Networking and Cybersecurity MCQs with Explanations
Objective MCQs on the OSI model, TCP/IP addressing, standard ports, network devices and topologies, Wi-Fi bands and core security concepts, with explanations that clear up the usual confusions.
50
Questions
Exam-Level
Difficulty
4
Exams Covered
75
Min Time
Exam-Level PPSC FPSC NTS CSS
Last updated: Oct 13, 2026
50
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Q1 of 50
★ PPSC
★ NTS
In the OSI reference model, which numbered layer is the Transport layer?
Correct Answer: Option C — Fourth layer
Detailed Academic Explanation:
The layers from the bottom are Physical (1), Data Link (2), Network (3), Transport (4), Session (5), Presentation (6) and Application (7), so Transport is the fourth. The third layer is the Network layer, which is the most common wrong pick because it also deals with end-to-end delivery.
💡 Key Conceptual Anchor:
OSI model: seven layers in fixed order, with Transport (segment-level, TCP/UDP) above Network (packet-level, IP).
🎯 Examiner's Trap & Study Tip:
Mnemonic for the bottom-up order: 'Please Do Not Throw Sausage Pizza Away' - Transport is the fourth word, hence layer 4.
Q2 of 50
★ FPSC
★ PPSC
Which of the following device-to-OSI-layer pairings is correct?
Correct Answer: Option D — Router - network layer
Detailed Academic Explanation:
A router forwards packets at layer 3 using IP addresses, so that pairing is correct. A hub is a layer 1 repeater that floods signals to every port, while switches and bridges both work at layer 2 using MAC addresses, making the first three options wrong.
💡 Key Conceptual Anchor:
Device layers: hub and modem at Physical (1); bridge and switch at Data Link (2); router at Network (3).
🎯 Examiner's Trap & Study Tip:
Switches learn MAC addresses, routers learn IP addresses. A multi-layer switch that routes is called a layer 3 switch.
Q3 of 50
★ PPSC
★ NTS
Which transport-layer protocol is connectionless, guarantees neither delivery nor ordering, and is preferred for live voice and video?
Correct Answer: Option B — User Datagram Protocol (UDP)
Detailed Academic Explanation:
UDP sends datagrams without setting up a session or waiting for acknowledgements, so it is fast but unreliable - ideal for VoIP and streaming, where a late packet is worthless anyway. TCP is the reliable connection-oriented alternative, and FTP and HTTP are application-layer protocols that run over TCP.
💡 Key Conceptual Anchor:
TCP is reliable, ordered and connection-oriented; UDP is connectionless with no retransmission or ordering.
🎯 Examiner's Trap & Study Tip:
Real-time traffic (voice, video, DNS lookups) leans on UDP; anything that must arrive complete (files, web pages, mail) uses TCP.
Q4 of 50
★ PPSC
★ FPSC
How many bits are there in a complete IPv4 address?
Correct Answer: Option B — 32 bits
Detailed Academic Explanation:
An IPv4 address is 32 bits long and is written as four decimal octets, each 0-255. Class C networks cover first-octet values 192 to 223.
🎯 Examiner's Trap & Study Tip:
128 bits is the IPv6 answer — examiners offer it inside IPv4 questions to catch candidates who mix the two.
Q5 of 50
★ NTS
★ PPSC
Which port number and service pair is correct?
Correct Answer: Option C — 25 - SMTP
Detailed Academic Explanation:
Port 25 is SMTP, used for submitting mail. Port 21 is the FTP control channel, port 23 is Telnet, and port 22 is SSH, the encrypted replacement for Telnet remote login.
🎯 Examiner's Trap & Study Tip:
Group them: secure remote access 22, secure web 443, plain web 80, mail out 25 and mail in 110 or 143, name service 53.
Q6 of 50
★ PPSC
★ NTS
Which statement correctly describes the roles of DNS and DHCP?
Correct Answer: Option B — DNS resolves domain names into IP addresses while DHCP automatically assigns an IP address, subnet mask and gateway to a host
Detailed Academic Explanation:
DNS is the distributed directory that turns a name such as example.pk into an IP address (port 53), and DHCP leases the addressing configuration to devices as they join the network. The last option describes ARP, not DHCP, and browser encryption is the work of TLS over HTTPS.
💡 Key Conceptual Anchor:
DNS = name resolution on port 53; DHCP = automatic IP configuration using UDP ports 67 and 68.
🎯 Examiner's Trap & Study Tip:
If the stem says 'translate a name', choose DNS; 'hand out addresses' means DHCP; 'IP to MAC' means ARP.
Q7 of 50
★ FPSC
★ PPSC
Which network topology provides the highest fault tolerance because every device has a dedicated point-to-point link to every other device?
