Introduction
Data Communication and Computer Networking is a core topic in Computer Science exams, including PPSC, NTS, FPSC, and university entrance tests. Understanding key concepts like the OSI model layers, TCP/IP protocol suite, IP addressing, subnetting, and network security is crucial to securing high marks in these competitive tests.
This comprehensive guide on mcqsdesk.com features 50 carefully selected Networking MCQs with answers and clear explanations to strengthen your preparation.
Section 1: Network Basics & Topologies
Q1. Which layer of the OSI model is responsible for end-to-end communication and error recovery?
A) Network Layer
B) Transport Layer
C) Data Link Layer
D) Physical Layer
Answer: B) Transport Layer
Explanation: The Transport Layer (Layer 4) ensures reliable end-to-end data transfer, flow control, and error recovery using protocols like TCP.
Q2. In which network topology are all devices connected to a single central cable?
A) Star Topology
B) Ring Topology
C) Bus Topology
D) Mesh Topology
Answer: C) Bus Topology
Explanation: Bus topology utilizes a single main cable (backbone) to connect all network nodes.
Q3. Which network device operates at the Data Link Layer (Layer 2) of the OSI model?
A) Router
B) Switch
C) Hub
D) Repeater
Answer: B) Switch
Explanation: Switches operate at Layer 2 and use MAC addresses to forward data frames to specific target devices.
Q4. What is the full form of MAC address?
A) Media Access Control
B) Memory Access Center
C) Main Network Controller
D) Media Allocation Code
Answer: A) Media Access Control
Explanation: MAC address is a unique 48-bit hardware identifier assigned to a Network Interface Card (NIC) at the factory.
Q5. Which device amplifies and regenerates signals to extend network transmission distances?
A) Switch
B) Router
C) Repeater
D) Gateway
Answer: C) Repeater
Explanation: Repeaters operate at the Physical Layer (Layer 1) to clean and amplify attenuated signals over long cable lengths.
Section 2: OSI & TCP/IP Reference Models
Q6. How many layers are present in the standard OSI Reference Model?
A) 4
B) 5
C) 7
D) 6
Answer: C) 7
Explanation: The OSI model consists of 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Q7. Which OSI layer is responsible for data encryption, compression, and translation?
A) Application Layer
B) Presentation Layer
C) Session Layer
D) Transport Layer
Answer: B) Presentation Layer
Explanation: The Presentation Layer (Layer 6) handles syntax formatting, data compression, and encryption/decryption routines.
Q8. The process of adding headers and trailers to data as it moves down the OSI layers is called:
A) Decapsulation
B) Encapsulation
C) Segmentation
D) Multiplexing
Answer: B) Encapsulation
Explanation: Encapsulation wraps application data with control information (headers/trailers) at each layer before transmission.
Q9. Data unit at the Transport Layer in TCP is called a:
A) Frame
B) Packet
C) Segment
D) Bit
Answer: C) Segment
Explanation: Transport Layer PDUs are called Segments in TCP (and Datagrams in UDP). Packets belong to the Network Layer, and Frames belong to the Data Link Layer.
Q10. Which protocol suite serves as the practical foundation of the modern Internet?
A) OSI Model
B) TCP/IP Model
C) AppleTalk
D) IPX/SPX
Answer: B) TCP/IP Model
Explanation: TCP/IP (Transmission Control Protocol/Internet Protocol) is the standard communications architecture utilized globally across the Internet.
Section 3: IP Addressing & Subnetting
Q11. What is the length of an IPv4 address?
A) 128 bits
B) 64 bits
C) 32 bits
D) 16 bits
Answer: C) 32 bits
Explanation: An IPv4 address consists of 32 binary bits divided into four 8-bit octets expressed in dotted-decimal format.
Q12. What is the total length of an IPv6 address?
A) 32 bits
B) 64 bits
C) 128 bits
D) 256 bits
Answer: C) 128 bits
Explanation: IPv6 uses 128-bit addresses represented in hexadecimal notation to provide a vastly larger address space.
Q13. Which class of IPv4 addresses is reserved for Multicasting?
