Chương 1-Giới thiệu về định tuyến và chuyển tiếp gói pdf

Chapter 1-Introduction to Routing and Packet
Forwarding
CCNA Exploration 4.0

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Objectives
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•
•
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Identify a router as a computer with an OS and hardware
designed for the routing process.
Demonstrate the ability to configure devices and apply
addresses.
Describe the structure of a routing table.
Describe how a router determines a path and switches
packets

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Routers are Computers
• Routers have many of the same hardware and software components
that are found in other computers including:
– CPU
– RAM

– ROM
– Operating System

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Routers are Computers
Routers are at the network center
• A router connects multiple networks. This means that it has multiple

•

interfaces that each belong to a different IP network.
Each network that a router connects to typically requires a separate
interface. These interfaces are used to connect a combination of both
Local Area Networks (LANs) and Wide Area Networks (WANs).

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Routers are Computers
Routers determine the best path
• The primary responsibility of a router is to direct packets destined for
local and remote networks by:
– Determining the best path to send packets.
– Forwarding packets toward their destination.

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Routers are Computers
Routers determine the best path

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Routers are Computers
Routers determine the best path

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Routers are Computers
Routers determine the best path

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8

Router as a Computer
•

•

Describe the basic purpose of a router
– Computers that specialize in sending packets over
the data network. They are responsible for
interconnecting networks by selecting the best path
for a packet to travel and forwarding packets to
their destination
Routers are the network center
– Routers generally have 2 connections:
• WAN connection (Connection to ISP)
• LAN connection
• PSTN connection
•…
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Evolution of Routers

• Multiprotocol devices providing pure data delivery with
•
•
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minimal access control and QoS.

Intelligent Network Services, this allowed us to provide
security capabilities like integrated firewall and encryption.
Integrated voice and data capabilities, allowing routers to
provide voice gateway features for IP telephony.
Today the router is an integrated platform for providing
advanced services in security, content delivery, and voice.
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Cisco Router Series

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Router Components
• Router components and their functions”
 CPU - Executes operating system instructions
 Random access memory (RAM) - Contains the running copy
of configuration file. Stores routing table. RAM contents lost
when power is off
 Read-only memory (ROM) - Holds diagnostic software used
when router is powered up. Stores the router’s bootstrap
program.
 Non-volatile RAM (NVRAM) - Stores startup configuration.
This may include IP addresses (Routing protocol, Hostname
of router)

 Flash memory - Contains the operating system (Cisco IOS)
 Interfaces - There exist multiple physical interfaces that are
used to connect network. Examples of interface types:
• Ethernet / fast Ethernet interfaces
• Serial interfaces
• Management interfaces

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Router Components(refer to 1.1.2.1)

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Router Components

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Cisco router 1841’s Architecture - Front Panel

LED

Color

Status

SYS PWR

Green

Router has successfully booted up and the software is functional.
Slow, steady blinking when system is booting or in the ROM
monitor.

SYS ACT

Green

Blinking when packets are transmitted or received on any WAN
or LAN interface, or when monitoring system activity.

CF

Blinking
green

Flash memory is busy. Do not remove the CompactFlash
memory card when this light is on.

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Cisco router 1841’s Architecture - Back Panel

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Router Components
•

Router components

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Cisco IOS Software Architecture for 1800 Series

•

Identified IOS Software includes: Feature and Version

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Router Boot-up Process
Bootup Process
•

There are four major phases to the bootup process:
– 1. Performing the POST
– 2. Loading the bootstrap program
– 3. Locating and loading the Cisco IOS software
– 4. Locating and loading the startup configuration file or entering setup
mode

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Router Boot-up Process

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Router Boot-up Process

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Verify the router boot-up process
•

The show version command is used to view
information about the router during the bootup
process. Information includes:
 Platform model number
 Image name & IOS version
 Bootstrap version stored in ROM
 Image file name & where it was loaded from
 Number & type of interfaces
 Amount of NVRAM
 Amount of flash
 Configuration register

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Verify the router boot-up process
• The show version command can be used to help verify and
troubleshoot some of the basic hardware and software components of
the router.

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Router Interfaces
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•
•
•

Router Interface is a physical connector that enables a
router to send or receive packets
Each interface connects to a separate network
Consist of socket or jack found on the outside of a router
Types of router interfaces:
Fixed: Fastethernet
Modular:
• Serial
• DSL
• ISDN
• Fastethernet

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Router Interfaces
• Two major groups of Router Interfaces
– LAN Interfaces:
 Are used to connect router to
LAN network
 Has a layer 2 MAC address
 Can be assigned a Layer 3 IP

address
 Usually consist of an RJ-45 jack

• WAN Interfaces
 Are used to connect routers to external networks that
interconnect LANs.
 Depending on the WAN technology, a layer 2
address may be used.
 Uses a layer 3 IP address
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