Network MCQs (01-100)
Q1. What is the main function of the Transport Layer in the OSI model?
A) Routing packets
B) Error detection
C) End-to-end communication
D) Framing data
✅ Correct Answer: C
💡 Explanation: The Transport Layer ensures reliable end-to-end communication between devices, handling segmentation and error recovery.
Q2. Which OSI layer is responsible for converting data into electrical signals?
A) Application
B) Network
C) Physical
D) Data Link
✅ Correct Answer: C
💡 Explanation: The Physical Layer handles transmission of raw bitstreams over physical mediums such as cables and radio waves.
Q3. The OSI model has how many layers?
A) 5
B) 6
C) 7
D) 8
✅ Correct Answer: C
💡 Explanation: The OSI (Open Systems Interconnection) model consists of seven layers ranging from Physical to Application.
Q4. In the TCP/IP model, which layer corresponds to the OSI Transport Layer?
A) Network Interface
B) Internet
C) Transport
D) Application
✅ Correct Answer: C
💡 Explanation: The TCP/IP Transport Layer corresponds to the OSI Transport Layer and provides end-to-end data delivery services.
Q5. Which OSI layer adds a header that contains source and destination MAC addresses?
A) Network
B) Data Link
C) Transport
D) Session
✅ Correct Answer: B
💡 Explanation: The Data Link Layer adds MAC address information to frames for delivery within the same network.
Q6. What protocol operates at the OSI Network Layer?
A) TCP
B) IP
C) HTTP
D) ARP
✅ Correct Answer: B
💡 Explanation: The Internet Protocol (IP) operates at the Network Layer and is responsible for logical addressing and routing.
Q7. Which device operates at Layer 2 of the OSI model?
A) Router
B) Hub
C) Switch
D) Firewall
✅ Correct Answer: C
💡 Explanation: Switches operate at Layer 2 (Data Link), using MAC addresses to forward frames.
Q8. The Presentation Layer is responsible for:
A) Routing packets
B) Data encryption and formatting
C) Session control
D) Error detection
✅ Correct Answer: B
💡 Explanation: The Presentation Layer translates data into a usable format, handling encryption, compression, and encoding.
Q9. Which layer of the OSI model handles logical addressing?
A) Transport
B) Network
C) Data Link
D) Session
✅ Correct Answer: B
💡 Explanation: The Network Layer assigns IP addresses and determines the best path for data transmission.
Q10. Which topology connects each device to every other device in the network?
A) Bus
B) Ring
C) Mesh
D) Star
✅ Correct Answer: C
💡 Explanation: A Mesh topology provides redundant links by connecting every node directly to every other node.
Q11. What is a disadvantage of a bus topology?
A) Simple setup
B) Cost-effective
C) Single point of failure on the main cable
D) Easy to troubleshoot
✅ Correct Answer: C
💡 Explanation: In a bus topology, a fault in the main cable can bring down the entire network.
Q12. Which layer ensures reliable delivery of data using flow control and acknowledgments?
A) Data Link
B) Network
C) Transport
D) Session
✅ Correct Answer: C
💡 Explanation: The Transport Layer ensures reliable data delivery through mechanisms like TCP acknowledgments and flow control.
Q13. In a ring topology, data travels:
A) In both directions simultaneously
B) In one direction only
C) Randomly
D) To a central hub
✅ Correct Answer: B
💡 Explanation: In a ring topology, data travels in a single, predefined direction through each node until it reaches the destination.
Q14. Which protocol is connection-oriented?
A) UDP
B) IP
C) TCP
D) ICMP
✅ Correct Answer: C
💡 Explanation: TCP is a connection-oriented protocol that establishes a reliable connection before transmitting data.
Q15. The main function of the Network Layer is:
A) Reliable transmission
B) Physical signaling
C) Path determination and logical addressing
D) Data presentation
✅ Correct Answer: C
💡 Explanation: The Network Layer handles routing and IP addressing for efficient data delivery.
Q16. In the OSI model, which layer is responsible for data compression?
A) Presentation
B) Application
C) Transport
D) Session
✅ Correct Answer: A
💡 Explanation: The Presentation Layer performs data compression to optimize transmission and reduce bandwidth usage.
Q17. Which device operates at Layer 3 of the OSI model?
A) Switch
B) Router
C) Hub
D) Repeater
✅ Correct Answer: B
💡 Explanation: Routers operate at Layer 3, forwarding packets based on IP addresses.
