Giáo trình CCNA - Chương 2

Router Component: RAM• RAM, also called dynamic RAM DRAM, has the following functions: – Stores routing tables – Holds ARP cache – Holds fast-switching cache – Performs packet bufferin

CCNA – Semester2

Module 1 WANs and Routers

Introduction to WANs

• These are the major

characteristics of WANs:

– They connect devices that are

separated by wide geographical

areas

– They use the services of carriers

– They use serial connections of

various types to access

bandwidth over large geographic

areas.

WANs characteristics

• A WAN operates at the physical layer and the data link layer of the OSI reference model

• It interconnects LANs that are usually separated

by large geographic areas.

• WANs provide for the exchange of data packets

and frames between routers and switches and the LANs they support

WAN Devices

WAN Standards

• WAN physical layer protocols describe how to

provide electrical, mechanical, operational, and

functional connections for WAN services

• WAN data link protocols describe how frames are carried between systems on a single data link.

WAN standards and OSI model

Physical Layer

LLC sublayer Network

Layer

WAN: Physical Layer standards

• Describes the interface

between the DTE and the DCE

Typical WAN Layer 2 Links

Circuit-switched

PPP, SLIP, HDLC

Telephone Company

Packet-switched

X.25, Frame Relay, ATM

Service Provider

WAN: Data Link Layer standards

• HDLC

í High-Level Data Link Control

í IEEE standard from SDLC

í Point-to-point and multipoint links

í Operates over sync links

• LAPB

í Link Access Procedure Balanced

í used by X.25 protocol

• LAPD

í Link Access Procedure D-channel

í ISDN D-Channel for control signal

• LAPF

í Link Access Procedure Balanced

í Used in Frame Relay for fast frame switching over high-quality digital facilities

• SLIP

í Serial Line Interface Protocol

í Designed to carry IP packets

í Being replaced by PPP

• PPP

í Point-to-Point Protocol

í Support multiple network layer

protocols (IP, IPX, DecNET)

í Operates over sync or async links

• SDLC

í Synchronous Data Link Control

Protocol

í IBM designed protocol

í Point-to-point & multipoint links

í Operates over sync links

A typical WAN setup

Point-to-point or circuit-switched connection

CO Switch

Customer Premises Equipment Demarcation

Local Loop WAN service provider toll network

Trunks and switches

S S

S S S

S S

Internetwork with router

• Consistent end-to-end addressing

• Addresses that represent network topologies

• Best path selection

• Dynamic or static routing

• Switching

Academy approach to hands-on labs

• In the academy lab,

devices that make up the

WAN cloud are simulated

by the connection

between the back-to-back

DTE-DCE cables

Routers

Introduction to routers in a WAN

• A router is a special type of

computer It has a CPU, memory,

a system bus, and various

input/output interfaces

• Routers need the Internetwork

Operating System software (IOS)

to run configuration files.

• Configuration files contain the

instructions and parameters that

control the flow of traffic in and

out of the routers.

Router Component: CPU

• The Central Processing Unit (CPU) executes

instructions in the operating system Among these functions are system initialization, routing functions, and network interface control

• The CPU is a microprocessor Large routers

may have multiple CPUs

Router Component: RAM

• RAM, also called dynamic RAM (DRAM), has the

following functions:

– Stores routing tables

– Holds ARP cache

– Holds fast-switching cache

– Performs packet buffering (shared RAM)

– Provides temporary memory for the configuration file of the router while the router is powered on

– Loses content when router is powered down or restarted

Router Component: RAM

• RAM provides run time space for executable Cisco IOS software and its subsystems

• RAM is usually logically divided into main

processor memory and shared input/output (I/O)

• RAM can be upgraded by adding additional Dual

In-Line Memory Modules (DIMMs)

Router Component: NRAM

• NVRAM has the following characteristics and

functions:

– Provides storage for the startup configuration file

– Retains content when router is powered down or restarted

• In some devices it is implemented in the same

flash device

Router Component: Flash

• Holds the operating system image (IOS)

• Allows software to be updated without removing and replacing chips on the processor

• Retains content when router is powered down or

restarted

• Can store multiple versions of IOS software

• Is a type of electronically erasable, programmable ROM (EEPROM)

• Adding or replacing the flash Single In-Line Memory Modules (SIMMs) or PCMCIA cards can upgrade the amount of flash

Router Component: ROM

• Maintains instructions for power-on self test

(POST) diagnostics

• Stores bootstrap program and basic operating system software, load Cisco IOS software from Flash ro RAM

• Some routers also have a scaled down version

of the IOS that can be used as an alternative boot source

• Requires replacing pluggable chips on the

motherboard for software upgrades

Router Component: Interfaces

• Three types of interfaces are local-area network

(LANs), wide-area network (WANs), and

Console/AUX.

