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Routers

• A router is a computer• Computers have four basic components:

– a CPU, – memory, – interfaces, and – a bus

• The router is a computer that selects the best paths, and manages the switching of packets between two different networks

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Cisco Routers

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Router - internal components

• RAM/DRAM– Stores routing tables, ARP cache, fast-switching

cache, packet buffering (shared RAM), and packet hold queues.

– also provides temporary and/or running memory for the router’s configuration file while the router is powered on.

– RAM content is lost when you power down or restart.

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Router - internal components

• NVRAM – non-volatile RAM– stores a router’s backup/start-up configuration

file; – content remains when you power down or

restart

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Router - internal components

• Flash – erasable, reprogrammable ROM– holds the operating system image and microcode– allows you to update software without removing

and replacing chips on the processor – content remains when you power down or restart– multiple versions of IOS software can be stored in

Flash memory

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Router - internal components

• ROM – contains power-on diagnostics, – a bootstrap program, and – operating system software– software upgrades in ROM require replacing

pluggable chips on the CPU

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Router - internal components

• Interface– network connection through which packets

enter and exit a router– it can be on the motherboard or on a separate

interface module

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Routing

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Router Configuration

• A router is made up of configurable components.

• A router has modes –examining, –maintaining, and –changing the components.

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Router Configuration

• show commands are used for examination.• You use cdp to show entries about

neighbours.• You access other routers by using telnet.• You test network connectivity layer by layer.• Testing commands include ping, trace, telnet, and

debug

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Router Configuration

• A router can be configured from many locations: Upon initial installation, it is configured from the

console terminal. The console terminal is a computer connected to the router through the console port.

It can be connected via modem by using the auxiliary port.

After it is installed on the network, it can be configured from Virtual Terminals 0 through 4.

• Files can also be downloaded from a TFTP server on the network

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Router Modes• Whether accessed from the console or by a Telnet

session through a TTY port, the router can be placed in several modes.

• Each mode provides different functions: – User EXEC mode– Privileged EXEC mode– Set-up mode– Global configuration mode– Other configuration modes

– RXBOOT mode

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Router Modes User EXEC mode

A “look-only” mode in which the user can view some information about the router, but cannot change anything.

Privileged EXEC mode Supports the debugging and testing commands,

detailed examination of the router, manipulation of configuration files, and access to configuration modes.

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Router Modes Set-up mode

Presents an interactive prompted dialog at the console that helps the new user create a first-time basic configuration.

Global configuration mode• Implements powerful one-line commands that

perform simple configuration tasks.

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Router Modes Other configuration modes

Provide more detailed multiple-line configurations.

RXBOOT mode– A maintenance mode that can be used, among

other things, to recover lost passwords.

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Router Status Commands show version

Displays the configuration of the system hardware, the software version, the names and sources of configuration files, and the boot image.

show processes Displays information about the active processes.

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Router Status Commands

show protocols Displays the configured protocols. This command shows the status of all

configured Layer 3 protocols. show mem

Shows statistics about the router’s memory, including memory free pool statistics.

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Router Status Commands

show stacks Monitors the stack use of processes and interrupt

routines and displays the reason for the last system reboot.

show buffers Provides statistics for the buffer pools on the router.

show flash Shows information about the Flash memory device.

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Router Status Commands

show running-config Displays the active configuration file.

show startup-config Displays the backup configuration file.

show interfaces– Displays statistics for all interfaces configured

on the router.

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Cisco Discovery Protocol (CDP)

• CDP provides a single proprietary command that enables network administrators to access a summary of what the configurations look like on other directly connected routers.

• CDP runs over a data link layer connecting lower physical media and upper-network-layer protocols.

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CDP

• Because CDP operates at this level, CDP devices that support different network-layer protocols can learn about each other.

• CDP starts up automatically at boot up. CDP can then automatically discover neighbouring Cisco devices running CDP.

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CDP

• Discovered devices extend beyond those having TCP/IP.

• CDP discovers directly connected Cisco devices regardless of which Layer 3 and 4 protocol suite they run.

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CDP• CDP provides information about each CDP neighbour device.

