ccna exp2 - chapter01 - smith.n studio

8/10/2019 Ccna Exp2 - Chapter01 - Smith.N Studio

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Hc vin mng Bach Khoa - Website: www.bkacad.com 2

Objectives

Identify a router as a computer with an OS and hardwaredesigned for the routing process.

Demonstrate the ability to configure devices and applyaddresses.

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 componentsthat are found in other computers including:

CPU

RAM

ROM

Operating System




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Routers are at the network center

A router connects multiple networks. This means that it has multipleinterfaces that each belong to a different IP network.

Each network that a router connects to typically requires a separateinterface. These interfaces are used to connect a combination of both

Local Area Networks (LANs) and Wide Area Networks (WANs).




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Routers determine the best path

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

Determining the best path to send packets.

Forwarding packets toward their destination.




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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





Evolution of Routers

Multiprotocol devices providing pure data delivery withminimal 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 toprovide voice gateway features for IP telephony. Today the router is an integrated platform for providing

advanced services in security, content delivery, and voice.





Cisco Router SeriesSmith Nguyen Studio.Smith Nguyen Studio.




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 lostwhen power is off

Read-only memory (ROM) - Holds diagnostic software usedwhen router is powered up. Stores the routers bootstrap

program. Non-volatile RAM (NVRAM) - Stores startup configuration.

This may include IP addresses (Routing protocol, Hostnameof 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 ComponentsSmith Nguyen Studio.Smith Nguyen Studio.


S ith N St diS ith N St di



Cisco router 1841s 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.






Cisco router 1841s Architecture - Back PanelSmith Nguyen Studio.Smith Nguyen Studio.





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






Router Boot-up ProcessSmith Nguyen Studio.Smith Nguyen Studio.





Verify the router boot-up process

The show version command is used to viewinformation about the router during the bootupprocess. 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






The show version command can be used to help verify and

troubleshoot some of the basic hardware and software components ofthe router.

Verify the router boot-up processSmith Nguyen Studio.Smith Nguyen Studio.





Router Interfaces

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 IPaddress

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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Routers and the Network Layer

The main purpose of a router is to connect multiple networks and

forward packets destined either for its own networks or other networks. A router is considered a Layer 3 device because its primary forwarding

decision is based on the information in the Layer 3 IP packet,

specifically the destination IP address. This process is known as

routing.




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Implementing Basic Addressing Schemes

At a minimum, the documentation should include a topology diagram

that indicates the physical connectivity and an addressing table thatlists all of the following information:

Device names.

Interfaces used in the design.

IP addresses and subnet masks.

Default gateway addresses for end devices, such as PCs.





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Basic Router Configurationg yg y




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Basic Router Configurationg yg y




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Basic Router Configuration

Verifying Basic Router Configuration

Issue the show running-configcommand Save the basic router configuration by Issuing the copy

running-config startup-configcommand

Additional commands that will enable you to further verify

router configuration are: Show running-config - Displays configuration currently in

RAM

Show startup-config - Displays configuration file NVRAM

Show IP route - Displays routing table

Show interfaces - Displays all interface configurations

Show IP int brief - Displays abbreviated interface

configuration information

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Introducing the Routing Table

The following analogies may help clarify the concept of

connected, static, and dynamic routes: Directly Connected Routes.

Static Routes.

Dynamic Routes.




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Adding a Connected Network to the Routing Table

Once the interface is "up and have an ip address, the network

of that interface is added to the routing table as a directlyconnected network.




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Static Routing

Static routes in the routing table

Includes: network address and subnet mask and IP address of nexthop router or exit interface.

Denoted with the code S in the routing table.

Routing tables must contain directly connected networks used to

connect remote networks before static or dynamic routing can be

used. When to use static routes

When network only consists of a few routers.

Network is connected to internet only through one ISP.

Hub & spoke topology is used on a large network.



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Dynamic Routing

Dynamic routing protocols are used by routers to share information

about the reachability and status of remote networks. Dynamic routingprotocols perform several activities, including:

Network discovery.

Updating and maintaining routing tables.




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Dynamic Routing

Dynamic routing features:

Automatic Network Discovery.

Maintaining Routing Tables.

IP Routing Protocols RIP (Routing Information Protocol) .

IGRP (Interior Gateway Routing Protocol). EIGRP (Enhanced Interior Gateway Routing Protocol).

OSPF (Open Shortest Path First).

IS-IS (Intermediate System-to-Intermediate System).

BGP (Border Gateway Protocol).


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Routing Table Principles


3 principles regarding routing tables: Every router makes its decisions alone, based on the

information it has in its routing table.

One routers information in the routing table may not be the

same as another routers routing table.

Routing information about a path to a network does not provideinformation on how to return to the original network.



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P k t Fi ld d F Fi ldSmith Nguyen Studio.Smith Nguyen Studio.


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Packet Fields and Frame Fields

Internet Protocol (IP) packet format contains fields that provide

information about the packet and the sending and receiving hosts Fields that are importance for CCNA students:

Destination IP address.

Source IP address.

Version & TTL.

IP header length.

Precedence & type of service.

Packet length.


P k t Fi ld d F Fi ldSmith Nguyen Studio.Smith Nguyen Studio.


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Packet Fields and Frame Fields

MAC Layer Frame Format

MAC Frames are also divided into fields. They include: Preamble

Start of frame delimiter

Destination MAC address

Source MAC address Type/length

Data and pad

Frame check sequence



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Path DeterminationSmith Nguyen Studio.Smith Nguyen Studio.


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Path Determination

Path determination enables a router to evaluate paths to a destination

& to establish the preferred way to handle the packet. One of 3 things happens when a router searches a routing table to finda route to destination

Next hop determined.

Exit interface determined.

No route determined.


Switching FunctionSmith Nguyen Studio.Smith Nguyen Studio.


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Switching Function

Switching Function of Router is the process used by a router to switch

a packet from an incoming interface to an outgoing interface on thesame router.

A packet received by a router will do the following:

Strips off layer 2 headers.

Examines destination IP address located in Layer 3 header to

find best route to destination. Re-encapsulates layer 3 packet into layer 2 frame.

Forwards frame out exit interface.


Switching Function(refer to 1 4 5)Smith Nguyen Studio.Smith Nguyen Studio.


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Switching Function(refer to 1.4.5)

Step 1: PC1 has a packet to be sent to PC2



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Switching Function

Step 1: PC1 has a packet to be sent to PC2




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Switching Function

Step 2: Router R1 receives the Ethernet frame




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Switching Function




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Switching Function





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Switching Function





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Switching Function

Step 3: Packet arrives at router R2




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Switching Function





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Switching Function





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Switching Function

Step 4: The packet arrives at R3




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Switching Function





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Switching Function





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Switching Function



SummarySmith Nguyen Studio.Smith Nguyen Studio.


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Summary

Routers are computers that specialize in sending data over a

network. Routers are composed of: Hardware i.e. CPU, Memory, System bus, Interfaces Software used to direct the routing process

IOS

Configuration file Routers need to be configured. Basic configuration consists of: Router name Router banner Password(s) Interface configurations i.e. IP address and subnet mask

Routing tables contain the following information Directly connected networks Remotely connected networks Network addresses and subnet masks IP address of next hop address



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