Ccna2 M3 Configuring A Router

CCNA – Semester2

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

• 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)#

Router Commands: Show Router#show version

Router#show interfaces

Router#show flash

RAM

NVRAM

Flash

Internetwork Operating System

Router#show processes CPU Router#show protocols

Tables and Buffers

Interfaces

Active Programs Configuration File

Backup Operating Configuration Systems File

Router#show mem Router#show stacks Router#show buffers

Router#show running-config Or Router#write term

Router#show startup-config Or Router#show config

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 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 • show flash – Displays information about flash memory 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

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.

ip host command Router (config)# ip ip host host hostname hostname [tcp-port [tcp-port number] number] address1 address1 [address2…address8] [address2…address8]

• Defines a static hostname-IP mapping 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 ip name-server name-server server-addr1 server-addr1 [server-addr2…server-addr6] [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…serveraddr6

(Optional) may specify up to 6 additional IP addresses

ip domain-lookup command Router (config)# ip ip domain-lookup domain-lookup • Enables the use of DNS • Enable by default

show hosts EXEC command Router#

show show hosts hosts 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)

OK

Entry is valid

EX

Entry is expired

??

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)

Address(es)

Layer 3 address(es) associated with hostname

HOST Table

Loopback Interface Router (config)# interface interface loopback loopback loopback_interface_number loopback_interface_number

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

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

Summary • • • •

Router name, description, banner, hosts.. Configure router interface Router show commands Backup configuration files

Lab Topology F0/0

F0/0

S0/0 S0/1

Lab_E

Lab_B

S0/1

S0/0

S0/0

S0/1

S0/1

Lab_C

Lab_A

S0/0 S0/0

F0/0

F0/0

S0/1

Lab_F

Lab_D F0/0

F0/0

Port

Lab_A

Lab_B

Lab_C

Lab_D

Lab_E

Lab_F

S0/0

201.10.11.1/24

199.6.13.1/24

204.204.7.1/24

192.168.3.1/24

34.10.120.1/16

N/A

S0/1

N/A

201.10.11.2/24

199.6.13.2/24

204.204.7.2/24

192.168.3.2/24

34.10.210.5/16

F0/0

172.16.11.1/16

172.18.12.1/24

172.16.11.2/16

172.17.13.1/16

172.18.12.2/24

172.17.13.2/16

CCNA2 – Module3