Q18. What is encapsulation in networking?
A) Adding headers and trailers to data as it moves down OSI layers
B) Removing headers from data packets
C) Combining multiple packets into one
D) Encrypting data for security
✅ Correct Answer: A
💡 Explanation: Encapsulation refers to wrapping data with protocol information at each OSI layer.
Q19. Which topology uses a central device to connect all nodes?
A) Mesh
B) Bus
C) Ring
D) Star
✅ Correct Answer: D
💡 Explanation: A Star topology connects all devices to a central hub or switch, simplifying management.
Q20. The TCP/IP model has how many layers?
A) 3
B) 4
C) 5
D) 7
✅ Correct Answer: B
💡 Explanation: The TCP/IP model has four layers: Network Interface, Internet, Transport, and Application.
Q21. Which OSI layer establishes, manages, and terminates sessions?
A) Session
B) Transport
C) Application
D) Network
✅ Correct Answer: A
💡 Explanation: The Session Layer manages sessions between communicating devices, maintaining and synchronizing dialogs.
Q22. In a star topology, if the central hub fails:
A) Only one node is affected
B) The entire network goes down
C) Data reroutes automatically
D) Nothing happens
✅ Correct Answer: B
💡 Explanation: The hub is the central connection point; if it fails, communication between all nodes stops.
Q23. Which OSI layer is responsible for translating network addresses to physical addresses?
A) Data Link
B) Network
C) Session
D) Physical
✅ Correct Answer: A
💡 Explanation: The Data Link Layer maps logical addresses to physical (MAC) addresses for local delivery.
Q24. What is the main purpose of the Application Layer in the OSI model?
A) Data translation
B) User interface and network services
C) Routing
D) Error correction
✅ Correct Answer: B
💡 Explanation: The Application Layer provides user-facing network services like email, file transfer, and web browsing.
Q25. The TCP protocol guarantees delivery by using:
A) Checksums only
B) Acknowledgments and retransmissions
C) Data compression
D) Encryption
✅ Correct Answer: B
Q26. Which class of IP address has a default subnet mask of 255.255.255.0?
A) Class A
B) Class B
C) Class C
D) Class D
✅ Correct Answer: C
💡 Explanation: Class C addresses use a default subnet mask of 255.255.255.0, allowing up to 254 hosts per network.
Q27. What is the binary equivalent of the IP address 192.168.1.1?
A) 10101100.00010000.00000001.00000001
B) 11000000.10101000.00000001.00000001
C) 11100000.00000000.00000001.00000001
D) 10000000.00001010.00000001.00000001
✅ Correct Answer: B
💡 Explanation: 192 = 11000000 and 168 = 10101000, so 192.168.1.1 becomes 11000000.10101000.00000001.00000001.
Q28. Which protocol is used to automatically assign IP addresses to hosts?
A) ARP
B) ICMP
C) DHCP
D) DNS
✅ Correct Answer: C
💡 Explanation: DHCP dynamically assigns IP addresses and other configuration details to network devices.
Q29. What is the range of a Class A IP address?
A) 0.0.0.0 – 127.255.255.255
B) 128.0.0.0 – 191.255.255.255
C) 192.0.0.0 – 223.255.255.255
D) 224.0.0.0 – 239.255.255.255
✅ Correct Answer: A
💡 Explanation: Class A addresses range from 0.0.0.0 to 127.255.255.255 and are used for very large networks.
Q30. Which address is reserved for loopback testing in IPv4?
A) 127.0.0.0
B) 127.0.0.1
C) 0.0.0.0
D) 255.255.255.255
✅ Correct Answer: B
💡 Explanation: 127.0.0.1 is the standard loopback address used to test a device’s TCP/IP stack.
Q31. What is the default subnet mask for a Class B network?
A) 255.0.0.0
B) 255.255.0.0
C) 255.255.255.0
D) 255.255.255.255
✅ Correct Answer: B
💡 Explanation: Class B addresses use the subnet mask 255.255.0.0, supporting up to 65,534 hosts per network.
Q32. Which IP address class supports multicast?
A) Class A
B) Class C
C) Class D
D) Class E
✅ Correct Answer: C
💡 Explanation: Class D (224.0.0.0–239.255.255.255) is reserved for multicast communication.
Q33. What does CIDR stand for?