• Connect router to network for frame entry and exit , or connect to terminal for configuration

• Can be on the motherboard or on a separate

module ( fixed or modular card )

Router Component: Interfaces

• LAN interfaces (Ethernet, FDDI, ATM ) and WAN

interfaces(serial, ISDN, CSUs ) have controller chips that provide the logic for connecting the system to the media

• The Console/AUX ports are serial ports used

primarily for the initial configuration of the

router.

Router Component: Power Supply

• The power supply provides the necessary power

to operate the internal components.

• Larger routers may use multiple or modular

power supplies

• In some of the smaller routers the power supply

may be external to the router

2600 External Connection

Management Ports

• Provides a text-based connection for the

configuration, monitoring and troubleshooting

of the router

• The common management interfaces are the

console and auxilliary ports These are EIA-232 asynchronous serial ports

• Computer must run a terminal emulation

program to provide a text-based session with the router

Management Ports Connections

Management Ports Connections

• The console port is preferred because it

displays router startup, debugging, and error messages by default

• The console port can also be used when the

networking services have not been started or have failed Therefore, the console port can be used for disaster and password recovery

procedures.

Connecting console interfaces

• Configure terminal

emulation software on

the PC for with the

appropriate com port

and settings

• Connect the RJ-45

connector of the

rollover cable to the

router console port

• Connect the other end

of the rollover cable to

• WANs standards and protocols

• Router internal components

• Router functions

• Router management ports

• Router LAN and WAN connection

Module 2 Introduction to Router

Objectives

• Function and operation of IOS

• Establishing session and log into router

• CLI help features

Operating Cisco IOS Software

Purpose of Cisco IOS Software

• Basic routing and switching functions

• Reliable and secure access to networked

resources

• Network scalability

Router user interface

• The Cisco IOS software uses a command-line interface (CLI) as the traditional console

Router user interface modes

• The Cisco (CLI) uses a hierarchical structure

• Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode The IOS provides a command interpreter service known as the command executive (EXEC).

User EXEC and Privileged EXEC

• The user EXEC mode

allows only a limited

number of basic

monitoring commands

This is often referred to

as a “view only” mode.

• The privileged EXEC

mode accesses all router

commands This mode

can be configured to

require a password from

the user before accessing

Check for IOS

• To see the IOS image and version that is

running, use the show version command, which also indicates other system settings.

• The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image

Command: show version

ROM: System Bootstrap, Version 11.0(10c), SOFTWARE

BOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version

11.0(10c), RELEASE SOFTWARE (fc1)

LAB_A uptime is 0 minutes

System restarted by reload

System image file is " flash:c1700-ny-mz.122-13.T8.bin ", booted via flash

cisco 2500 (68030) processor (revision N) with 6144K/2048K bytes

2 Serial network interface(s)

32K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read ONLY)

Configuration register is 0x2102

Command: show flash

System flash directory:

File Length Name/status

1 5895768 c1700-ny-mz.122-13.T8.bin

[5895832 bytes used, 2492776 available, 8388608 total] 8192K bytes of processor board System flash (Read ONLY)

Starting a Router

Router Startup Sequence

Setup Mode

• Setup is not intended as the mode for entering

complex protocol features in the router

• Setup mode is to install a minimal configuration for a router, unable to locate a configuration from another source.

• Setup mode is called when there is no

configuration file at startup or when user issue

Setup Mode

• At startup, if you see the question “ Would you like to enter the initial configuration dialog ?”, answer no

• Jump out of setup mode without saving by pressing Ctrl+C

Router LED indicators

• Cisco routers use LED indicators to provide

Keyboard help in the router CLI

• Typing a question mark ( ? ) displays a handy list

of available commands

• The " More " prompt at the bottom of the

display indicates that multiple screens are

available as output Press the Spacebar to view the next page, or Enter key to view the next line.