A) Class A
B) Class B
C) Class C
D) Class D
Answer: D) Class D
Explanation: Class D IP addresses (ranging from 224.0.0.0 to 239.255.255.255) are strictly allocated for multicast groups.
Q14. What is the default subnet mask for a Class B IPv4 network?
A) 255.0.0.0
B) 255.255.0.0
C) 255.255.255.0
D) 255.255.255.255
Answer: B) 255.255.0.0
Explanation: Class B default subnet mask uses 16 bits for the network portion (255.255.0.0 or /16).
Q15. Loopback IP address used for testing local network interfaces is:
A) 192.168.1.1
B) 127.0.0.1
C) 10.0.0.1
D) 255.255.255.255
Answer: B) 127.0.0.1
Explanation: The IPv4 range 127.0.0.0/8 (commonly 127.0.0.1) is reserved for internal system diagnostic loopback tests.
Section 4: Network Protocols & Ports
Q16. Which network protocol automatically assigns dynamic IP addresses to host devices?
A) DNS
B) DHCP
C) ARP
D) ICMP
Answer: B) DHCP
Explanation: Dynamic Host Configuration Protocol (DHCP) automatically manages and distributes IP addresses and gateway configurations.
Q17. Which protocol translates human-readable domain names (e.g., mcqsdesk.com) into IP addresses?
A) HTTP
B) DNS
C) FTP
D) SNMP
Answer: B) DNS
Explanation: Domain Name System (DNS) maps domain names to numerical IP addresses required for network routing.
Q18. What is the default port number used by secure web traffic via HTTPS?
A) 80
B) 21
C) 443
D) 25
Answer: C) 443
Explanation: HTTPS runs over port 443 with TLS/SSL encryption, whereas unencrypted HTTP uses port 80.
Q19. Address Resolution Protocol (ARP) is used to map an:
A) IP address to a MAC address
B) MAC address to an IP address
C) Domain name to an IP address
D) IP address to a Port number
Answer: A) IP address to a MAC address
Explanation: ARP resolves a known logical IP address (Layer 3) to its corresponding physical MAC address (Layer 2).
Q20. Which protocol operates connectionlessly and does not guarantee reliable packet delivery?
A) TCP
B) UDP
C) HTTP
D) SSH
Answer: B) UDP
Explanation: User Datagram Protocol (UDP) is a connectionless protocol prioritizing speed over delivery confirmation.
Q21. Which error reporting protocol is used by the ping utility?
A) IGMP
B) ICMP
C) SMTP
D) ARP
Answer: B) ICMP
Explanation: Internet Control Message Protocol (ICMP) sends diagnostic messages, echo requests, and error notifications.
Section 5: Transmission Media & Switching
Q22. Which guided transmission medium offers the highest data speeds and immunity to electromagnetic interference?
A) Coaxial Cable
B) Twisted Pair Cable
C) Fiber Optic Cable
D) Shielded Twisted Pair (STP)
Answer: C) Fiber Optic Cable
Explanation: Fiber optic cables transmit data via light pulses inside glass fibers, eliminating electromagnetic interference.
Q23. Unshielded Twisted Pair (UTP) cables commonly use which modular connector?
A) BNC
B) RJ45
C) DB9
D) SC Connector
Answer: B) RJ45
Explanation: Standard Ethernet patch cables with UTP wires use 8-pin RJ45 modular connectors.
Q24. Which switching technique breaks messages into fixed/variable blocks transmitted independently across nodes?
A) Circuit Switching
B) Packet Switching
C) Message Switching
D) Line Switching
Answer: B) Packet Switching
Explanation: Modern IP networks rely on packet switching to chunk data into individual packets routed dynamically across paths.
Q25. A dedicated physical communication channel established before data transfer begins is characteristic of:
A) Packet Switching
B) Circuit Switching
C) Frame Relay
D) Virtual Circuit Switching
Answer: B) Circuit Switching
Explanation: Traditional telephone networks use circuit switching to reserve an exclusive continuous path for the duration of a session.
Section 6: Data Link Control & Error Handling
Q26. Which medium access control protocol is used in legacy Ethernet networks to manage collisions?
