Show correct answer and explanation

Correct answer: D. Time to Live

Routers decrement TTL on forwarding.

Question 65. IPv6 equivalent of IPv4 TTL?

  1. Hop Limit
  2. Flow Label
  3. Payload Length
  4. Traffic Class
Show correct answer and explanation

Correct answer: A. Hop Limit

IPv6 uses the Hop Limit field.

Question 66. Protocol for IP diagnostics?

  1. SMTP
  2. ICMP
  3. FTP
  4. POP3
Show correct answer and explanation

Correct answer: B. ICMP

ICMP communicates network errors and diagnostic messages.

Question 67. Common tool using ICMP echo?

  1. ssh
  2. scp
  3. ping
  4. ftp
Show correct answer and explanation

Correct answer: C. ping

Ping commonly probes reachability with ICMP echoes.

Question 68. Traceroute helps reveal?

  1. Disk sectors
  2. CPU schedule
  3. Database joins
  4. Forwarding hops toward a destination
Show correct answer and explanation

Correct answer: D. Forwarding hops toward a destination

Traceroute uses expiring hop limits and responses.

Question 69. ARP resolves on local IPv4 link?

  1. IPv4 address to MAC address
  2. Domain to IPv4 address
  3. TCP port to process
  4. File to inode
Show correct answer and explanation

Correct answer: A. IPv4 address to MAC address

ARP finds a neighbor’s link-layer address.

Question 70. IPv6 address resolution mechanism?

  1. HTTP
  2. Neighbor Discovery Protocol
  3. FTP
  4. SMTP
Show correct answer and explanation

Correct answer: B. Neighbor Discovery Protocol

IPv6 Neighbor Discovery uses ICMPv6.

Question 71. DHCP purpose?

  1. File encryption
  2. CPU measurements
  3. Automatic IP configuration
  4. Page rendering
Show correct answer and explanation

Correct answer: C. Automatic IP configuration

DHCP supplies client network configuration.

Question 72. Default gateway meaning?

  1. Local file server
  2. Local MAC address
  3. DNS suffix
  4. Router for nonlocal destinations
Show correct answer and explanation

Correct answer: D. Router for nonlocal destinations

The gateway handles traffic for destinations outside the directly connected networks.

Question 73. NAT commonly rewrites?

  1. IP addresses and sometimes ports
  2. Fonts
  3. Cable length
  4. Root DNS names
Show correct answer and explanation

Correct answer: A. IP addresses and sometimes ports

NAT changes IP header addresses and sometimes transport ports.

Question 74. PAT allows?

  1. One public address per process
  2. Sharing a public address using port mappings
  3. No transport ports
  4. Replacing IP with Ethernet
Show correct answer and explanation

Correct answer: B. Sharing a public address using port mappings

Port translation distinguishes multiple connections.

Question 75. Unspecified IPv4 address?

  1. 127.0.0.1
  2. 8.8.8.8
  3. 0.0.0.0
  4. 255.255.255.255
Show correct answer and explanation

Correct answer: C. 0.0.0.0

0.0.0.0 denotes an unspecified IPv4 address.

Question 76. IPv6 loopback address?

  1. ::
  2. ff02::1
  3. fe80::1
  4. ::1
Show correct answer and explanation

Correct answer: D. ::1

::1 is the IPv6 loopback address.

Question 77. IPv6 unspecified address?

  1. ::
  2. ::1
  3. ff02::1
  4. fe80::1
Show correct answer and explanation

Correct answer: A. ::

The all-zero address is unspecified.

Question 78. IPv6 link-local prefix?

  1. ff00::/8
  2. fe80::/10
  3. 2000::/3
  4. ::1/128
Show correct answer and explanation

Correct answer: B. fe80::/10

Link-local unicast occupies fe80::/10.

Question 79. IPv6 multicast prefix?

  1. fe80::/10
  2. ::1/128
  3. ff00::/8
  4. fc00::/7
Show correct answer and explanation

Correct answer: C. ff00::/8

Multicast IPv6 addresses start with ff.

Question 80. IPv6 unique local prefix?

  1. ff00::/8
  2. fe80::/10
  3. ::/0
  4. fc00::/7
Show correct answer and explanation

Correct answer: D. fc00::/7

Unique local IPv6 space uses fc00::/7.

Question 81. Router’s basic network-layer function?

  1. Forward packets between networks
  2. Choose fonts
  3. Allocate registers
  4. Compile websites
Show correct answer and explanation

Correct answer: A. Forward packets between networks

Routers select next hops using forwarding tables.

Question 82. Routing table content?

  1. DNS passwords
  2. Destination prefixes and next-hop information
  3. Only cable diagrams
  4. Only row locks
Show correct answer and explanation

Correct answer: B. Destination prefixes and next-hop information

Routing tables identify where packets should go.

Question 83. Longest-prefix route matching?

  1. Oldest route
  2. Shortest text label
  3. Most specific matching prefix
  4. Highest numerical next hop
Show correct answer and explanation

Correct answer: C. Most specific matching prefix

IP forwarding prefers the matching route with greatest prefix length.

Question 84. IPv4 default route?

