100 Network Fundamentals: Key Concepts and Definitions

1) What is a link?

A link refers to the connection between two devices, including the cable type and protocol that enable communication.

2) What are the layers of the OSI reference model?

There are seven OSI layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

3) What is a backbone network?

A backbone network is a centralized infrastructure that routes traffic between different sub‑networks and manages bandwidth and channels.

4) What is a LAN?

LAN stands for Local Area Network, which connects computers and other devices within a small physical area.

5) What is a node?

A node is a point where a connection occurs; it can be a computer or device that forms part of a network, requiring at least two nodes to establish a link.

6) What is a router?

A router connects two or more network segments, storing routing information such as paths and hop counts to determine optimal data routes, and operates at the OSI Network layer.

7) What is a point‑to‑point link?

It is a direct connection between two computers on a network, requiring only a cable and NICs without additional networking equipment.

8) What is anonymous FTP?

Anonymous FTP allows users to access public files on a server without identifying themselves, logging in as an anonymous guest.

9) What is a subnet mask?

A subnet mask works with an IP address to separate the network portion from the host portion; like an IP address, it consists of 32 bits.

10) What is the maximum length allowed for a UTP cable segment?

A single UTP cable segment may be up to 90‑100 meters long; repeaters or switches can extend this limit.

11) What is data encapsulation?

Data encapsulation is the process of breaking information into smaller manageable units before transmission, adding source/destination addresses and checksums to headers.

12) Describe network topology.

Network topology refers to the physical layout of computers, cables, and devices in a network and how they interconnect.

13) What is a VPN?

A VPN (Virtual Private Network) creates a secure tunnel over a public network such as the Internet.

14) Briefly describe NAT.

NAT (Network Address Translation) allows multiple computers on a private network to share a single public Internet connection.

15) What is the function of the Network layer in the OSI model?

The Network layer handles routing, packet switching, and congestion control; routers operate at this layer.

16) How does network topology affect decisions when building a network?

Topology determines the media required for interconnecting devices and influences the choice of cables, connectors, and terminals.

17) What is RIP?

RIP (Routing Information Protocol) is used by routers to exchange routing information and determine network distance in hops.

18) What are common ways to protect a computer network?

Install reliable, up‑to‑date antivirus on all machines, configure firewalls correctly, and enforce user authentication.

19) What is a NIC?

A NIC (Network Interface Card) is a hardware component that provides a unique MAC address for a computer to connect to a network.

20) What is a WAN?

WAN (Wide Area Network) interconnects geographically dispersed computers and devices across regions or countries.

21) Why is the OSI Physical layer important?

The Physical layer converts data bits to electrical signals (and vice versa) and defines device and cable specifications.

22) How many layers are there under TCP/IP?

TCP/IP has four layers: Network, Internet, Transport, and Application.

23) What is a proxy server and how does it protect a network?

A proxy server hides internal IP addresses from external users, making the internal network harder to locate and target.

24) What is the function of the OSI Session layer?

The Session layer establishes, manages, and terminates communication sessions between two devices.

25) Why is implementing fault‑tolerant systems important?

Fault‑tolerant systems ensure continuous data availability by eliminating single points of failure, though they cannot protect against all issues such as accidental deletion.

26) What does 10Base‑T mean?

"10" denotes a 10 Mbps data rate, "Base" indicates baseband signaling, and "T" refers to twisted‑pair cabling.

27) What is a private IP address?

Private IP addresses are assigned for internal networks and are not routable on the public Internet, allowing reuse across multiple isolated networks.

28) What is NOS?

NOS (Network Operating System) is software that provides network connectivity for computers and devices.

29) What is DoS?

DoS (Denial‑of‑Service) attacks aim to prevent legitimate users from accessing network services by overwhelming the target.

30) What is OSI and its role in computer networking?

OSI (Open Systems Interconnection) is a 7‑layer reference model that defines how network devices communicate and interact.

31) Why are cables shielded and twisted‑pair?

Shielding and twisting reduce crosstalk and electromagnetic interference that can corrupt transmitted data.

32) What are the advantages of address sharing (NAT)?

Address sharing provides inherent security because external hosts see only the public IP of the NAT device, not internal private addresses.

33) What is a MAC address?

