L3 configuring a router

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 shut

Configuring a Router

• Basic router configuration

• The importance of backups and documentation

CLI Command Modes

Global Configuration Modes

Password Configuration

enable secret command, which is encrypted, is prefered and overide enable password

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 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)> dat toc do ?

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

Router(config-if)#encapsulation <encap_type> phuong thuc ma

hoa ? Neu khong dat tu tu dong la HDLC, chi dat tren DCE

• By default, serial interface is of DTE device, shutdown and have no ip address

• Configure router hostname:

Router(config)#hostname Center – dat ten cho rounter

Center(config)#

Flash NVRAM

RAM

Internetwork Operating System

Programs ConfigurationActive

File

Tables and Buffers

Backup Configuration

File

Operating Systems

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 commands

Show commands

• show interfaces – Displays all the statistics for all the

interfaces on the router or show interfaces serial 0/1

• show controllers serial – Displays information-specific to the interface hardware

• show clock – Shows the time set in the router

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

• 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

Configuration Standards

• A standard is a set of rules or procedures that are

either widely used or officially specified

• Configuration, security, performance, and other issues must be adequately addressed for the 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

• Defines one or more DNS servers

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

Router (config)#

ip name-server command

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

addr6

server-addr2…server-(Optional) may specify up to 6 additional IP addresses

• Enables the use of DNS

• Enable by default

ip domain-lookup Router (config)#

ip domain-lookup command

show hosts EXEC command

show hosts

Router#

inactivity)

display a cached list of HOST table

HOST Table

Loopback Interface

interface loopback loopback_interface_number

Router (config)#

• A virtual interface that is always up and allows

sessions (BGP, RSRB…) to stay up even if the bound interface is down

out-• 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

Configuration File with Hyper Terminal

• Use terminal length 0 to display all the output from commands at once

• Start Capture text

• Show running-config

• Stop Capture text

• Router name, description, banner, hosts

• Configure router interface

• Router show commands

• Backup configuration files