  1. 127.0.0.0/8
  2. 224.0.0.0/4
  3. 255.255.255.255/32
  4. 0.0.0.0/0
Show correct answer and explanation

Correct answer: D. 0.0.0.0/0

A /0 route matches all IPv4 destinations.

Question 85. Distance-vector routing protocol?

  1. RIP
  2. OSPF
  3. IS-IS
  4. HTTP
Show correct answer and explanation

Correct answer: A. RIP

RIP uses distance-vector updates and hop count.

Question 86. Link-state interior routing protocol?

  1. RIP
  2. OSPF
  3. DNS
  4. FTP
Show correct answer and explanation

Correct answer: B. OSPF

OSPF exchanges link-state information.

Question 87. Algorithm central to OSPF path calculation?

  1. Bubble sort
  2. K-means
  3. Dijkstra’s shortest-path algorithm
  4. Minimax
Show correct answer and explanation

Correct answer: C. Dijkstra’s shortest-path algorithm

OSPF computes shortest-path trees using link-state data.

Question 88. Internet interdomain routing protocol?

  1. ARP
  2. DHCP
  3. ICMP Echo
  4. BGP
Show correct answer and explanation

Correct answer: D. BGP

BGP exchanges reachability across autonomous systems.

Question 89. Internet autonomous system?

  1. Networks under a common routing policy
  2. One Ethernet cable
  3. An isolated CPU
  4. Password database
Show correct answer and explanation

Correct answer: A. Networks under a common routing policy

An AS represents networks administered under common routing policy.

Question 90. Route aggregation meaning?

  1. Split packets into frames
  2. Summarize multiple prefixes into a larger prefix
  3. Combine UDP and TCP
  4. Add masks arithmetically
Show correct answer and explanation

Correct answer: B. Summarize multiple prefixes into a larger prefix

Summarization reduces routing advertisements where possible.

Question 91. IPv4 fragmentation?

  1. Encrypt twice
  2. Duplicate every packet
  3. Split a datagram into smaller fragments when allowed
  4. Join Ethernet frames
Show correct answer and explanation

Correct answer: C. Split a datagram into smaller fragments when allowed

IPv4 packets may be fragmented to fit path MTU.

Question 92. MTU full form?

  1. Minimum Transport Utility
  2. Multiple Tunnel User
  3. Main Transfer URL
  4. Maximum Transmission Unit
Show correct answer and explanation

Correct answer: D. Maximum Transmission Unit

MTU limits packet payload size on a link interface.

Question 93. Path MTU Discovery goal?

  1. Find a suitable packet size for the path
  2. Find shortest DNS name
  3. Select CPU scheduler
  4. Discover MAC vendor
Show correct answer and explanation

Correct answer: A. Find a suitable packet size for the path

PMTUD helps avoid fragmentation or packet-too-big failures.

Question 94. Which IP version prohibits router fragmentation?

  1. IPv4
  2. IPv6
  3. Both require router fragmentation
  4. Neither permits endpoint fragmentation
Show correct answer and explanation

Correct answer: B. IPv6

IPv6 routers do not fragment forwarded packets.

Question 95. DNS record for IPv4 address?

  1. AAAA
  2. MX
  3. A
  4. PTR
Show correct answer and explanation

Correct answer: C. A

A records hold IPv4 addresses.

Question 96. DNS record for IPv6 address?

  1. A
  2. MX
  3. TXT
  4. AAAA
Show correct answer and explanation

Correct answer: D. AAAA

AAAA records hold IPv6 addresses.

Question 97. DNS record for mail exchanger?

  1. MX
  2. PTR
  3. AAAA
  4. CNAME
Show correct answer and explanation

Correct answer: A. MX

MX records list mail servers.

Question 98. DNS alias record?

  1. A
  2. CNAME
  3. MX
  4. NS
Show correct answer and explanation

Correct answer: B. CNAME

CNAME aliases one domain name to another.

Question 99. DNS caching benefit?

  1. Disable all lookups
  2. Encrypt IP headers
  3. Reuse answers during their permitted cache lifetime
  4. Assign MAC addresses
Show correct answer and explanation

Correct answer: C. Reuse answers during their permitted cache lifetime

Cached responses reduce repeated DNS queries.

Question 100. DNS TTL meaning?

  1. Router lifespan
  2. Cable speed
  3. DNS packet count
  4. Permitted caching lifetime for a resource record
Show correct answer and explanation

Correct answer: D. Permitted caching lifetime for a resource record

Time to Live indicates how long responses can normally be cached.

Computer Networks MCQs — Set 3 (Questions 101–150)

Choose an answer and reveal the explanation.

Question 101. Which protocol provides a connection-oriented reliable byte stream?

  1. TCP
  2. UDP
  3. IP
  4. ICMP
Show correct answer and explanation

Correct answer: A. TCP

TCP provides ordered reliable byte-stream transport between endpoints.

Question 102. Which transport protocol sends independent datagrams without built-in delivery guarantees?

  1. TCP
  2. UDP
  3. TLS
  4. HTTP
Show correct answer and explanation

Correct answer: B. UDP

UDP is connectionless and does not itself guarantee delivery or order.

Question 103. How large is a standard TCP port number?

