PlacementPrepHow many layers does the OSI model have?
Solution
Physical, Data Link, Network, Transport, Session, Presentation, Application.
Answer: (D) 7
Technical · CSE / IT
Computer Networks MCQs for placement tests
20 technical questions of moderate difficulty, as asked in campus placement and company tests. Each has a short explanation.
At which OSI layer do routers operate?
Solution
Routers forward packets using IP addresses at the network layer.
Answer: (D) Network layer
At which OSI layer do switches mainly operate?
Solution
Switches forward frames using MAC addresses.
Answer: (C) Data link layer
Which protocol provides reliable, connection-oriented delivery?
Solution
TCP uses acknowledgements and retransmission; UDP does not.
Answer: (A) TCP
What is the default port number for HTTPS?
Solution
HTTP uses 80; HTTPS uses 443.
Answer: (B) 443
Which protocol translates domain names into IP addresses?
Solution
The Domain Name System resolves names like example.com to IP addresses.
Answer: (B) DNS
Which protocol automatically assigns IP addresses to devices?
Solution
DHCP gives hosts an IP address, subnet mask and gateway.
Answer: (C) DHCP
ARP is used to find:
Solution
Address Resolution Protocol maps IP addresses to MAC addresses on a local network.
Answer: (A) The MAC address for a given IP address
How many bits are in an IPv4 address?
Solution
IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses.
Answer: (B) 32
How many usable host addresses does a /24 IPv4 subnet have?
Solution
28 = 256 addresses, minus the network and broadcast addresses = 254.
Answer: (C) 254
Which of these is a private IPv4 address?
Solution
Private ranges are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.
Answer: (D) 192.168.1.10
Which protocol is used to send email between mail servers?
Solution
SMTP sends mail; POP3 and IMAP are used to retrieve it.
Answer: (A) SMTP
Which topology connects every device to a central hub or switch?
Solution
In a star topology, all nodes connect to a central device.
Answer: (A) Star
What does the 'ping' command use?
Solution
ping sends ICMP echo requests and waits for echo replies.
Answer: (B) ICMP echo messages
The TCP three-way handshake uses which sequence?
Solution
The client sends SYN, the server replies SYN-ACK, and the client sends ACK.
Answer: (B) SYN, SYN-ACK, ACK
Which device connects networks that use different protocols?
Solution
A gateway translates between different network protocols.
Answer: (A) Gateway
Which of these is a connectionless protocol suitable for live video?
Solution
UDP has low overhead and no retransmission delays, suiting real-time media.
Answer: (B) UDP
What is the full form of MAC in MAC address?
Solution
A MAC address identifies a network interface at the data link layer.
Answer: (C) Media Access Control
What does a subnet mask of 255.255.255.0 correspond to?
Solution
Three octets of 1s = 24 network bits.
Answer: (B) /24
Which layer of the OSI model handles encryption and data formatting?
Solution
The presentation layer handles translation, encryption and compression.
Answer: (A) Presentation layer
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