A) Classless Internet Domain Routing
B) Classless Inter-Domain Routing
C) Centralized Internet Data Routing
D) Class Internet Domain Resolution
✅ Correct Answer: B
💡 Explanation: CIDR allows flexible IP address allocation and reduces routing table sizes by discarding rigid class boundaries.
Q34. The subnet mask 255.255.255.192 provides how many usable host addresses per subnet?
A) 32
B) 62
C) 64
D) 126
✅ Correct Answer: B
💡 Explanation: The subnet mask /26 leaves 6 host bits, giving 2⁶–2 = 62 usable host addresses.
Q35. What is the primary purpose of a router?
A) Connect computers within a LAN
B) Forward packets between different networks
C) Regenerate electrical signals
D) Resolve domain names
✅ Correct Answer: B
💡 Explanation: Routers operate at Layer 3 to forward packets between separate networks based on IP addresses.
Q36. Which protocol maps IP addresses to MAC addresses?
A) ARP
B) DHCP
C) DNS
D) ICMP
✅ Correct Answer: A
💡 Explanation: The Address Resolution Protocol (ARP) converts logical IP addresses to physical MAC addresses.
Q37. What is the broadcast address of the subnet 192.168.10.0/24?
A) 192.168.10.0
B) 192.168.10.1
C) 192.168.10.254
D) 192.168.10.255
✅ Correct Answer: D
💡 Explanation: In a /24 network, the broadcast address is the last address in the subnet, ending with .255.
Q38. Which protocol is used to find the route to a destination?
A) ARP
B) ICMP
C) OSPF
D) FTP
✅ Correct Answer: C
💡 Explanation: OSPF (Open Shortest Path First) is a dynamic routing protocol that finds optimal paths using link-state algorithms.
Q39. What is the maximum number of hosts in a /25 subnet?
A) 126
B) 128
C) 254
D) 256
✅ Correct Answer: A
💡 Explanation: A /25 mask leaves 7 bits for hosts: 2⁷–2 = 126 usable addresses.
Q40. Which command can display the IP configuration of a host in Windows?
A) ping
B) netstat
C) ipconfig
D) ifconfig
✅ Correct Answer: C
💡 Explanation: ipconfig displays IP configuration details on Windows systems.
Q41. In IPv6, which type of address is equivalent to IPv4’s private address?
A) Multicast
B) Link-local
C) Unique local
D) Global unicast
✅ Correct Answer: C
💡 Explanation: IPv6 unique local addresses (fc00::/7) serve as private network addresses similar to IPv4’s private ranges.
Q42. The default gateway in a network is used to:
A) Store DNS records
B) Resolve IP to MAC
C) Forward packets to other networks
D) Manage ARP cache
✅ Correct Answer: C
💡 Explanation: The default gateway routes traffic from a local network to external networks, such as the Internet.
Q43. What is the purpose of the subnet mask?
A) To identify the network and host portions of an IP address
B) To encrypt data packets
C) To compress network traffic
D) To convert IP to MAC
✅ Correct Answer: A
💡 Explanation: The subnet mask separates the network ID from the host ID in an IP address.
Q44. Which protocol provides error reporting for IP packets?
A) TCP
B) ICMP
C) ARP
D) SNMP
✅ Correct Answer: B
💡 Explanation: ICMP reports network errors and provides diagnostic functions like ping and traceroute.
Q45. The IP address 10.0.0.0 belongs to which class?
A) Class A
B) Class B
C) Class C
D) Class D
✅ Correct Answer: A
💡 Explanation: Addresses from 1.0.0.0 to 126.255.255.255 are Class A, including 10.0.0.0.
Q46. Which of the following is a valid IPv6 address?
A) 192.168.0.1
B) 2001:0db8:85a3:0000:0000:8a2e:0370:7334
C) 255.255.255.255
D) fe80-0000-0000-0000
✅ Correct Answer: B
💡 Explanation: IPv6 addresses are 128-bit written in hexadecimal separated by colons.
Q47. What does NAT stand for?
A) Network Allocation Table
B) Network Address Translation
C) Node Address Transfer
D) Name Allocation Transfer
✅ Correct Answer: B
💡 Explanation: NAT allows multiple private IP addresses to share a single public IP, conserving address space.
Q48. Which routing protocol uses hop count as its metric?
A) OSPF
B) EIGRP
C) RIP
D) BGP
✅ Correct Answer: C
💡 Explanation: RIP (Routing Information Protocol) uses hop count to determine the best path to a destination.
Q49. What is the loopback address range in IPv6?
