Computer Networks Interview Questions and Answers

The networking questions freshers should know, each answered in a sentence or two.

1. Q1. How many layers does the OSI model have?

   • A. 7
   • B. 4
   • C. 6
   • D. 5
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   Answer: A. 7
   Physical, Data Link, Network, Transport, Session, Presentation, Application.

2. Q2. Which protocol is connection-oriented and reliable?

   • A. TCP
   • B. IP
   • C. ICMP
   • D. UDP
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   Answer: A. TCP
   TCP uses handshakes, acknowledgements and retransmission.

3. Q3. Which protocol is used for video calls and live streaming where speed matters more than reliability?

   • A. UDP
   • B. SMTP
   • C. FTP
   • D. TCP
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   Answer: A. UDP
   UDP has no handshakes or retransmission, so it's faster.

4. Q4. What does DNS do?

   • A. Encrypts web traffic
   • B. Assigns IP addresses automatically
   • C. Translates domain names into IP addresses
   • D. Sends email
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   Answer: C. Translates domain names into IP addresses
   skillpark.org → an IP address the browser can connect to.

5. Q5. The default port for HTTPS is:

   • A. 80
   • B. 21
   • C. 443
   • D. 25
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   Answer: C. 443
   HTTP uses 80, FTP 21, SMTP 25.

6. Q6. What does DHCP do?

   • A. Automatically assigns IP addresses to devices
   • B. Resolves domain names
   • C. Encrypts data
   • D. Routes email
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   Answer: A. Automatically assigns IP addresses to devices
   Your phone gets an IP from the Wi-Fi router via DHCP.

7. Q7. What happens in TCP's three-way handshake?

   • A. SYN, FIN, RST
   • B. GET, POST, PUT
   • C. SYN, SYN-ACK, ACK
   • D. HELLO, DATA, BYE
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   Answer: C. SYN, SYN-ACK, ACK
   It sets up a connection before data flows.

8. Q8. An IPv4 address has how many bits?

   • A. 128
   • B. 32
   • C. 16
   • D. 64
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   Answer: B. 32
   IPv6 addresses have 128 bits.

9. Q9. Which device works at the Network layer and forwards packets between networks?

   • A. Router
   • B. Switch (layer 2)
   • C. Repeater
   • D. Hub
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   Answer: A. Router
   Switches forward frames inside a network using MAC addresses.

10. Q10. Which HTTP method is meant for retrieving data without side effects?

    • A. GET
    • B. DELETE
    • C. POST
    • D. PATCH
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    Answer: A. GET
    GET should be safe and idempotent.

11. Q11. What does HTTP status code 404 mean?

    • A. Server Error
    • B. OK
    • C. Unauthorized
    • D. Not Found
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    Answer: D. Not Found
    200 OK, 401 Unauthorized, 403 Forbidden, 500 Internal Server Error.

12. Q12. What does HTTPS add on top of HTTP?

    • A. Encryption and server authentication using TLS
    • B. Faster speed only
    • C. Compression only
    • D. A different port number only
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    Answer: A. Encryption and server authentication using TLS
    TLS certificates prove the site's identity and encrypt traffic.

13. Q13. A MAC address identifies:

    • A. A user account
    • B. A website
    • C. A network interface's hardware
    • D. A program
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    Answer: C. A network interface's hardware
    48 bits, usually written as six hex pairs.

14. Q14. Which layer of the OSI model handles end-to-end delivery and ports?

    • A. Transport
    • B. Network
    • C. Data Link
    • D. Session
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    Answer: A. Transport
    TCP and UDP live at the Transport layer.

15. Q15. What is the purpose of a subnet mask?

    • A. To speed up DNS
    • B. To hide your IP address
    • C. To encrypt packets
    • D. To separate the network part of an IP address from the host part
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    Answer: D. To separate the network part of an IP address from the host part
    e.g. 255.255.255.0 means the first 24 bits are the network.