A MAC (Media Access Control) address uniquely identifies a device on a network and consists of six bytes.

34) Which TCP/IP layers correspond to the OSI Application layer?

The TCP/IP Application layer maps to the OSI Session, Presentation, and Application layers.

35) How do you identify the class of a given IP address?

Examine the first octet: Class A starts with 0, Class B with 10, and Class C with 110.

36) What is the primary purpose of OSPF?

OSPF (Open Shortest Path First) is a link‑state routing protocol that selects optimal paths using routing tables.

37) What is a firewall?

A firewall protects internal networks from external attacks, blocking unauthorized access and malicious traffic.

38) Describe star topology.

Star topology connects all nodes to a central hub, making it simple to set up and maintain.

39) What is a gateway?

A gateway connects two or more network segments, often running translation software to enable communication between different systems.

40) What are the disadvantages of star topology?

If the central hub or switch fails, the entire network becomes inoperable.

41) What is SLIP?

SLIP (Serial Line Internet Protocol) is an early Unix protocol used for remote access.

42) Give examples of private network addresses.

10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are common private address ranges.

43) What is tracert?

Tracert is a Windows utility that traces the route packets take to a destination, showing hop counts.

44) What are the functions of a network administrator?

Network administrators install, configure, and maintain networks, handling troubleshooting and security.

45) Describe a drawback of peer‑to‑peer networks.

When a workstation shares resources, its performance may degrade.

46) What is a hybrid network?

A hybrid network combines client‑server and peer‑to‑peer architectures.

47) What is DHCP?

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices on a network.

48) What is the main job of ARP?

ARP (Address Resolution Protocol) maps known IP addresses to MAC addresses.

49) What is TCP/IP?

TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of protocols for data exchange across heterogeneous networks.

50) How can a router be used to manage a network?

Routers provide consoles for configuring security, traffic logging, and access restrictions for devices.

51) Which protocol can be used to transfer files between UNIX and Windows servers?

FTP (File Transfer Protocol) is platform‑independent and suitable for such transfers.

52) What is the purpose of a default gateway?

A default gateway provides a path from a local network to external networks, typically using the router’s external interface address.

53) What makes a good password?

A strong password mixes letters, numbers, and case, avoiding easily guessable information like dates or names.

54) What is the correct termination resistance for UTP cable?

Unshielded twisted‑pair cables should be terminated at 100 Ω.

55) What is netstat?

Netstat is a command‑line utility that displays current TCP/IP connections and related statistics.

56) How many network IDs are available in a Class C network?

A Class C network has 21 bits for network ID, yielding 2,097,152 possible networks, each supporting up to 254 hosts.

57) What happens when a cable exceeds its specified length?

Signal loss occurs, degrading data transmission and reception.

58) What common software issues can cause network problems?

Client‑server mismatches, application conflicts, misconfigurations, protocol mismatches, security flaws, and policy issues.

59) What is ICMP?

ICMP (Internet Control Message Protocol) provides messaging and error handling for the TCP/IP stack.

60) What is Ping?

Ping is a utility that checks connectivity between network devices using IP addresses or hostnames.

61) What is P2P?

P2P (Peer‑to‑Peer) networks consist of equal workstations that communicate directly without a central server.

62) What is DNS?

DNS (Domain Name System) resolves hostnames to IP addresses for TCP/IP communication.

63) What are the advantages of fiber over other media?

Fiber is less susceptible to electrical interference, supports higher bandwidth, and experiences minimal signal degradation over long distances.

64) What is the difference between a hub and a switch?

A hub acts as a multi‑port repeater and becomes a bottleneck as devices increase, whereas a switch intelligently forwards traffic, improving performance.

65) Which network protocols does Windows RRAS support?

RRAS supports NetBEUI, TCP/IP, and IPX.

66) What are the maximum networks and hosts for Class A, B, and C?

Class A: 126 networks, 16,777,214 hosts; Class B: 16,384 networks, 65,534 hosts; Class C: 2,097,152 networks, 254 hosts.

67) What is the standard color order for a straight‑through cable?

Orange/white, orange, green/white, blue, blue/white, green, brown/white, brown.

68) Which protocols sit below the TCP/IP Application layer?

