Computer Networks MCQ Questions And Answers

Computer Networks MCQ Questions And Answers

71. What is FTP and which port does it use?

  1. File Transfer Protocol — uses port 80
  2. File Transfer Protocol — uses port 21
  3. Fast Transfer Protocol — uses port 25
  4. File Transfer Protocol — uses port 443

Answer : B
Explanation: FTP (File Transfer Protocol) is an application layer protocol used to transfer files between a client and a server over a network. It uses port 21 for control connections (commands) and port 20 for data transfer. FTP transmits data in plain text, making it insecure. SFTP (SSH File Transfer Protocol) and FTPS (FTP Secure) are the encrypted alternatives recommended for secure file transfers.

72. What is the purpose of the traceroute (tracert) command?

  1. To test if a remote host is online
  2. To display the path and measure transit delays of packets across a network
  3. To show the MAC address of a device
  4. To display the current IP configuration of a device

Answer : B
Explanation: Traceroute (called tracert on Windows) is a network diagnostic tool that displays the route packets take from source to destination and measures the delay at each hop. It works by sending packets with incrementally increasing TTL values and recording the ICMP “Time Exceeded” responses from each router along the path. It is extremely useful for identifying where network delays or failures are occurring.

73. What is a broadcast address in networking?

  1. The first IP address in a subnet used to identify the network
  2. The last IP address in a subnet used to send data to all devices in that network simultaneously
  3. The IP address of the default gateway
  4. A special address used only by routers

Answer : B
Explanation: A broadcast address is the last IP address in a subnet and is used to send data to all devices on that network simultaneously. For example, in the 192.168.1.0/24 network, the broadcast address is 192.168.1.255. When a device sends a packet to this address, every device on the subnet receives it. Broadcast addresses cannot be assigned to individual hosts.

74. What is the loopback address in IPv4 and what is it used for?

  1. 192.168.0.1 — used as the default gateway address
  2. 127.0.0.1 — used to test the TCP/IP stack on the local machine itself
  3. 255.255.255.255 — used for broadcasting
  4. 0.0.0.0 — used for unspecified addresses

Answer : B
Explanation: The loopback address 127.0.0.1 (also referred to as “localhost”) is a special IP address used to test the TCP/IP network stack on the local machine without sending any data over the physical network. The entire 127.0.0.0/8 range is reserved for loopback. If you can ping 127.0.0.1 successfully, it confirms that TCP/IP is properly installed and functioning on your device.

75. What is the difference between half-duplex and full-duplex communication?

  1. Half-duplex sends data faster than full-duplex
  2. Half-duplex allows transmission in one direction at a time; full-duplex allows simultaneous two-way transmission
  3. Full-duplex only works on wireless networks
  4. Half-duplex supports more devices than full-duplex

Answer : B
Explanation: In half-duplex communication, data can travel in both directions but only one direction at a time — like a walkie-talkie. In full-duplex, data travels in both directions simultaneously — like a telephone call. Modern Ethernet switches operate in full-duplex mode, significantly improving network efficiency. Hubs operate in half-duplex, which is why switches replaced them in modern networks.

76. What is CIDR (Classless Inter-Domain Routing)?

  1. A method that uses fixed class-based subnet masks only
  2. A method of IP address allocation that replaces class-based addressing and allows variable-length subnet masks
  3. A protocol used for encrypting IP packets
  4. A routing protocol used within a single autonomous system

Answer : B
Explanation: CIDR (Classless Inter-Domain Routing) was introduced in 1993 to replace the rigid class-based IP addressing (Class A, B, C) system. It allows network prefixes of any length (e.g., /22, /27) rather than fixed 8, 16, or 24-bit boundaries. This enables more efficient use of IP addresses and reduces the size of routing tables through route aggregation (supernetting). CIDR notation writes addresses as IP/prefix (e.g., 192.168.1.0/24).

77. Which protocol provides reliable, connection-oriented communication at the Transport layer?

  1. IP
  2. ARP
  3. UDP
  4. TCP

Answer : D
Explanation: TCP (Transmission Control Protocol) operates at the Transport Layer (Layer 4) and provides reliable, connection-oriented communication. It guarantees that all data arrives at the destination correctly and in the right order through acknowledgments, sequencing, and retransmission of lost packets. It is used by applications that require guaranteed delivery such as web browsing (HTTP/HTTPS), email (SMTP), and file transfer (FTP).

78. What is a default gateway in networking?

  1. The first device to receive a DHCP request on the network
  2. The IP address of the router that forwards traffic from a local network to other networks or the internet
  3. The DNS server used by default on the network
  4. The switch that all devices connect to within a LAN

Answer : B
Explanation: A default gateway is the IP address of the router (or Layer 3 device) that a device sends traffic to when it needs to communicate with a device on a different network or the internet. Think of it as the “exit door” of your local network. If a device does not have a default gateway configured, it can only communicate with devices on its own subnet.

79. What is SSL/TLS and which layer of the OSI model does it operate at?

  1. A routing protocol — operates at Layer 3
  2. A security protocol for encrypting data in transit — operates at the Presentation/Session layer
  3. A protocol for assigning IP addresses — operates at Layer 2
  4. A file transfer protocol — operates at Layer 7

Answer : B
Explanation: SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) are cryptographic protocols that provide encrypted communication over a network. They operate between the Transport and Application layers — primarily associated with the Presentation Layer in the OSI model. TLS is used by HTTPS, SMTP over TLS, and many other protocols. TLS 1.3 is the current recommended version, offering improved security and performance over older versions.

80. What is a proxy server and how does it differ from a VPN?

  1. A proxy server and VPN are identical in functionality
  2. A proxy server forwards requests on behalf of clients without full encryption; a VPN encrypts all traffic between the client and server
  3. A VPN only works for web browsing; a proxy works for all applications
  4. A proxy server assigns IP addresses; a VPN routes traffic between networks

Answer : B
Explanation: A proxy server acts as an intermediary between a client and destination servers, forwarding requests on the client’s behalf. It can cache content and filter traffic but does not necessarily encrypt all traffic. A VPN (Virtual Private Network) creates an encrypted tunnel for ALL network traffic from the client device, providing stronger privacy and security. VPNs protect against eavesdropping while proxies primarily focus on anonymity and content filtering.

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