CCNA Chapter 1 - Networking Fundamentals

What is Networking?

Networking connects computers and other devices to share data and resources. It forms the foundation of communication from small homes to enterprise and internet-level connections.

OSI Model (7 Layers)

The OSI model is a conceptual framework that standardizes network communication into 7 distinct layers:

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Layer	Name	Function
7	Application	User interface and network services
6	Presentation	Data encoding, encryption
5	Session	Session control and maintenance
4	Transport	TCP/UDP, reliability, flow control
3	Network	IP addressing and routing
2	Data Link	MAC addressing and frame forwarding
1	Physical	Cabling, signals, physical media

TCP/IP Model

The TCP/IP model simplifies the OSI model into 4 layers used in real-world networking:

TCP/IP Layer	Corresponding OSI Layers
Application	7, 6, 5
Transport	4
Internet	3
Network Access	2, 1

Network Topologies

Bus: All devices share a single communication line.
Star: Devices connect to a central switch or hub.
Ring: Devices form a closed loop with data passing in one direction.
Mesh: Every device connects to every other for redundancy.

Ethernet Standards

Standard	Speed	Media
10BASE-T	10 Mbps	Cat3/Cat5
100BASE-TX	100 Mbps	Cat5
1000BASE-T	1 Gbps	Cat5e/Cat6
10GBASE-T	10 Gbps	Cat6a/Cat7

IP Addressing: IPv4 and IPv6

IPv4: 32-bit addresses written as four octets, e.g. 192.168.1.1.

Classes:

Class A: 1.0.0.0 – 126.255.255.255
Class B: 128.0.0.0 – 191.255.255.255
Class C: 192.0.0.0 – 223.255.255.255

Subnetting: Divides networks into logical segments to optimize traffic.

IPv6: 128-bit addresses, written as hexadecimal, e.g. 2001:0db8:85a3::8a2e:0370:7334.