Network Definition: A digital telecommunications network that allows nodes to share resources
Network Components: Clients, servers, switches, routers, and firewalls working together
End Hosts/Endpoints: Devices at the edge of the network (PCs, servers, smartphones)
SWITCHES
Purpose: Connect multiple devices within the same LAN
Characteristics:
Many ports (typically 24+)
Layer 2 device (data link layer)
Provide LOCAL connectivity only
Cannot route between different networks
Examples: Cisco Catalyst 9200, Catalyst 3650
ROUTERS
Purpose: Connect different networks together
Fewer interfaces than switches
Layer 3 device (network layer)
Route traffic between LANs and across the Internet
Make forwarding decisions based on IP addresses
Examples: Cisco ISR 1000, ISR 900, ISR 4000
FIREWALLS
Purpose: Security device that monitors and controls traffic
Types:
Network Firewalls: Hardware devices between networks
Host-based Firewalls: Software on individual devices
Next-Generation Firewalls (NGFW): Advanced filtering capabilities
Examples: Cisco ASA 5500-X, Firepower 2100
CLIENTS & SERVERS
Client: Device that accesses/requests services
Server: Device that provides services
Key Point: Same device can be both (depending on situation)
Device
Port Count
Scope
Layer
Primary Function
Switch
Many (24+)
Single LAN
Layer 2
Connect hosts locally
Router
Few
Multiple Networks
Layer 3
Connect different networks
Firewall
Varies
Network boundary
Multiple
Security filtering
Switch vs Router Confusion
❌ WRONG: "Switches connect different networks"
✅ CORRECT: "Switches connect devices in the SAME network"
Client/Server Roles
❌ WRONG: "A device is always a client OR a server"
✅ CORRECT: "Devices can be BOTH depending on the transaction"
Firewall Types
❌ WRONG: "All firewalls are hardware devices"
✅ CORRECT: "Firewalls can be hardware (network) OR software (host-based)"
LAN Connectivity
❌ WRONG: "Switches can route traffic to the Internet"
✅ CORRECT: "Switches only work within a LAN; routers are needed for Internet"
What is the primary function of a switch?
To provide connectivity to hosts within the same LAN (Local Area Network). Switches have many ports (24+) and operate at Layer 2.
Can a switch provide connectivity between different LANs or to the Internet?
No. Switches only connect devices within the SAME LAN. Routers are required for inter-network connectivity.
What is the primary function of a router?
To provide connectivity BETWEEN LANs and send data over the Internet. Routers have fewer interfaces than switches and operate at Layer 3.
How many network interfaces do switches typically have compared to routers?
Switches have MANY interfaces (usually 24+), while routers have FEWER interfaces.
Define a client in networking terms.
A client is a device that ACCESSES a service made available by a server.
Define a server in networking terms.
A server is a device that PROVIDES functions or services for clients.
Can the same device act as both a client and a server?
Yes! The same device can be a client in some situations and a server in others, depending on whether it's accessing or providing a service.
What is the primary function of a firewall?
To monitor and control network traffic based on configured security rules.
What are the two types of firewalls?
Network firewalls - Hardware devices that filter traffic BETWEEN networks
Host-based firewalls - Software applications that filter traffic on individual devices
What is a Next-Generation Firewall (NGFW)?
A firewall that includes modern and advanced filtering capabilities beyond traditional firewalls (deep packet inspection, application awareness, intrusion prevention).
Where can firewalls be placed in a network?
Firewalls can be placed either "inside" the network or "outside" the network (at the perimeter).
What does LAN stand for and what does it mean?
Local Area Network - a network that connects devices in a limited geographic area (same building/campus).
Give 3 examples of Cisco switch models.
Catalyst 9200, Catalyst 3650 (know at least 2 for the exam)
Give 3 examples of Cisco router models.
ISR 1000, ISR 900, ISR 4000 (know at least 2 for the exam)
Give 2 examples of Cisco firewall models.
ASA 5500-X, Firepower 2100
What are "end hosts" or "endpoints"?
Devices at the edge of a network that either provide or consume services (PCs, servers, smartphones, printers, etc.)
In a scenario where you need to connect 30 PCs in a department, which device would you use?
A SWITCH - it has many ports (24+) designed to connect multiple end hosts in the same LAN.
In a scenario where you need to connect two separate office networks (New York and Tokyo), which device would you use?
A ROUTER - it's designed to connect different networks together and route traffic between them.
When you stream a YouTube video, what role is your device playing?
CLIENT - your device is accessing/requesting the video service from YouTube's servers.
When someone downloads a file from your phone using AirDrop, what role is your phone playing?
SERVER - your phone is providing the file (service) to another device.
Question Type: "Which device should you use for..."
30+ devices in one office → Switch
Connecting branch offices → Router
Blocking unauthorized access → Firewall
Given a transaction, identify if device is client or server:
Receiving service = Client
Providing service = Server
Can't access Internet from LAN → Check router (switches don't provide Internet connectivity)
Unauthorized access → Check firewall rules
Devices in same office can't communicate → Check switch
Last changed23 days ago