Values include the following: Device identifiers—For example, the router’s configured host

name and domain name (if any) Address list—At least one address for SNMP, up to one address

for each protocol supported Port identifier—Such as Ethernet 0, Ethernet 1, and Serial 0 Capabilities list—If, for example, the device acts as a source

route bridge as well as a router Version—Information such as that provided by the local

command show version • Platform—The device’s hardware platform; for example, Cisco

7000

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Cisco Router Configuration

• We have seen– show and– cdp commands

• show startup-config - display the backup configuration file

• show running-config—display active configuration file.

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Cisco Router Configuration

• erase startup-config - deletes the backup configuration file in NVRAM.

• reload - reloads the router, causing it to run through the entire configuration process.

• Setup - to enter setup mode from the privileged EXEC prompt.

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Cisco Router Configuration

• configure terminal—Configures manually from the console terminal.

• copy tftp running-config—Loads configuration information from a network TFTP server.

• copy running-config startup-config— Stores the current configuration from RAM into NVRAM.

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Cisco Router Configuration

• copy running-config tftp — Stores the current configuration from RAM on a network TFTP server.

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Cisco Router Configuration

Router> enablepassword:Router# configure terminalRouter(config)# [configure mode command]• e.g. interface, subinterface, controller, line,

router etc.

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Cisco Router Configuration

• Specific configuration modes:– interface mode - for configuring interfaces– subinterface mode - for configuring multiple virtual

interfaces on a single physical interface– line mode - for configuring the operation of a

terminal line– router mode - for configuring an IP routing protocol– etc.

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Cisco Router Configuration

• Configuring router identificationRouter# config termRouter(config)# hostname LABALABA#ctrl-z : back to privileged exec modeexit : back out one level

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Cisco Router Configuration

• Message of the day bannerLABA(config)#banner motd # message #

• Interface descriptionLABA(config)#interface ethernet 0LABA(config-if)#description my LAN, BG

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Password configuration

• Console password• Virtual terminal password• Privileged exec password

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Console password

LABA(config)#line console 0LABA(config-line)#loginLABA(config-line)#password cisco

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Virtual Terminal password

LABA(config)#line vty 0 4LABA(config-line)#loginLABA(config-line)#password cisco

• Enable PasswordLABA(config)#enable password classor preferLABA(config)#enable secret class

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Configuring interfaces

LABA(config)#int s 0LABA(config-if)#clock rate 56000 • clk rate is set for DCEsLABA(config-if)#bandwidth 56• no clock rate removes clock rate• shut down/no shut down

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Configuring routing protocols

LABA(config)#router ripLABA(config-router)#network 1.0.0.0LABA(config-router)# network 2.0.0.0LABA(config-router)#ctrl-zLABA(config)#ctrl-zLABA#show ip protocolLABA#show ip route [routing table]

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Configuring routing protocols

LABA>show ip interfacesLABA#debug ip rip

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Exercise - Configuring LABA

• Hostname:Router>enapassword:Router#config termRouter(config)#hostname lab-a

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Exercise - Configuring LABA

• Enable secret password - classlab-a(config)#enable secret class

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Exercise - Configuring LABA

• All appropriate interfaces with IP addresses and subnet masks

lab-a(config)#int s 0lab-a(config-if)#ip address 201.100.11.1

255.255.255.0lab-a(config-if)#clockrate 56000lab-a(config-if)#bandwidth 56

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Exercise - Configuring LABA

lab-a(config)#int e 0lab-a(config-if)#ip address 192.5.5.1

255.255.255.0lab-a(config-if)#bandwidth 56lab-a(config)#int e 1lab-a(config-if)#ip address 205.7.5.1

255.255.255.0lab-a(config-if)#bandwidth 56

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Exercise - Configuring LABA

• Configure riplab-a(config)#router riplab-a(config)#network 205.7.5.0lab-a(config)# network 192.5.5.0lab-a(config)# network 201.100.11.0

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Exercise - Configuring LABA

• Console login password - ciscolab-a(config)#line console 0lab-a(config-line)#loginlab-a(config-line)#password cisco

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Exercise - Configuring LABA

• Vty login password - ciscolab-a(config)#line vty 0 4lab-a(config-line)#loginlab-a(config-line)#password cisco