A) fe80::/10
B) ::1/128
C) fc00::/7
D) ff00::/8
✅ Correct Answer: B
💡 Explanation: The IPv6 loopback address is ::1/128 and serves the same purpose as 127.0.0.1 in IPv4.
Q50. Which device connects multiple networks using IP addresses?
A) Bridge
B) Switch
C) Router
D) Hub
✅ Correct Answer: C
Q51. Which device operates at Layer 1 of the OSI model?
A) Router
B) Repeater
C) Switch
D) Bridge
✅ Correct Answer: B
Q52. A switch operates primarily at which OSI layer?
A) Data Link
B) Network
C) Transport
D) Application
✅ Correct Answer: A
Q53. What is the function of a bridge in a network?
A) Amplify signals
B) Connect different networks
C) Divide a network into segments
D) Translate addresses
✅ Correct Answer: C
Q54. A router uses which type of address for packet forwarding?
A) MAC address
B) IP address
C) Port number
D) Device name
✅ Correct Answer: B
Q55. What is the main advantage of using switches over hubs?
A) Cost
B) Reduced collisions
C) More power usage
D) More broadcast traffic
✅ Correct Answer: B
Q56. Which of the following devices operates at both Layer 2 and Layer 3?
A) Managed switch
B) Hub
C) Bridge
D) Repeater
✅ Correct Answer: A
Q57. VLANs are used to:
A) Increase bandwidth
B) Divide a network logically
C) Connect networks physically
D) Reduce IP address usage
✅ Correct Answer: B
Q58. Which device connects two dissimilar networks?
A) Switch
B) Router
C) Repeater
D) Hub
✅ Correct Answer: B
Q59. Port security is a feature found on:
A) Routers
B) Switches
C) Firewalls
D) Bridges
✅ Correct Answer: B
Q60. What type of switch forwards frames after receiving the entire frame?
A) Cut-through
B) Store-and-forward
C) Fragment-free
D) Adaptive
✅ Correct Answer: B
Q61. What type of network device prevents broadcasts from crossing boundaries?
A) Switch
B) Router
C) Bridge
D) Repeater
✅ Correct Answer: B
Q62. A Layer 3 switch combines the functions of:
A) Bridge and Hub
B) Router and Switch
C) Repeater and Bridge
D) Modem and Switch
✅ Correct Answer: B
Q63. What is the default VLAN on a Cisco switch?
A) VLAN 0
B) VLAN 1
C) VLAN 10
D) VLAN 100
✅ Correct Answer: B
Q64. Which network device can separate collision domains but not broadcast domains?
A) Hub
B) Switch
C) Router
D) Bridge
✅ Correct Answer: B
Q65. What does STP (Spanning Tree Protocol) prevent?
A) IP conflicts
B) Switching loops
C) Broadcast storms
D) Packet loss
✅ Correct Answer: B
Q66. A hub sends incoming traffic to:
A) The destination device only
B) All connected devices
C) The default gateway
D) Only active devices
✅ Correct Answer: B
Q67. Which type of address does a switch use to forward frames?
A) IP address
B) Port address
C) MAC address
D) Logical address
✅ Correct Answer: C
Q68. Which of the following is a Layer 7 device?
A) Router
B) Application firewall
C) Hub
D) Switch
✅ Correct Answer: B
Q69. A router maintains information in a:
A) MAC table
B) Routing table
C) ARP cache
D) Bridge table
✅ Correct Answer: B
Q70. The function of a repeater is to:
A) Filter traffic
B) Regenerate signals
C) Route packets
D) Translate addresses
✅ Correct Answer: B
Q71. What type of network device provides NAT functionality?
A) Router
B) Bridge
C) Switch
D) Hub
✅ Correct Answer: A
Q72. What is the primary function of a firewall?
A) Block viruses
B) Control network traffic
C) Encrypt data
D) Increase bandwidth
✅ Correct Answer: B
Q73. Which protocol is used by switches to communicate VLAN information?
A) OSPF
B) VTP
C) STP
D) ARP
✅ Correct Answer: B
Q74. What type of network device connects LANs to WANs?
A) Router
B) Hub
C) Bridge
D) Switch
✅ Correct Answer: A
Q75. What is the purpose of a Layer 2 loop guard?
A) Prevent IP conflicts
B) Prevent redundant links
C) Prevent broadcast storms
D) Detect unidirectional links
✅ Correct Answer: D