  1. 8 bits
  2. 32 bits
  3. 16 bits
  4. 64 bits
Show correct answer and explanation

Correct answer: C. 16 bits

TCP port fields are 16 bits long.

Question 104. What is the highest possible TCP port number?

  1. 65536
  2. 32767
  3. 1024
  4. 65535
Show correct answer and explanation

Correct answer: D. 65535

A 16-bit unsigned port ranges from 0 through 65535.

Question 105. What identifies a TCP connection uniquely within the relevant network context?

  1. Source and destination IP addresses and TCP ports
  2. Only the destination port
  3. Only the source IP
  4. Only the Ethernet MAC
Show correct answer and explanation

Correct answer: A. Source and destination IP addresses and TCP ports

A TCP connection is distinguished by its four endpoint address and port values.

Question 106. What is the usual first segment of TCP’s three-way handshake?

  1. ACK without SYN
  2. SYN
  3. FIN
  4. RST
Show correct answer and explanation

Correct answer: B. SYN

The active opener normally sends a SYN segment.

Question 107. Which flag combination typically appears in the second step of TCP connection establishment?

  1. FIN and RST
  2. PSH only
  3. SYN and ACK
  4. URG only
Show correct answer and explanation

Correct answer: C. SYN and ACK

The responder acknowledges the first SYN and sends its own SYN.

Question 108. What does TCP’s ACK number normally signify?

  1. The last physical frame sent
  2. The IP address of the peer
  3. The number of routers traversed
  4. The next byte sequence number expected
Show correct answer and explanation

Correct answer: D. The next byte sequence number expected

Cumulative acknowledgments name the next expected byte.

Question 109. What is the purpose of TCP sequence numbers?

  1. Order bytes and detect missing data
  2. Assign DNS names
  3. Choose Wi-Fi channels
  4. Identify Ethernet manufacturers
Show correct answer and explanation

Correct answer: A. Order bytes and detect missing data

Sequence numbers label positions in the TCP byte stream.

Question 110. Which TCP flag requests orderly termination of one data direction?

  1. SYN
  2. FIN
  3. ECE
  4. PSH
Show correct answer and explanation

Correct answer: B. FIN

FIN marks the end of a sender’s byte stream.

Question 111. What does an RST segment generally indicate?

  1. Request DNS resolution
  2. Negotiate Ethernet speed
  3. Abruptly reset or refuse a TCP connection
  4. Renew a DHCP lease
Show correct answer and explanation

Correct answer: C. Abruptly reset or refuse a TCP connection

TCP RST terminates or rejects a connection state.

Question 112. What is a TCP retransmission for?

  1. Increasing an IPv6 prefix
  2. Creating an ARP entry
  3. Changing the MAC address
  4. Resending data believed to be lost
Show correct answer and explanation

Correct answer: D. Resending data believed to be lost

Retransmissions recover from segments that were lost or not acknowledged.

Question 113. What is a retransmission timeout (RTO)?

  1. Time threshold after which unacknowledged data may be resent
  2. Router boot duration
  3. DNS record lifetime only
  4. Time to transmit one bit
Show correct answer and explanation

Correct answer: A. Time threshold after which unacknowledged data may be resent

TCP estimates an RTO using network round-trip behavior.

Question 114. TCP flow control protects primarily

  1. Routers from all congestion
  2. The receiving endpoint from being overwhelmed
  3. The DNS server from queries
  4. Wi-Fi signals from interference
Show correct answer and explanation

Correct answer: B. The receiving endpoint from being overwhelmed

The advertised receive window limits outstanding data according to receiver capacity.

Question 115. TCP congestion control primarily responds to

  1. Only application file permissions
  2. Domain registration
  3. Network path congestion
  4. The number of CPU cores
Show correct answer and explanation

Correct answer: C. Network path congestion

Congestion algorithms regulate sending to limit overload in the path.

Question 116. What is TCP’s congestion window commonly abbreviated as?

  1. rwin
  2. mtu
  3. ssid
  4. cwnd
Show correct answer and explanation

Correct answer: D. cwnd

cwnd limits flight size based on congestion control.

Question 117. What does TCP’s advertised receive window commonly represent?

  1. Available receiver buffer capacity
  2. The router’s forwarding table size
  3. Total DNS entries
  4. The Wi-Fi channel width
Show correct answer and explanation

Correct answer: A. Available receiver buffer capacity

The receiver communicates available buffering to the sender.

Question 118. Which quantity commonly bounds TCP’s outstanding unacknowledged data?

  1. Only IPv4 address length
  2. The minimum of congestion and receive windows
  3. The DNS TTL
  4. The MAC address length
Show correct answer and explanation

Correct answer: B. The minimum of congestion and receive windows

Both path congestion control and receiver flow control constrain flight size.

Question 119. What is TCP slow start?

  1. A permanently fixed one-byte transfer rate
  2. A DNS lookup mechanism
  3. An algorithm phase in which the congestion window grows rapidly with acknowledgments
  4. A Wi-Fi authentication step
Show correct answer and explanation

Correct answer: C. An algorithm phase in which the congestion window grows rapidly with acknowledgments

Slow start increases cwnd rapidly until a threshold or congestion signal.

