Cisco CCNA Preparation · lesson 1 of 36 · 25 min
What Is a Network?
A computer network is two or more devices connected together to share resources and communicate. Networks range from two laptops sharing a printer to the global internet connecting billions of devices.
The CCNA 200-301 exam expects you to identify network components, describe their roles, and explain how different physical and logical topologies affect network design and troubleshooting.
Network Components
Network Types
Physical Topologies
Enterprise three-tier hierarchy
Access layer — connects end devices (PCs, phones, APs) to the network.Distribution layer — aggregates access layer switches; applies routing, QoS, and policy.Core layer — high-speed backbone connecting distribution layers; minimal processing.
Logical vs Physical Topology
The physical topology describes how devices are physically cabled. The logical topology describes how data actually flows. A network can be physically wired as a star (all cables run to a central switch) but logically operate as a bus (all devices share the same broadcast domain).
Flashcard Drill
Router Layer 3 device that forwards packets between different networks using IP addresses. Switch Layer 2 device that forwards frames within a LAN using MAC addresses — one collision domain per port. Access Point Bridges wireless clients to the wired LAN — operates at Layer 2. LAN Local Area Network — high-speed, privately owned network within a building or campus. WAN Wide Area Network — connects geographically separated sites; lower speed, higher latency. Star topology All devices connect to a central switch — easy fault isolation; central device is single point of failure. Mesh topology Every device connects to every other — maximum redundancy; expensive; used in WANs. Three-tier hierarchy Access → Distribution → Core — scalable enterprise network design. Hub Layer 1 device that repeats signals to all ports — shared collision domain; obsolete. Physical vs logical topology Physical = how cables are run. Logical = how data actually flows.
Scenario Practice
Choosing the Right Device
A hub — it connects all devices to a shared medium. A switch — each port is its own collision domain, giving each device dedicated bandwidth. A router — it connects different networks. A modem — it provides internet access. 1 A switch creates a separate collision domain per port, eliminating collisions and giving each device its own dedicated bandwidth. A hub shares bandwidth across all ports. A router connects different networks, not workstations within the same LAN.
Knowledge Check
Network Components — 10 Questions
Which device operates at Layer 3 and forwards packets between different networks?
- Switch
- Hub
- Router
- Access Point
Answer: Router
Routers operate at Layer 3 and use IP addresses to forward packets between networks.
A switch creates how many collision domains?
- One for the entire switch
- One per VLAN
- One per port
- None
Answer: One per port
Each switch port is its own collision domain — this is why switches replaced hubs.
A hub creates a separate collision domain for each port.
- True
- False
Answer: False
A hub has ONE collision domain shared across all ports. Switches create one per port.
The network type that spans a city or metropolitan area is called a _____.
Answer: MAN
MAN (Metropolitan Area Network) connects multiple LANs across a city.
In the three-tier enterprise hierarchy, which layer connects end devices like PCs and phones?
- Core
- Distribution
- Access
- Aggregation
Answer: Access
The access layer connects end devices to the network.
Which topology provides the highest redundancy by connecting every device to every other device?
- Star
- Bus
- Ring
- Mesh
Answer: Mesh
Full mesh topology connects every device to every other — maximum redundancy but expensive.
What is the function of an Access Point (AP)?
- Routes packets between networks
- Bridges wireless clients to the wired LAN
- Filters traffic based on rules
- Provides DHCP addresses
Answer: Bridges wireless clients to the wired LAN
An AP operates at Layer 2 and bridges wireless (802.11) clients to the wired Ethernet LAN.
A WAN typically has higher speed and lower latency than a LAN.
- True
- False
Answer: False
WANs typically have lower speed and higher latency than LANs — they span greater distances.
The physical topology where all devices connect to a central switch is called:
- Bus
- Ring
- Mesh
- Star
- Answer: Star
Star topology has all devices connecting to a central device (switch or hub).
The three layers of the enterprise network hierarchy from bottom to top are: Access, Distribution, and _____.
Answer: Core
The three-tier hierarchy is Access → Distribution → Core.
Back to Cisco CCNA Preparation
Next lesson: Network topology architectures: two-tier, three-tier, spine-leaf, WAN, SOHO