• The dollar sign ( $ ) indicates that the line has been scrolled to the left

Editing and History Functions

Router command history

• With the command history feature, the following

tasks may be completed:

– Set the command history buffer size

– Recall commands

– Disable the command history feature

• terminal history size or the history size {0-256} : change the number of command lines the

system records during a terminal session

(default is 10)

Summary

• Purpose and operation of IOS

• IOS naming convention

• CLI: use EXEC and privileged EXEC mode

• CLI help and editing command

• Show version

Module 3 Configuring a Router

Objectives

• Basic router configuration

• The importance of backups and documentation

Configuring a Router

CLI Command Modes

Global Configuration Modes

Password Configuration

enable secretcommand, which is encrypted, is prefered and overideenable password

Configuring an interface

Interfaces status

• Router interfaces have 2 status indications:

interface (up/down) and line protocol (up/down), the links only work if both are up.

• By default, router interfaces are shutdown and

the status is: interface is administratively down, line protocol is down

Configuring serial link

• One side must be considered a DCE and provide

a clocking signal

Router(config-if)#clock rate <link_speed(bps)>

• On Cisco router, HDLC is the default encapsulation on serial link

Router(config-if)#encapsulation <encap_type>

• By default, serial interface is of DTE device , shutdown

and have no ip address

• Configure router hostname:

Router(config)#hostname Center

Center(config)#

Flash NVRAM

RAM

Internetwork Operating System

Programs

Active Configuration File

Tables and Buffers

Backup Configuration File

Operating Systems

Router# show version Router# show flash

Router# show interfaces

Router# show processes CPU

Router# show protocols

Router# show running-config

Or Router# write term

Router# show mem

Router# show stacks

Router# show buffers

Router# show startup-config

Or Router# show config

Router Commands: Show

Examining the show Commands

• There are many show commands that you can use to examine the contents of files in the router and for

troubleshooting.

• In both privileged EXEC and user EXEC modes, the

command show ? provides a list of available show

• show clock – Shows the time set in the router

• show hosts – Displays a cached list of host names and addresses

• show users – Displays all users who are connected to the router

• show history – Displays a history of commands that have been entered

Show commands

and what IOS files are stored there

• show version– Displays information about the router and

the IOS that is running in RAM

• show ARP – Displays the ARP table of the router

• show protocol– Displays the global and interface specific

status of any configured Layer 3 protocols

• show startup-configuration – Displays the saved

configuration located in NVRAM

• show running-configuration – Displays the configuration

currently running in RAM

Back to default configuration

• Running configuration file can never be erased

but you can bring router to default configuration erasing startup-config file and restart router:

– erase startup-config

– reload

– Save configurations changes (yes/no)? no

Finishing the Configuration

network to function smoothly

• Creating standards for network consistency helps

reduce network complexity , the amount of

unplanned downtime , and exposure to events that may have an impact on network performance

Description and Banner

• An interface description should be used to notify important information such as a distant router, a circuit number, or a specific network segment.

• A login banner is a message that is displayed at login and is useful for conveying messages that affect all network users, such as notices of impending system shutdowns.

Host Name Resolution

• Host name resolution is the process that a computer

system uses to associate a host name with an IP address

• Host names, unlike DNS names, are significant only on the router on which they are configured

• Defines a static hostname-IP mapping

ip host hostname [tcp-port number] address1 [address2…address8]

Router (config)#

ip host command

ip address command Description

hostname name of host, can be a combination of character &

number tcp-port number TCP port to connect to when using host name with

EXEC connect or telnet commands, default is 23

(telnet) address1 IP address represented by hostname

address2…8 (Optional) may specify up to 8 IP addresses

ip name-server command

Router (config)#

ip name-server server-addr1 [server-addr2…server-addr6]

• Defines one or more DNS servers

ip name-server command Description

name-server name of host, can be a combination of

character & number server-addr1 IP address of primary name server

server-addr2…server-addr6

(Optional) may specify up to 6 additional IP addresses

display a cached list of HOST table

show hosts command Description

Host Host name learnt

Flag Status of this host name entry

permanent (perm) Permanent entry as entered by administrator into router configuration

temporary (temp) Host name entry learnt by DNS server (removed after 72 hours of

inactivity)

?? Not sure about this entry, need to re-validate

Age Time interval (in hours) router last referred to this entry

Type Protocol field (IP, HP-IP)

HOST Table

Loopback Interface

Router (config)#

interface loopback loopback_interface_number

• A virtual interface that is always up and allows sessions (BGP, RSRB…) to stay up even if the out- bound interface is down

• Packets routed to the loopback interface are rerouted back to the router or access server and processed locally

•Use loopback interface to simulate an active

interface

Configuration backup and documentation

• Management of device configuration includes the following tasks:

– Listing and comparing configuration files on running devices

– Storage of configuration files on network servers

– Performing software installations and upgrades

Configuration File with TFTP server