Question 120. What is a duplicate acknowledgment in TCP?

  1. A second DNS A record
  2. A copy of an Ethernet switch
  3. A duplicate router interface
  4. An ACK repeating a previously acknowledged next-byte value
Show correct answer and explanation

Correct answer: D. An ACK repeating a previously acknowledged next-byte value

Duplicate ACKs can suggest out-of-order arrival or missing segments.

Question 121. What is the bandwidth-delay product?

  1. Link or path rate multiplied by round-trip time
  2. Packet size divided by bit error rate
  3. IPv4 address multiplied by subnet mask
  4. The number of router hops squared
Show correct answer and explanation

Correct answer: A. Link or path rate multiplied by round-trip time

BDP estimates the amount of data needed in flight to utilize a path.

Question 122. A 10 Mb/s path with RTT 0.1 s has a bandwidth-delay product of approximately

  1. 10 megabits
  2. 1 megabit
  3. 100 megabits
  4. 0.01 megabit
Show correct answer and explanation

Correct answer: B. 1 megabit

10 megabits per second times 0.1 seconds equals 1 megabit.

Question 123. Which transport mechanism distinguishes application endpoints on the same host?

  1. Only subnet masks
  2. Only physical layer symbols
  3. Port numbers
  4. Routing metrics
Show correct answer and explanation

Correct answer: C. Port numbers

Transport ports support multiplexing and demultiplexing.

Question 124. What is a socket in TCP/IP programming?

  1. A dedicated RAM chip
  2. A DNS root zone
  3. A router configuration file
  4. A communication endpoint associated with protocol and addressing state
Show correct answer and explanation

Correct answer: D. A communication endpoint associated with protocol and addressing state

Sockets expose transport communication to processes.

Question 125. Which common service uses TCP port 80 by convention?

  1. HTTP
  2. DNS over UDP
  3. SSH
  4. SMTP submission
Show correct answer and explanation

Correct answer: A. HTTP

HTTP traditionally uses TCP port 80.

Question 126. Which service commonly uses TCP port 443?

  1. Telnet
  2. HTTPS
  3. FTP control
  4. POP3
Show correct answer and explanation

Correct answer: B. HTTPS

HTTPS normally runs over TLS with TCP port 443, although HTTP/3 uses UDP.

Question 127. Which service commonly uses TCP port 22?

  1. HTTP
  2. SMTP
  3. SSH
  4. NTP
Show correct answer and explanation

Correct answer: C. SSH

Secure Shell conventionally uses TCP port 22.

Question 128. Which application protocol typically uses UDP port 53 for ordinary queries?

  1. SSH
  2. FTP
  3. IMAP
  4. DNS
Show correct answer and explanation

Correct answer: D. DNS

Most conventional DNS queries use UDP 53, with TCP also supported.

Question 129. Which service commonly uses UDP port 67 on the server side?

  1. DHCPv4
  2. HTTPS
  3. SSH
  4. IMAPS
Show correct answer and explanation

Correct answer: A. DHCPv4

DHCPv4 servers listen on UDP port 67.

Question 130. Which protocol is associated with UDP port 123?

  1. HTTP
  2. NTP
  3. SMTP
  4. SFTP
Show correct answer and explanation

Correct answer: B. NTP

Network Time Protocol uses UDP port 123.

Question 131. What does HTTP stand for?

  1. Host Transport Tunnel Protocol
  2. High Throughput Text Process
  3. Hypertext Transfer Protocol
  4. Hybrid Telemetry Transfer Port
Show correct answer and explanation

Correct answer: C. Hypertext Transfer Protocol

HTTP defines methods and semantics for web requests and responses.

Question 132. Which HTTP method conventionally retrieves a representation without requesting a state change?

  1. POST
  2. DELETE
  3. PATCH
  4. GET
Show correct answer and explanation

Correct answer: D. GET

GET has safe semantics for retrieving resources.

Question 133. Which HTTP method is generally used to create or submit processing data?

  1. POST
  2. HEAD
  3. TRACE
  4. OPTIONS
Show correct answer and explanation

Correct answer: A. POST

POST submits data for processing according to resource semantics.

Question 134. Which HTTP status code means successful ordinary retrieval?

  1. 301
  2. 200
  3. 404
  4. 503
Show correct answer and explanation

Correct answer: B. 200

HTTP 200 indicates a successful request.

Question 135. Which HTTP status code commonly means resource not found?

  1. 201
  2. 302
  3. 404
  4. 500
Show correct answer and explanation

Correct answer: C. 404

A 404 response indicates that the target resource was not found.

Question 136. Which HTTP status code signifies permanent redirection?

  1. 200
  2. 400
  3. 503
  4. 301
Show correct answer and explanation

Correct answer: D. 301

301 Moved Permanently indicates a permanent new resource location.

Question 137. Which HTTP status code typically means internal server error?

  1. 500
  2. 204
  3. 304
  4. 401
Show correct answer and explanation

Correct answer: A. 500

A 500 response indicates an unexpected server-side failure.

Question 138. What is HTTP statelessness?