Correct Answer: Option D — Mesh topology
Detailed Academic Explanation:
A full mesh keeps redundant paths between all pairs of nodes, so no single link or node failure can isolate the network - the price is heavy cabling and n(n-1)/2 links. In a star everything depends on the central hub or switch, a bus dies if its backbone cable is cut, and a ring can be halted by one break.
💡 Key Conceptual Anchor:
Fault tolerance ranking: mesh highest, star depends on the central device, bus and ring are single-point-of-failure designs.
🎯 Examiner's Trap & Study Tip:
For n nodes a full mesh needs n(n-1)/2 links, so 5 nodes need 10 links - use that to spot the mesh option.
Q8 of 50
★ PPSC
★ NTS
The IEEE 802.11ac Wi-Fi standard, marketed as Wi-Fi 5, operates in which frequency band?
Correct Answer: Option C — 5 GHz
Detailed Academic Explanation:
802.11ac works only in the 5 GHz band, using wide channels and multiple streams for high throughput. The 2.4 GHz band belongs to 802.11b and 802.11g, which is why it is the tempting but wrong choice, and 60 GHz is used by 802.11ad.
💡 Key Conceptual Anchor:
Wi-Fi bands: 802.11b and g on 2.4 GHz; 802.11a, n and ac on 5 GHz (n dual-band); 802.11ax on both; 802.11ad on 60 GHz.
🎯 Examiner's Trap & Study Tip:
Higher band means higher speed but shorter range and weaker wall penetration: 5 GHz is faster, 2.4 GHz travels farther.
Q9 of 50
★ FPSC
★ PPSC
A network that links all the computer systems of one city, such as the offices of a city district government, is classified as a:
Correct Answer: Option B — MAN
Detailed Academic Explanation:
A Metropolitan Area Network spans a city and sits between a building or campus LAN and a country-wide or global WAN. The tempting LAN answer applies only to a single site, while a PAN covers a few metres around one person, such as Bluetooth links.
💡 Key Conceptual Anchor:
Coverage ladder: PAN (personal, metres) then LAN (building or campus) then MAN (city) then WAN (country and beyond).
🎯 Examiner's Trap & Study Tip:
Match the prefix to the scale: Metro means city. The Internet itself is the largest WAN.
Q10 of 50
★ PPSC
★ NTS
A rule-based gate that inspects traffic between a trusted internal network and an untrusted external network, allowing or blocking it, is called a:
Correct Answer: Option A — Firewall
Detailed Academic Explanation:
A firewall enforces an access-control policy on flows between network zones through packet filtering, stateful inspection or proxying. A modem only modulates signals for a line, a NIC is a host's network adapter, and a spam filter screens e-mail content rather than network traffic.
💡 Key Conceptual Anchor:
Firewall = policy enforcement point between zones; it can be packet-filtering, stateful or proxy-based.
🎯 Examiner's Trap & Study Tip:
Keep three words apart: spam is junk mail, phishing is the deceptive mail, the firewall is the network gate.
Q11 of 50
★ FPSC
★ PPSC
Which type of encryption uses a mathematically linked public and private key pair, as in RSA, so that data sealed with one key opens only with the other?
Correct Answer: Option A — Asymmetric (public-key) encryption
Detailed Academic Explanation:
Asymmetric encryption uses a public key for enciphering and the matching private key for deciphering, which solves key distribution and enables digital signatures. Symmetric systems such as AES rely on one shared secret, while hashing is a one-way digest that cannot be decrypted at all.
💡 Key Conceptual Anchor:
Symmetric = one shared key, fast, key-exchange problem; asymmetric = public and private key pair, slower, enables signatures and key exchange.
🎯 Examiner's Trap & Study Tip:
Public key encrypts, private key decrypts. Real systems such as TLS are hybrids: asymmetric to agree a session key, symmetric for the data.
Q12 of 50
★ NTS
★ PPSC
An e-mail that appears to come from a well-known bank and urges the recipient to click a link and enter login details on a look-alike website is an example of:
Correct Answer: Option A — Phishing
Detailed Academic Explanation:
Phishing is the fraudulent attempt to obtain credentials or payment data by impersonating a trusted party, usually by e-mail or SMS. Ransomware is different: it encrypts the victim's files and demands payment, wardriving maps wireless networks, and sniffing is passive interception of traffic.
💡 Key Conceptual Anchor:
Social engineering (phishing, smishing, vishing) versus malware (ransomware, trojan) versus passive eavesdropping (sniffing).
🎯 Examiner's Trap & Study Tip:
Any question about a fake bank or courier e-mail asking for credentials is phishing; unsolicited bulk mail in general is spam.
Q13 of 50
★ PPSC
★ FPSC
Which category of malicious software replicates and spreads across a network by itself, without attaching to a host program or waiting for a user to run anything?