A) CSMA/CA
B) CSMA/CD
C) Token Passing
D) Slotted ALOHA
Answer: B) CSMA/CD
Explanation: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) monitors cable traffic and manages simultaneous collision retransmissions.
Q27. Wireless networks (Wi-Fi 802.11) use which channel access mechanism?
A) CSMA/CD
B) CSMA/CA
C) Polling
D) FDMA
Answer: B) CSMA/CA
Explanation: Wireless nodes cannot reliably detect collisions while transmitting, so they use Collision Avoidance (CSMA/CA) with handshake signals.
Q28. Which error-detection code uses polynomial division to verify frame integrity?
A) Parity Check
B) Checksum
C) Cyclic Redundancy Check (CRC)
D) Hamming Code
Answer: C) Cyclic Redundancy Check (CRC)
Explanation: CRC computes a mathematical remainder value stored at the end of frames to identify bit corruption.
Q29. Flow control technique where the sender waits for an acknowledgment after sending each individual frame is:
A) Sliding Window
B) Stop-and-Wait ARQ
C) Go-Back-N ARQ
D) Selective Repeat ARQ
Answer: B) Stop-and-Wait ARQ
Explanation: Stop-and-Wait holds further transmissions until the receiving end explicitly acknowledges receipt of the current frame.
Q30. What is the full form of MTU in networking?
A) Maximum Transmission Unit
B) Minimum Transport Utility
C) Main Terminal Unit
D) Media Transmission Unicast
Answer: A) Maximum Transmission Unit
Explanation: MTU specifies the largest data packet size (in bytes) a network interface can process without fragmentation.
Section 7: Network Security & Devices
Q31. A software or hardware system that filters incoming and outgoing network traffic based on security rules is a:
A) Router
B) Bridge
C) Firewall
D) Modem
Answer: C) Firewall
Explanation: Firewalls monitor and control network traffic parameters to block unauthorized connections.
Q32. What type of attack floods a server with massive fake request traffic to crash services?
A) Man-in-the-Middle (MitM)
B) Denial of Service (DoS) / DDoS
C) Phishing
D) SQL Injection
Answer: B) Denial of Service (DoS) / DDoS
Explanation: DoS/DDoS attacks exhaust target server bandwidth and CPU resources, rendering services unavailable to real users.
Q33. Which network protocol provides encrypted remote shell terminal access?
A) Telnet
B) SSH
C) FTP
D) TFTP
Answer: B) SSH
Explanation: Secure Shell (SSH) uses port 22 to establish encrypted command-line management sessions, replacing insecure Telnet.
Q34. Virtual Private Network (VPN) creates a secure connection by establishing a:
A) Physical cable connection
B) Encrypted tunnel over a public network
C) Direct satellite link
D) Local VLAN switch loop
Answer: B) Encrypted tunnel over a public network
Explanation: VPNs protect privacy by routing network traffic through an encrypted virtual tunnel over open networks like the Internet.
Q35. A network device that translates analog signals from telephone lines into digital computer data is a:
A) Gateway
B) Modem
C) Hub
D) Multiplexer
Answer: B) Modem
Explanation: Modem stands for Modulator-Demodulator, converting between digital pulses and continuous analog signals.
Section 8: Advanced Networking Concepts
Q36. What is the primary purpose of Network Address Translation (NAT)?
A) To speed up web browsing
B) To map private internal IP addresses to a public IP address
C) To encrypt file downloads
D) To convert IPv4 addresses to IPv6
Answer: B) To map private internal IP addresses to a public IP address
Explanation: NAT allows multiple devices on a private local network to share a single public IP address, conserving IPv4 addresses.
Q37. Which routing algorithm uses the Distance Vector mechanism to find optimal paths?
A) OSPF
B) RIP
C) BGP
D) IS-IS
Answer: B) RIP
Explanation: Routing Information Protocol (RIP) uses Distance Vector based on hop counts, whereas OSPF uses Link-State algorithms.
Q38. What is the maximum number of hops allowed in RIP (Routing Information Protocol)?
A) 10
B) 15
C) 30
D) 255
Answer: B) 15
Explanation: RIP considers a metric of 16 as unreachable (infinity), limiting valid network paths to 15 hops.
