20 Computer Networking MCQs for NTS, CSS, PMS, KPPSC, PPSC, ETEA, SPSC, BPSC, and FPSC

Here is a comprehensive set of 20 Computer Networking Multiple Choice Questions (MCQs) for competitive exams like NTS, CSS, PMS, KPPSC, PPSC, ETEA, SPSC, BPSC, and FPSC.

These questions cover core networking concepts, including the OSI model, IP addressing, protocols, hardware, and network topologies.

1. How many layers are there in the OSI (Open Systems Interconnection) reference model?
A) 4
B) 5
C) 7
D) 9
Correct Answer: C

Explanation: The OSI model consists of 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

2. Which of the following protocols provides reliable, connection-oriented data delivery?
A) UDP
B) TCP
C) IP
D) ICMP
Correct Answer: B

Explanation: TCP (Transmission Control Protocol) is connection-oriented and ensures reliable data delivery through error checking and acknowledgment. UDP is connectionless and does not guarantee delivery.

3. What is the length of an IPv4 address?
A) 16 bits
B) 32 bits
C) 64 bits
D) 128 bits
Correct Answer: B

Explanation: An IPv4 address is 32 bits long, typically written in four decimal blocks (e.g., 192.168.1.1). IPv6 addresses are 128 bits long.

4. In which network topology do all devices connect to a central hub or switch?
A) Ring
B) Mesh
C) Bus
D) Star
Correct Answer: D

Explanation: In a Star topology, all nodes are connected to a central networking device. If a single cable fails, only that node goes down, but if the central device fails, the entire network drops.

5. Which port number is designated for the HTTP (Hypertext Transfer Protocol) by default?
A) 21
B) 25
C) 80
D) 443
Correct Answer: C

Explanation: HTTP operates on port 80. Port 443 is used for HTTPS (secure), Port 21 is for FTP, and Port 25 is for SMTP.

6. What is the size of a MAC (Media Access Control) address?
A) 24 bits
B) 32 bits
C) 48 bits
D) 64 bits
Correct Answer: C

Explanation: A MAC address is a 48-bit hardware address assigned to a network interface controller (NIC), usually represented as six pairs of hexadecimal digits.

7. Which IP address is reserved for loopback or local testing?
A) 192.168.0.1
B) 10.0.0.0
C) 127.0.0.1
D) 255.255.255.0
Correct Answer: C

Explanation: The address 127.0.0.1 is the standard loopback address used by a computer to send a message to itself for testing network software functionality.

8. Which hardware device operates at the Network Layer (Layer 3) of the OSI model?
A) Switch
B) Hub
C) Router
D) Repeater
Correct Answer: C

Explanation: Routers operate at the Network layer. They read IP addresses and determine the best path to forward data packets between different networks.

9. What protocol dynamically assigns IP addresses to devices on a network?
A) DNS
B) DHCP
C) ARP
D) FTP
Correct Answer: B

Explanation: DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses and other network configuration parameters to devices upon connection.

10. What is the primary function of the DNS (Domain Name System)?
A) To translate domain names into IP addresses
B) To securely transfer files
C) To route packets across the internet
D) To encrypt web traffic
Correct Answer: A

Explanation: DNS acts as the "phonebook" of the internet, translating human-readable domain names (like [www.google.com](https://www.google.com)) into machine-readable IP addresses.

11. What is the maximum theoretical cable length for an Unshielded Twisted Pair (UTP) Ethernet connection before a repeater is needed?
A) 50 meters
B) 100 meters
C) 200 meters
D) 500 meters
Correct Answer: B

Explanation: The maximum segment length for a standard UTP (like Cat5e or Cat6) Ethernet cable is 100 meters (about 328 feet) to prevent signal degradation.

12. Which command-line tool is used to test the reachability of a host on an IP network and measure round-trip time?
A) netstat
B) ipconfig
C) ping
D) tracert
Correct Answer: C

Explanation: The `ping` command sends ICMP Echo Request messages to a destination and waits for an Echo Reply to verify connectivity and latency.

13. Which layer of the OSI model is responsible for data encryption, decryption, and compression?
A) Application Layer
B) Presentation Layer
C) Session Layer
D) Transport Layer
Correct Answer: B

Explanation: The Presentation layer (Layer 6) formats, encrypts, and compresses data so it can be understood by the Application layer.

14. Which class of IP addresses is strictly reserved for Multicasting?
A) Class A
B) Class B
C) Class C
D) Class D
Correct Answer: D

Explanation: Class D IP addresses (ranging from 224.0.0.0 to 239.255.255.255) are not assigned to individual hosts; they are reserved for multicast groups.

15. What is the IEEE standard associated with Wireless LANs (Wi-Fi)?
A) IEEE 802.3
B) IEEE 802.5
C) IEEE 802.11
D) IEEE 802.15
Correct Answer: C

Explanation: IEEE 802.11 is the set of standards for implementing wireless local area networks (WLAN/Wi-Fi). 802.3 is for Ethernet.

16. Which protocol is primarily used for *sending* outgoing emails?
A) POP3
B) IMAP
C) SMTP
D) SNMP
Correct Answer: C

Explanation: SMTP (Simple Mail Transfer Protocol) is used to push/send emails from a client to a server. POP3 and IMAP are used to retrieve emails.

17. The Internet relies fundamentally on which type of switching technique?
A) Circuit switching
B) Message switching
C) Packet switching
D) Path switching
Correct Answer: C

Explanation: The internet uses packet switching, where data is broken down into small packets that independently navigate the network to reach their destination and are reassembled upon arrival.

18. What network security system monitors and controls incoming and outgoing network traffic based on predetermined security rules?
A) Antivirus
B) Proxy Server
C) Switch
D) Firewall
Correct Answer: D

Explanation: A firewall establishes a barrier between a trusted internal network and an untrusted external network (like the internet) based on security rules.

19. Which device is primarily used to connect two fundamentally *different* networks, often translating protocols between them?
A) Bridge
B) Switch
C) Gateway
D) Hub
Correct Answer: C

Explanation: A Gateway acts as a "door" between two different networks, converting protocols and formats if the networks use completely different architectures.

20. What does VPN stand for in networking?
A) Visual Processing Node
B) Virtual Private Network
C) Variable Packet Network
D) Virtual Public Network
Correct Answer: B

Explanation: A Virtual Private Network (VPN) extends a private network across a public network (like the internet), allowing users to send and receive data securely as if their computing devices were directly connected to the private network.