  1. TCP connections can never be reused
  2. Each request is interpreted without requiring built-in application session state from previous requests
  3. Web servers cannot store files
  4. Cookies cannot exist
Show correct answer and explanation

Correct answer: B. Each request is interpreted without requiring built-in application session state from previous requests

Applications can layer sessions over a stateless request-response protocol.

Question 139. What are HTTP cookies commonly used for?

  1. Routing IP packets
  2. Assigning MAC addresses
  3. Maintaining client-related state such as session identifiers
  4. Encrypting Ethernet frames by themselves
Show correct answer and explanation

Correct answer: C. Maintaining client-related state such as session identifiers

Cookies let clients return stored state in later HTTP requests.

Question 140. What does TLS mainly provide to applications?

  1. Physical cable testing
  2. IPv4 subnet assignment
  3. Disk block allocation
  4. Authenticated and encrypted communication channels
Show correct answer and explanation

Correct answer: D. Authenticated and encrypted communication channels

TLS protects application data against interception and tampering.

Question 141. What does the SNI extension in a TLS handshake commonly convey?

  1. The server hostname the client wants to reach
  2. The client MAC address
  3. The router hop count
  4. The DHCP lease time
Show correct answer and explanation

Correct answer: A. The server hostname the client wants to reach

Server Name Indication helps hosts select certificates for the requested domain.

Question 142. What does a digital certificate help bind?

  1. A MAC address to a CPU core
  2. A public key to an authenticated identity or domain
  3. A file size to an inode
  4. A TCP port to a password
Show correct answer and explanation

Correct answer: B. A public key to an authenticated identity or domain

Certificates support peer authentication via trusted issuers and validation.

Question 143. Which protocol is commonly used for transferring email between mail servers?

  1. IMAP
  2. HTTP
  3. SMTP
  4. ARP
Show correct answer and explanation

Correct answer: C. SMTP

Simple Mail Transfer Protocol carries outgoing and relayed email.

Question 144. Which protocol commonly lets clients access and manage mail on a server?

  1. ARP
  2. RIP
  3. ICMP
  4. IMAP
Show correct answer and explanation

Correct answer: D. IMAP

Internet Message Access Protocol supports server-hosted mailbox access.

Question 145. What is FTP traditionally used for?

  1. File transfer between networked hosts
  2. Dynamic routing
  3. Wireless authentication
  4. Time synchronization
Show correct answer and explanation

Correct answer: A. File transfer between networked hosts

File Transfer Protocol defines a client-server file exchange method.

Question 146. What does SFTP commonly run over?

  1. FTP control connection
  2. SSH
  3. ICMP
  4. ARP
Show correct answer and explanation

Correct answer: B. SSH

SFTP is the SSH File Transfer Protocol subsystem.

Question 147. What is a URL?

  1. A 48-bit link address
  2. A CPU instruction
  3. A locator identifying a resource and an access scheme
  4. A mandatory IPv6 extension
Show correct answer and explanation

Correct answer: C. A locator identifying a resource and an access scheme

Uniform Resource Locators contain scheme and resource-location information.

Question 148. What does a DNS recursive resolver do?

  1. Assign Ethernet addresses physically
  2. Manage CPU registers
  3. Create web server HTML
  4. Obtain DNS answers on behalf of clients using cache and upstream queries
Show correct answer and explanation

Correct answer: D. Obtain DNS answers on behalf of clients using cache and upstream queries

Recursive resolvers follow referrals and cache responses.

Question 149. What is DNSSEC designed to add?

  1. Origin authentication and integrity for DNS data
  2. Encryption of all DNS traffic
  3. Network address translation
  4. Wi-Fi radio security
Show correct answer and explanation

Correct answer: A. Origin authentication and integrity for DNS data

DNSSEC signs DNS data so validating resolvers can detect tampering.

Question 150. What does DNS over HTTPS commonly use to carry DNS requests?

  1. Plain FTP
  2. HTTPS
  3. Ethernet broadcasts only
  4. SMTP
Show correct answer and explanation

Correct answer: B. HTTPS

DoH encapsulates DNS queries and responses in HTTPS.

Computer Networks MCQs — Set 4 (Questions 151–200)

Read each question and reveal the correct answer and explanation.

Question 151. What is a firewall primarily used for?

  1. Assigning hostnames
  2. Boosting radio power
  3. Filtering network traffic according to security policy
  4. Converting IPv4 addresses into MAC addresses
Show correct answer and explanation

Correct answer: C. Filtering network traffic according to security policy

Firewalls enforce rules on permitted and denied traffic.

Question 152. What does a stateful firewall track?

  1. Only cable length
  2. Database row identifiers
  3. The color of Ethernet connectors
  4. Connection or flow state
Show correct answer and explanation

Correct answer: D. Connection or flow state

Stateful filtering considers established communication context.

Question 153. What does an intrusion detection system primarily do?

  1. Monitor activity for signs of attacks
  2. Always block all network access
  3. Replace the operating system
  4. Allocate DHCP leases
Show correct answer and explanation

Correct answer: A. Monitor activity for signs of attacks

An IDS detects and reports potentially malicious activity.

Question 154. How does an intrusion prevention system differ from passive detection?