Q39. Which interior gateway protocol uses Link-State logic for large enterprise networks?
A) RIP
B) OSPF
C) EGP
D) BGP
Answer: B) OSPF
Explanation: Open Shortest Path First (OSPF) builds a complete topological map of the network using Dijkstra’s algorithm.
Q40. Border Gateway Protocol (BGP) is classified as an:
A) Interior Gateway Protocol (IGP)
B) Exterior Gateway Protocol (EGP)
C) Application Protocol
D) Data Link Protocol
Answer: B) Exterior Gateway Protocol (EGP)
Explanation: BGP routes data across different Autonomous Systems (AS) connecting major Internet Service Providers.
Q41. What is the default subnet mask for a Class A network?
A) 255.0.0.0
B) 255.255.0.0
C) 255.255.255.0
D) 255.255.255.255
Answer: A) 255.0.0.0
Explanation: Class A networks reserve the first 8 bits for the network ID (255.0.0.0 or /8).
Q42. Which wireless standard operates at 2.4 GHz and 5 GHz frequency bands with speeds up to multi-Gbps?
A) IEEE 802.3
B) IEEE 802.11
C) IEEE 802.15
D) IEEE 802.1
Answer: B) IEEE 802.11
Explanation: The IEEE 802.11 working group defines standard protocols for Wireless Local Area Networks (Wi-Fi).
Q43. What is a VLAN (Virtual Local Area Network)?
A) A physical cabling standard
B) A logical grouping of network devices created regardless of physical location
C) An encryption key standard
D) A wireless access point model
Answer: B) A logical grouping of network devices created regardless of physical location
Explanation: VLANs segment physical switch networks into separate isolated logical broadcast domains.
Q44. Which protocol handles simple network management and device status monitoring?
A) SMTP
B) SNMP
C) POP3
D) IMAP
Answer: B) SNMP
Explanation: Simple Network Management Protocol (SNMP) collects performance data and monitors routers, switches, and servers.
Q45. Time to Live (TTL) field in an IPv4 header is used to:
A) Record round-trip response time
B) Prevent packets from circulating indefinitely in routing loops
C) Measure bandwidth throughput
D) Timestamp packet transmission
Answer: B) Prevent packets from circulating indefinitely in routing loops
Explanation: TTL decrements by 1 at each router hop; if TTL reaches zero, the packet is discarded with an ICMP message.
Q46. What is the standard port number for File Transfer Protocol (FTP) control connection?
A) 20
B) 21
C) 22
D) 23
Answer: B) 21
Explanation: FTP uses port 21 to establish control connections and issue commands (port 20 carries data transfers).
Q47. Which multiplexing technique divides total frequency bandwidth into smaller non-overlapping sub-bands?
A) TDM (Time Division Multiplexing)
B) FDM (Frequency Division Multiplexing)
C) WDM
D) CDM
Answer: B) FDM (Frequency Division Multiplexing)
Explanation: FDM splits high-frequency radio or cable bandwidth into individual channels assigned to different signals.
Q48. What is the functional role of a Gateway in networking?
A) To connect networks with different protocol suites
B) To amplify electrical signals
C) To store web pages locally
D) To allocate MAC addresses
Answer: A) To connect networks with different protocol suites
Explanation: Gateways operate across upper layers to translate formats between dissimilar network architectures.
Q49. Which command-line utility displays active TCP connections and listening ports on a host?
A) ipconfig
B) netstat
C) nslookup
D) traceroute
Answer: B) netstat
Explanation: netstat (network statistics) prints socket connections, routing tables, and interface metrics.
Q50. Which protocol provides email delivery service between servers across the Internet?
A) POP3
B) IMAP
C) SMTP
D) HTTP
Answer: C) SMTP
Explanation: Simple Mail Transfer Protocol (SMTP) handles outgoing mail routing between mail servers.
Conclusion
Mastering Data Communication and Computer Networking is vital for clearing screening exams like PPSC, NTS, and FPSC for Computer Science posts. Understanding layer functions, protocol ports, IP address classes, and security basics guarantees higher marks.
Keep practicing on mcqsdesk.com for more subject-specific MCQs with explanations to excel in your upcoming competitive tests!
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