21. Which layer of the OSI model is responsible for logical addressing?
- a) Network Layer
- b) Data Link Layer
- c) Transport Layer
- d) Physical Layer
Answer: A - The Network Layer (Layer 3) handles logical addressing (IP addresses) and routing.
22. What is the subnet mask for a Class C IP address?
- a) 255.255.255.0
- b) 255.255.0.0
- c) 255.0.0.0
- d) 255.255.255.255
Answer: A - Class C addresses use 255.255.255.0 as the default subnet mask (first 3 octets for network ID).
23. Which protocol is used by ping command?
- a) ICMP
- b) TCP
- c) UDP
- d) ARP
Answer: A - Ping uses ICMP (Internet Control Message Protocol) Echo Request/Reply messages.
24. What is the purpose of a default gateway?
- a) To route traffic to other networks
- b) To assign IP addresses
- c) To connect wireless devices
- d) To filter malicious traffic
Answer: A - The default gateway is the router that forwards traffic to destinations outside the local network.
25. Which port does SSH use by default?
- a) 22
- b) 23
- c) 80
- d) 443
Answer: A - SSH (Secure Shell) uses port 22 for encrypted remote access.
26. What is the main difference between TCP and UDP?
- a) TCP is connection-oriented, UDP is connectionless
- b) TCP is faster, UDP is slower
- c) TCP works only on LAN, UDP works on WAN
- d) TCP uses IP, UDP doesn't
Answer: A - TCP establishes connections with handshaking and guarantees delivery, while UDP sends datagrams without verification.
27. Which device operates at Layer 1 of the OSI model?
- a) Hub
- b) Switch
- c) Router
- d) Firewall
Answer: A - Hubs are physical layer devices that simply repeat signals to all ports.
28. What is the range of private IP addresses in Class A?
- a) 10.0.0.0 to 10.255.255.255
- b) 172.16.0.0 to 172.31.255.255
- c) 192.168.0.0 to 192.168.255.255
- d) 169.254.0.0 to 169.254.255.255
Answer: A - Class A private range is 10.0.0.0/8 (RFC 1918).
29. Which protocol resolves MAC addresses from IP addresses?
- a) ARP
- b) RARP
- c) DNS
- d) DHCP
Answer: A - ARP (Address Resolution Protocol) maps IP addresses to MAC addresses.
30. What does CSMA/CD stand for?
- a) Carrier Sense Multiple Access with Collision Detection
- b) Collision Sense Media Access with Carrier Detection
- c) Centralized Switching Multiple Access
- d) Controlled Segment Media Access
Answer: A - CSMA/CD is used in Ethernet networks to detect and handle collisions.
31. Which wireless encryption standard is most secure?
- a) WPA3
- b) WPA2
- c) WPA
- d) WEP
Answer: A - WPA3 (2018) is the current most secure standard, replacing WPA2.
32. What is the purpose of a subnet mask?
- a) To distinguish network and host portions of an IP address
- b) To encrypt network traffic
- c) To assign dynamic IP addresses
- d) To connect to a VPN
Answer: A - Subnet masks define which part of an IP address is the network ID and which is the host ID.
33. Which protocol is used for retrieving emails from a server?
- a) POP3
- b) SMTP
- c) IMAP
- d) Both A and C
Answer: D - Both POP3 (Post Office Protocol) and IMAP (Internet Message Access Protocol) are used for retrieving emails.
34. What is the maximum cable length for Ethernet (10BASE-T)?
- a) 100 meters
- b) 185 meters
- c) 500 meters
- d) 1 kilometer
Answer: A - Standard Ethernet (10BASE-T) has a maximum segment length of 100m over twisted-pair cable.
35. Which network device regenerates signals at the bit level?
- a) Repeater
- b) Hub
- c) Switch
- d) Router
Answer: A - Repeaters operate at Layer 1 to regenerate weak signals without interpreting data.
36. What does TTL stand for in networking?
- a) Time To Live
- b) Time To Load
- c) Transmission Time Limit
- d) Total Traffic Limit
Answer: A - TTL is a counter in packets that prevents infinite looping in networks.
37. Which protocol is used for network management?
- a) SNMP
- b) SMTP
- c) FTP
- d) HTTP
Answer: A - SNMP (Simple Network Management Protocol) monitors and manages network devices.
38. What is the purpose of a MAC address?
- a) To uniquely identify a network interface
- b) To route packets between networks
- c) To encrypt network traffic
- d) To assign IP addresses
Answer: A - MAC (Media Access Control) addresses are hardware identifiers for NICs (48-bit).
39. Which topology requires terminators?
- a) Bus
- b) Star
- c) Ring
- d) Mesh
Answer: A - Bus topology requires terminators at both ends to prevent signal reflection.
40. What is the primary function of a proxy server?
- a) To act as an intermediary for client requests
- b) To assign IP addresses
- c) To encrypt all network traffic
- d) To connect wireless devices
Answer: A - Proxy servers forward client requests while providing caching, filtering, or anonymity.