  1. It cannot inspect packets
  2. It can take action to block or prevent detected threats
  3. It only names DNS records
  4. It always runs on a switch chip
Show correct answer and explanation

Correct answer: B. It can take action to block or prevent detected threats

An IPS can intervene in traffic while detecting threats.

Question 155. What is a VPN commonly used for?

  1. Replacing every routing protocol
  2. Increasing a physical wire’s speed
  3. Establishing a protected logical connection over another network
  4. Converting applications into processes
Show correct answer and explanation

Correct answer: C. Establishing a protected logical connection over another network

VPNs tunnel traffic and may protect it cryptographically.

Question 156. Which protocol suite can protect IP packets at the network layer?

  1. SMTP
  2. FTP
  3. DHCP
  4. IPsec
Show correct answer and explanation

Correct answer: D. IPsec

Internet Protocol Security provides authentication and encryption services for IP traffic.

Question 157. What is the purpose of an IPsec Security Association?

  1. Specify cryptographic parameters for protected traffic in one direction
  2. Choose an Ethernet cable
  3. Allocate a TCP port permanently
  4. Store an HTTP cookie
Show correct answer and explanation

Correct answer: A. Specify cryptographic parameters for protected traffic in one direction

SAs define algorithms, keys and related parameters for IPsec processing.

Question 158. What type of attack attempts to overwhelm a service using high-volume traffic?

  1. Domain registration
  2. Denial-of-service attack
  3. ARP cache maintenance
  4. Network time synchronization
Show correct answer and explanation

Correct answer: B. Denial-of-service attack

DoS attacks seek to exhaust service or network capacity.

Question 159. What does DDoS stand for?

  1. Dynamic Data Delivery on Switches
  2. Direct Domain Directory of Servers
  3. Distributed Denial of Service
  4. Dual Datagram Distribution Service
Show correct answer and explanation

Correct answer: C. Distributed Denial of Service

DDoS uses multiple sources to disrupt availability.

Question 160. What is ARP spoofing?

  1. Translating URLs into IPs
  2. Dividing IPv6 prefixes
  3. Selecting a TCP congestion window
  4. Sending forged ARP information to misdirect local traffic
Show correct answer and explanation

Correct answer: D. Sending forged ARP information to misdirect local traffic

Fake ARP replies can poison neighbors’ address mappings.

Question 161. What is DNS cache poisoning?

  1. Introducing false name-resolution data into a resolver cache
  2. Changing a subnet mask intentionally
  3. Installing a trusted certificate
  4. A normal TTL expiry
Show correct answer and explanation

Correct answer: A. Introducing false name-resolution data into a resolver cache

Poisoning can redirect name lookups to an attacker-controlled address.

Question 162. What is the security principle behind zero trust?

  1. Trust every internal host automatically
  2. Evaluate and authorize each access request rather than assuming network location is trusted
  3. Disable authentication inside LANs
  4. Allow all encrypted packets without inspection
Show correct answer and explanation

Correct answer: B. Evaluate and authorize each access request rather than assuming network location is trusted

Zero-trust approaches continuously validate access conditions.

Question 163. Which Wi-Fi security generation supports SAE in personal authentication?

  1. WEP
  2. Open Wi-Fi without encryption
  3. WPA3-Personal
  4. WPA1 with TKIP only
Show correct answer and explanation

Correct answer: C. WPA3-Personal

WPA3-Personal uses Simultaneous Authentication of Equals.

Question 164. Why is WEP not recommended for securing wireless LANs?

  1. It requires IPv6
  2. It cannot transmit Ethernet frames
  3. It always uses HTTPS
  4. Its design has known practical cryptographic weaknesses
Show correct answer and explanation

Correct answer: D. Its design has known practical cryptographic weaknesses

WEP can be broken with well-known attacks and should not protect modern WLANs.

Question 165. What is a man-in-the-middle attack?

  1. Interception or alteration of communication between parties
  2. A routing table backup
  3. A normal DHCP renewal
  4. A CPU scheduling conflict
Show correct answer and explanation

Correct answer: A. Interception or alteration of communication between parties

An intermediary can impersonate or interfere with communicating peers.

Question 166. What is a nonce in security protocols?

  1. A fixed DNS name
  2. A value intended for limited or one-time use to support freshness
  3. A packet’s physical size
  4. An Ethernet MAC prefix
Show correct answer and explanation

Correct answer: B. A value intended for limited or one-time use to support freshness

Nonces help prevent replay and distinguish protocol sessions.

Question 167. Which technology commonly verifies a website server’s identity through certificates?

  1. ARP
  2. CSMA/CD
  3. TLS
  4. RIP
Show correct answer and explanation

Correct answer: C. TLS

TLS certificate validation authenticates the peer’s identity when correctly implemented.

Question 168. Why is certificate hostname validation important?

  1. It calculates network throughput
  2. It assigns a default route
  3. It chooses a radio channel
  4. It checks that a certificate corresponds to the requested service name
Show correct answer and explanation

Correct answer: D. It checks that a certificate corresponds to the requested service name

Trusting a certificate for the wrong hostname can enable impersonation.

Question 169. What is a network proxy?