Correct Answer: Option C — Worm
Detailed Academic Explanation:
A worm is self-propagating: it exploits network services to copy itself without user action, which is how outbreaks spread machine to machine. A virus needs a host file or document and user action to execute, a trojan is harmful code disguised as legitimate software, and spyware is defined by covert data collection rather than replication.
💡 Key Conceptual Anchor:
Worm = self-replicating over a network; virus = needs a host and user action; trojan = disguised as useful software; spyware = covert information theft.
🎯 Examiner's Trap & Study Tip:
The word worm implies it crawls on its own - no host file and no click. If the stem mentions a disguised free utility, answer trojan instead.
Q14 of 50
★ NTS
★ FPSC
Which one of the following Internet acronyms is correctly expanded?
Correct Answer: Option C — VoIP - Voice over Internet Protocol
Detailed Academic Explanation:
VoIP stands for Voice over Internet Protocol, the carrying of voice calls as IP packets. The others are mis-expanded: ISP is Internet Service Provider, URL is Uniform Resource Locator, and HTML is HyperText Markup Language while HTTP is the HyperText Transfer Protocol.
🎯 Examiner's Trap & Study Tip:
Sequence the web trio: a URL is the address, HTTP is the protocol used to fetch it, HTML is the markup language of the page returned.
Which protocol is used to automatically assign TCP/IP configuration information?
Correct Answer: Option B — DHCP
Detailed Academic Explanation:
DHCP is the correct answer to “Which protocol is used to automatically assign TCP/IP configuration information”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
In IT networking, which of the following device is used in physical layer?
Correct Answer: Option A — Repeater
Detailed Academic Explanation:
Repeater is the correct answer to “In IT networking, which of the following device is used in physical layer”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
Star is the correct answer to “Which Network topology needs HUB for its working”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
Latin is the correct answer to “Virus is the word of which language”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
Correct Answer: Option C — every computer is capable of playing the role of client, server or both at the same time
Detailed Academic Explanation:
every computer is capable of playing the role of client, server or both at the same time is the correct answer to “In peer-to-peer networking:”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
BUS is the correct answer to “Which of the following is a network topology”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
Fourth generation mobile technology provides enhanced capabilities allowing the transfer of both____________data, including full-motion video, high-speed internet access, and video conferencing.
Correct Answer: Option D — voice and non-voice
Detailed Academic Explanation:
Fourth generation mobile technology provides enhanced capabilities allowing the transfer of both voice and non-voice data, including full-motion video, high-speed internet access, and video conferencing.
Which of these is not a means of personal communication on the internet?
Correct Answer: Option D — Insta notes
Detailed Academic Explanation:
Insta notes is the correct answer to “Which of these is not a means of personal communication on the internet”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
What is the name of an application program that gathers user information and sends it to someone through the Internet?
Correct Answer: Option C — Spybot
Detailed Academic Explanation:
Spybot is the correct answer to “What is the name of an application program that gathers user information and sends it to someone through the Internet”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
The thing that eventually terminates a worm virus is a lack of:
Correct Answer: Option C — Memory or disk space.
Detailed Academic Explanation:
Memory or disk space. is the correct answer to “The thing that eventually terminates a worm virus is a lack of:”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
A self replicating program, similar to a virus which was taken from a 1970s science fiction novel by John Bruner entitled the Shockwave Rider is__________?
Correct Answer: Option C — Worm
Detailed Academic Explanation:
A self replicating program, similar to a virus which was taken from a 1970s science fiction novel by John Bruner entitled the Shockwave Rider is Worm .
Which device is required for the Internet connection?
Correct Answer: Option B — Modem
Detailed Academic Explanation:
Modem is the correct answer to “Which device is required for the Internet connection”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
Vint Cerf is the correct answer to “Who is the father of Internet”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
If you have a PowerPoint show you created and want to send using email to another teacher you can add the show to your email message as a (an)___________?
Correct Answer: Option A — Attachment
Detailed Academic Explanation:
If you have a PowerPoint show you created and want to send using email to another teacher you can add the show to your email message as a (an) Attachment .
In order to email a Word document from within MS Word 2016?
Correct Answer: Option B — File >> Share >> Email
Detailed Academic Explanation:
File >> Share >> Email is the correct answer to “In order to email a Word document from within MS Word 2016”. Items of this type are drawn from the Networking & Cyber Security syllabus of Pakistani competitive exams, where the fact is tested verbatim.
If you have a PowerPoint show you created and want to send using email to another teacher you can add the show to your email message as a (an)____________?
Correct Answer: Option A — Attachment
Detailed Academic Explanation:
If you have a PowerPoint show you created and want to send using email to another teacher you can add the show to your email message as a (an) Attachment .