FTP, TFTP, Telnet, and SMTP.

69) Can two computers share files without a hub or router?

Yes, by using a crossover cable that directly connects the two NICs.

70) What is ipconfig?

Ipconfig displays a computer’s IP configuration, including physical (MAC) and IP addresses.

71) What is the difference between straight‑through and crossover cables?

Straight‑through cables connect devices to hubs, switches, or routers; crossover cables connect similar devices directly (e.g., PC‑to‑PC).

72) What is client/server architecture?

In client/server networks, one or more servers provide centralized resources (e.g., printers, files) while clients request those resources.

73) Describe a network.

A network is the interconnection of computers and peripheral devices for data communication, using wired or wireless links.

74) Does moving a NIC to another PC move its MAC address?

Yes, the MAC address is hard‑wired to the NIC hardware, not the PC.

75) Explain clustering support.

Clustering allows multiple servers to work together so that if one fails, another continues processing.

76) Where should antivirus be installed in a network with two servers and twenty workstations?

Antivirus should be installed on all servers and workstations to ensure comprehensive protection.

77) Describe Ethernet.

Ethernet is a widely used LAN technology defined by IEEE standards, originating in the early 1970s.

78) What is a drawback of ring topology?

A single workstation failure can bring down the entire network, and reconfiguration often requires temporary shutdown.

79) What is the difference between CSMA/CD and CSMA/CA?

CSMA/CD (Collision Detection) retransmits after a collision; CSMA/CA (Collision Avoidance) broadcasts intent before transmitting.

80) What is SMTP?

SMTP (Simple Mail Transfer Protocol) handles email transmission within the TCP/IP stack.

81) What is multicast routing?

Multicast routing sends messages to a selected group of users rather than broadcasting to all nodes.

82) Why is encryption important on a network?

Encryption transforms data into unreadable code, ensuring that intercepted information remains unintelligible without the correct key.

83) How are IP addresses formatted and displayed?

IP addresses use dotted‑decimal notation, e.g., 192.168.101.2.

84) Explain the importance of authentication.

Authentication verifies user credentials (typically username and password) before granting network access, preventing unauthorized entry.

85) What does tunnel mode mean?

In tunnel mode, IPSec creates a virtual tunnel that secures all traffic between two gateways, without encrypting the end hosts themselves.

86) What technologies are used to establish WAN links?

Analog connections (plain telephone lines), digital connections (digital subscriber lines), and switched connections (multiple link groups) are common WAN technologies.

87) What is an advantage of mesh topology?

Mesh topology provides redundancy; if one link fails, alternative paths keep the network operational.

88) What common hardware issues arise when troubleshooting networks?

Hardware failures such as hard‑drive crashes, damaged NICs, or improper hardware configurations can cause network problems.

89) How can signal attenuation be mitigated?

Using repeaters or hubs to regenerate the signal and ensuring proper cable termination can address attenuation.

90) How does DHCP assist network management?

DHCP automatically assigns IP addresses from a pool, eliminating the need to manually configure each client.

91) What is a network profile?

A profile defines configuration settings for a user, such as group membership and permissions.

92) What is Sneakernet?

Sneakernet is the practice of physically transporting data on removable media like disks or tapes.

93) What role does IEEE play in computer networking?

IEEE develops and maintains standards for networking equipment, interfaces, cabling, and connectors.

94) Which protocols operate under the TCP/IP Internet layer?

ICMP, IGMP, IP, and ARP are managed at the Internet layer.

95) What are permissions in a network context?

Permissions are authorizations that define which actions a user may perform on network resources.

96) What is a basic requirement for creating a VLAN?

A VLAN requires a switch capable of defining separate broadcast domains for security and traffic segmentation.

97) What is IPv6?

IPv6 (Internet Protocol version 6) expands the address space beyond IPv4, addressing the exhaustion of IPv4 addresses.

98) What is the RSA algorithm?

RSA (Rivest‑Shamir‑Adleman) is a widely used public‑key encryption algorithm.

99) What is mesh topology?

Mesh topology connects every device directly to every other device, requiring at least two connections per device.

100) What is the maximum segment length for a 100Base‑FX network?

A 100Base‑FX segment may be up to 412 meters; the overall network can extend up to 5 kilometers.