Understanding Routers: Functions, Components, and Setup

Posted on Jan 28, 2025 in Computers

Chapter 1: Routers

1. Routers Connect Networks

A router connects one network with another network.

2. Router Functions

Routers are also used to:

  • Ensure availability
  • Provide integrated data services, video, and voice networks, wired or wireless
  • Reduce the impact of worms, viruses, and other attacks on the network

3. Routers are Computers

Routers have many of the same hardware and software components found on other computers, including:

  • CPU
  • RAM
  • ROM
  • Operating System

4. Routers Connect Multiple Networks

A router connects multiple networks.

5. Primary Responsibility of a Router

The primary responsibility of a router is to direct packets destined for local and remote networks by:

  • Determining the best route to send packets
  • Sending packets to their destination

6. Point-to-Point Protocol (PPP)

PPP stands for Point-to-Point Protocol.

7. Asynchronous Transfer Mode (ATM)

ATM stands for Asynchronous Transfer Mode.

8. Routing Protocols and Static Routing

Routers use routing protocols and static routing to dynamically learn about remote networks and build their routing tables.

9. Router Components

  • CPU, RAM, and ROM

CPU

The CPU executes operating system instructions such as system startup, routing, and switching functions.

RAM

RAM stores instructions and data that the CPU needs to execute. RAM is used to store these components. RAM is a volatile memory and loses its contents when the router shuts down or restarts.

ROM

ROM is a form of permanent storage. ROM does not lose its contents when the router shuts down or restarts.

10. Flash Memory

Flash memory is used as permanent storage for the operating system.

11. NVRAM

NVRAM (Nonvolatile RAM) does not lose its information when power is removed.

12. Startup Process

The process of starting a router involves:

  1. Running POST
  2. Loading the bootstrap program
  3. Locating and loading Cisco IOS software
  4. Locating and loading the startup configuration file or entering Setup Mode

13. POST

POST is used to test the router’s hardware.

14. Bootstrap Program

The bootstrap program locates the Cisco IOS in RAM.

15. Show Version Command

The show version command displays information about the version of Cisco IOS software currently running on the router.

16. Main Purpose of a Router

The main purpose of a router is to connect multiple networks and send packets destined either to their own networks or other networks.

17. Basic Router Configuration Tasks

When you configure a router, you perform certain basic tasks, such as:

  • Assigning a name to the router
  • Setting passwords
  • Configuring interfaces
  • Configuring a message
  • Saving changes to a router
  • Checking the basic configuration and operation of the router

18. Routing Table

A routing table is a data file in RAM that is used to store route information on remote networks that are directly connected.

19. Dynamic Routing Protocols

Dynamic routing protocols perform a variety of activities, including:

  • Network discovery
  • Updating and maintaining routing tables

20. Principles of Routing Tables

  1. Each router makes its decision independently, according to information from its own routing table.
  2. The fact that a router has some information in its routing table does not mean that other routers have the same information.
  3. Routing information on a route from one network to another does not provide routing information on the reverse or return path.

21. Main Objective of Routing Protocols

The main objective of a routing protocol is to determine the best paths for each route.