CCNA notes

CCNA Network Devices Overview

Definition of a Network

A computer network is a digital telecommunications network that enables nodes to share resources. The nodes in a network can be various devices performing distinct functions.

Types of Nodes

1. Router

   • Connects different networks and directs data packets between them.

2. Switch

   • Connects devices within the same LAN and processes data at the data link layer.

3. Firewall

   • Provides network security by controlling the incoming and outgoing network traffic based on predetermined security rules.

4. Server

   • Provides services or resources to clients.

5. Client

   • Accesses services provided by servers.

Characteristics of End Hosts

• End hosts are either servers or clients. The same device can act as a client in one context and a server in another.

Switches

Overview of Switches

• Common Models: Cisco Catalyst 9200 and Catalyst 3650 are popular enterprise-grade switches.

• Interface Characteristics:

  • Typically have 24 or more interfaces/ports for connecting end hosts (PCs).

  • Facilitate connectivity within a LAN but do not enable communication between different LANs over the internet, which requires routers.

Routers

Overview of Routers

• Common Models: ISR 1000, ISR 900, ISR 4000

• Characteristics:

  • Generally have fewer interfaces than switches.

  • Primarily used for forwarding data between different networks and providing internet connectivity.

Firewalls

Overview of Firewalls

• Specialized devices designed for securing a network by monitoring and controlling traffic. They can be positioned outside or inside the network and include:

  • Cisco ASA5500-X

  • Firepower 2100 Series

  • Adaptive Security Appliances (ASA)

• Characteristics:

  • Regulate traffic based on specific rules.

  • Next-generation firewalls offer advanced filtering capabilities.

Interfaces and Cables

RJ-45 and Ethernet Standards

• RJ-45: The connector used at the end of copper Ethernet cables.

• Ethernet: Refers to a collection of network protocols rather than a single protocol.

• Importance of Protocols: They ensure that devices communicate effectively over a network.

Understanding Data Measurement

• Bit: Smallest unit of data