  1. An intermediary that forwards or processes requests on behalf of clients or servers
  2. An IPv4 subnet mask
  3. A MAC address factory
  4. A CPU register
Show correct answer and explanation

Correct answer: A. An intermediary that forwards or processes requests on behalf of clients or servers

Proxies relay traffic and may implement filtering or caching.

Question 170. What is a reverse proxy?

  1. A device translating electrical to optical signals only
  2. An intermediary that accepts client requests and forwards them to backend servers
  3. A loopback address
  4. A local host password
Show correct answer and explanation

Correct answer: B. An intermediary that accepts client requests and forwards them to backend servers

Reverse proxies front services for routing, load balancing and protection.

Question 171. What does a load balancer do?

  1. Create only one DNS record
  2. Change IPv4 to IPv6 without translation
  3. Distribute incoming work among backend services
  4. Force every packet on one link
Show correct answer and explanation

Correct answer: C. Distribute incoming work among backend services

Load balancers route requests to suitable backends.

Question 172. What is a content delivery network (CDN)?

  1. A single local disk cache
  2. A routing loop protocol
  3. A type of TCP checksum
  4. A geographically distributed network of servers serving content
Show correct answer and explanation

Correct answer: D. A geographically distributed network of servers serving content

CDNs bring content nearer users to reduce delivery latency.

Question 173. What does anycast addressing enable?

  1. Multiple nodes advertise the same destination address and routing selects a reachable instance
  2. One endpoint to reach every link-layer device automatically
  3. Multiple TCP ports to become one
  4. Only broadcast delivery
Show correct answer and explanation

Correct answer: A. Multiple nodes advertise the same destination address and routing selects a reachable instance

Anycast uses routing to direct traffic to one of several service nodes.

Question 174. What is multicast communication?

  1. Delivery to one receiver only
  2. Delivery to a subscribed group of receivers
  3. Delivery to all Internet devices
  4. Delivery without addressing
Show correct answer and explanation

Correct answer: B. Delivery to a subscribed group of receivers

Multicast targets interested members of a group.

Question 175. What is unicast?

  1. Delivery to every host on a subnet
  2. Transmission only through satellites
  3. Communication to one addressed destination
  4. Communication with no address
Show correct answer and explanation

Correct answer: C. Communication to one addressed destination

Unicast sends to an individually addressed recipient.

Question 176. What is network QoS?

  1. A method to create MAC addresses
  2. A DNS alias record
  3. A physical plug type
  4. Mechanisms to manage service characteristics such as delay and loss
Show correct answer and explanation

Correct answer: D. Mechanisms to manage service characteristics such as delay and loss

Quality of Service policies can prioritize or manage traffic treatment.

Question 177. What is traffic shaping?

  1. Controlling transmission timing and rate to meet a traffic profile
  2. Deleting packets randomly without policy
  3. Assigning network names
  4. Removing frame headers
Show correct answer and explanation

Correct answer: A. Controlling transmission timing and rate to meet a traffic profile

Shaping buffers or schedules packets to smooth traffic rates.

Question 178. What is traffic policing?

  1. Increasing every link’s physical rate
  2. Enforcing a traffic-rate policy by marking or dropping excess traffic
  3. Creating TLS certificates
  4. Resolving DNS queries
Show correct answer and explanation

Correct answer: B. Enforcing a traffic-rate policy by marking or dropping excess traffic

Policing checks conformance and may act on excess packets.

Question 179. Which field supports differentiated services markings in IP packets?

  1. TCP source port only
  2. Ethernet FCS
  3. DSCP
  4. ARP operation code
Show correct answer and explanation

Correct answer: C. DSCP

Differentiated Services Code Point indicates a traffic treatment class.

Question 180. What does ECN permit where supported?

  1. Converting TCP to Ethernet
  2. Suppressing every retransmission
  3. Replacing IP addresses with hostnames
  4. Signaling congestion without necessarily dropping packets
Show correct answer and explanation

Correct answer: D. Signaling congestion without necessarily dropping packets

Explicit Congestion Notification marks packets to indicate congestion.

Question 181. Why are buffers used in switches and routers?

  1. To hold packets briefly while awaiting processing or transmission
  2. To translate web domains permanently
  3. To replace routing tables
  4. To eliminate packet loss in all conditions
Show correct answer and explanation

Correct answer: A. To hold packets briefly while awaiting processing or transmission

Queues absorb transient contention but can overflow.

Question 182. What is bufferbloat?

  1. A larger-than-normal DNS name
  2. Excessive queuing delay due to large or poorly managed buffers
  3. A corrupted Ethernet connector
  4. A subnet mask error
Show correct answer and explanation

Correct answer: B. Excessive queuing delay due to large or poorly managed buffers

Oversized queues can increase latency even when throughput remains high.

Question 183. What is active queue management?

  1. A protocol for assigning IP addresses
  2. An FTP server type
  3. A strategy that signals or drops packets before queues become excessively full
  4. A Wi-Fi password standard
Show correct answer and explanation

Correct answer: C. A strategy that signals or drops packets before queues become excessively full

AQM methods manage congestion by proactively controlling queues.

Question 184. What is a network tunnel?

  1. A physically buried cable only
  2. A CPU pipeline stage
  3. A permanent DNS alias
  4. Encapsulating packets of one protocol within another
Show correct answer and explanation

Correct answer: D. Encapsulating packets of one protocol within another

Tunneling carries encapsulated traffic across an intervening network.

Question 185. What is GRE commonly used for?

  1. Generic packet encapsulation and tunneling
  2. Encrypting data by itself
  3. Allocating DNS domains
  4. Authenticating Wi-Fi clients
Show correct answer and explanation

Correct answer: A. Generic packet encapsulation and tunneling

GRE encapsulates different network-layer packets but does not itself provide encryption.

Question 186. What is the basic role of MPLS labels?

  1. Assign TCP sequence numbers
  2. Guide forwarding through a label-switched network
  3. Encrypt HTTP bodies
  4. Replace every physical MAC address
Show correct answer and explanation

Correct answer: B. Guide forwarding through a label-switched network

MPLS forwards using labels along label-switched paths.

Question 187. What is software-defined networking (SDN)?

  1. Prohibiting all software in networking
  2. Using only analog signaling
  3. Separating programmable network control from forwarding functions to varying degrees
  4. A single Ethernet collision domain
Show correct answer and explanation

Correct answer: C. Separating programmable network control from forwarding functions to varying degrees

SDN exposes programmable control over network forwarding behavior.

Question 188. What is an SDN controller?

  1. A physical fiber core
  2. A DNS TXT record
  3. A UDP checksum
  4. Software that coordinates or programs network behavior
Show correct answer and explanation

Correct answer: D. Software that coordinates or programs network behavior

Controllers manage network state and install policies or forwarding rules.

Question 189. What is network function virtualization (NFV)?

  1. Running network functions as software on virtualized infrastructure
  2. Replacing all routers with cables
  3. Guaranteeing no packet loss
  4. Eliminating network protocols
Show correct answer and explanation

Correct answer: A. Running network functions as software on virtualized infrastructure

NFV decouples functions such as firewalls from dedicated appliances.

Question 190. What is telemetry in network operations?

  1. Replacing packets with emails
  2. Collecting operational measurements and events
  3. Deleting every router log
  4. A subnet prefix only
Show correct answer and explanation

Correct answer: B. Collecting operational measurements and events

Telemetry reports metrics, logs or traces for visibility.

Question 191. What does SNMP stand for?

  1. Secure Network Mail Port
  2. Switch Name Mapping Program
  3. Simple Network Management Protocol
  4. Shared Network Memory Protocol
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Correct answer: C. Simple Network Management Protocol

SNMP supports monitoring and management of network devices.

Question 192. Which service is commonly used to collect and analyze network device log messages?

  1. ARP
  2. ICMP Echo
  3. DHCP lease renewal
  4. Syslog
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Correct answer: D. Syslog

Syslog is a standard approach for event message collection.

Question 193. What is packet capture?

  1. Recording packets traversing an interface for inspection
  2. Cloning an entire disk
  3. Allocating IP blocks
  4. Removing MAC addresses
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Correct answer: A. Recording packets traversing an interface for inspection

Packet capture supports troubleshooting and analysis.

Question 194. What does a packet sniffer do?

  1. Increase physical transmission speed
  2. Observe and inspect packets available on a network interface
  3. Issue DNS root certificates
  4. Replace a switch fabric
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Correct answer: B. Observe and inspect packets available on a network interface

Sniffers examine network traffic, subject to visibility and permissions.

Question 195. What is a network baseline?

  1. The lowest IPv4 address always
  2. Only the first router hop
  3. A reference description of normal performance or behavior
  4. A permanent absence of failures
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Correct answer: C. A reference description of normal performance or behavior

Baselines help detect deviations in traffic and system health.

Question 196. Why is network redundancy important?

  1. It guarantees zero downtime
  2. It removes all security risks
  3. It makes routing unnecessary
  4. It reduces dependence on a single component or path
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Correct answer: D. It reduces dependence on a single component or path

Redundant links or devices can maintain service during selected failures.

Question 197. What is an SLA in network services?

  1. Service Level Agreement
  2. Signal Length Allocation
  3. Secure LAN Address
  4. Switch Link Algorithm
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Correct answer: A. Service Level Agreement

An SLA defines agreed service commitments and metrics.

Question 198. Which measurement is most relevant to interactive voice call quality?

  1. Only disk capacity
  2. Latency, jitter and packet loss
  3. Only SQL query size
  4. Only file extension length
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Correct answer: B. Latency, jitter and packet loss

Real-time audio is sensitive to delay variation and losses.

Question 199. Why can TCP perform poorly for certain real-time interactive media if used without suitable design?

  1. TCP does not support ports
  2. TCP cannot use IP
  3. Retransmission and ordered delivery may increase delay during loss
  4. TCP never controls congestion
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Correct answer: C. Retransmission and ordered delivery may increase delay during loss

TCP’s reliability behavior may introduce head-of-line delays for time-sensitive data.

Question 200. What distinguishes network reliability from mere connectivity?

  1. A cable being present at one moment
  2. An IP address having four octets
  3. An application always using TCP
  4. Continued correct service despite relevant failures and loss conditions
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Correct answer: D. Continued correct service despite relevant failures and loss conditions

Reliability evaluates sustained delivery and availability under operating conditions.

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