Introduction to router of What is router?

Introduction to router

What is router?

Router is a layer 3 device or it is network layer device which is used for to connect different network with each other and judge the shorest path to transfer the data.

Manufacture of router:-

  1. Cisco
  2. Juniper
  3. 3com
  4. Hp
  5. D-lint...etc.

Internal component of router:-

  • Microprocessor:-

in this microprocessor we use the RISC technology it is available 70MHz up to 1.0 GHz and above. Generally Motorola companies microprocessor is use.

  • Ram:-

it is use to save running configuration available in 16, 32, 64, 128,256 MB.

  • Flash:-

this is hdd of router which is used to store os configuration of the router. Available in 16, 32, 64, 128 MB.

  • Nvram:-

it consist the startup configuration.

  • Rom:-

it is bios of router.

External component of router

  • Console:-

this is use for to access router from PC.

  • Serial port:-

use for to connect one router with another router in WAN or local place it is available in 60 pin 32 pin.

  • Ethernet:-

this is use to connect the router with switch. It is available in,
 Ethernet  10 Mbps
 Fast ethernet  100 Mbps
 Giga byte ethernet  10 Gbps

  • Auxiliary port:-

this is use to connect dial-up model.

Layer of router

  Router is divided logically by cisco in following 3 layer.

  • Access layer:-

 this is the company layer router or desktop router in this there are 800, 900, 1400, 1700, 1800, 2500 series.

  • Distribution layer:-

 this is used for ISP to distribute the network. It is included 2600, 2800, 3500, 3600, 3700, 3900, 4500, 5600 series.

  • Core layer:-

 this is backbone, mostly use for global ISP. It is included 2600, 2800, 3500, 3700, 3900, 4500, 5600 series.

How to access router in PC

For win XP and 2003 server

Start --- program --- accessories --- communication --- hyper terminal --- type name --- ok --- select com l --- ok --- restore default --- ok.

Modes of router

Router>:-user mode some command are work.

Router# :- this is the privilege mode all show commands, verification, save, copy, erase of router done from this mode.

Router (config)# :- this is configuration mode all the configuration of router done.

Editing tool

Ctrl A - move cursor to beginning of the line
Ctrl E - move cursor to end of the line
Esc B - move cursor back one word
Esc F - move cursor forward by one word
Ctrl D - or backspace - deletes a single character
Ctrl U - erse a line
Ctrl R - redisplays a line
Ctrl W - erase a word
Ctrl Z - ends the configuration mode and returns to exec mode
Tab - finishing typing a command
Ctrl P - shows last command typed
Ctrl N - shows previous command entered

Booting process of router

POST (Power On Self-Test):-

1. When any device start at that time BIOS check the configuration of that device.
2. When you start router at that time POST is used to test router hardware.
3. After that the POST load, the boot strap program locates the cisco IOS and load it into ram.
4. Locating and loading IOS into RAM the location of IOS file is specified by value of configure registry setting.
5. The bits in the setting can instruct the device to load IOS file from following location from flash memory and registry setting is 0x2102.
6. After IOS is loaded boot start up program search for startup configure file in NVRAM.
7. This file contains interface address, routing information, passwords and other configured parameter.
8. If there is no configuration file the router prompts the user to enter into setup mode to begin configuration process.
9. If a startup configuration file is found then hostname will display the router has successfully loaded IOS and configure file.

Basic configuration of router

IOS Basic Commands:-

 Router >?  Help
 Router >show?  Lists all the commands in Show
 Router >s?  Lists all the commands starting with ‘S’
 Router >  show terminal shows terminal configuration and history buffer size
 Router >  show version shows the version
 Router >  show flash shows details of ‘flash’
 Router >  enable to enter privilege exec mode
 Router #  show history show last ten commands
 Router #  terminal history size 20 to set history size to 20
 Router #  showrunning-configuration to display contents of Dynamic RAM

How to move Forward:-

Router #config t

How to move back:-

Router (config)#Ctrl+z OR exit OR end
Router #
Exit – Go back to the or exit the current mode
End or Ctrl+z – Go to the privilege mode

How to provide host name

Router#config t
Router (config)#hostname R1
R1#copy running-config startup-config OR


Banner is used to display some message when user login to the router it is display before user mode. How to provide Banner

Router#config t
Router(config)#banner motd #
Enter the text message end with the #character This is universal router#
Router (config)#exit
Router #wr

How to remove banner

Router#config t
Router (config)# no banner motd #
Router (config)#exit
Router #wr

How to provide IP address on interfaces

Fast Ethernet:-

Router#config t
Router (config)#int f0/0
Router (config-if)#ip add
Router (config-if)#no shut
Router (config)#ctrl+z
Router #wr

Serial port:-

It is use to connect one router to another router in local LAN or WAN it is use DTE and DCE

Provide IP Address on Serial port:-

Router#config t
Router (config)#int s1/0
Router (config-if)#ip add
Router (config-if)#no shut
Router (config)#ctrl+z
Router #wr

Show commands

Show commands are useful for to view the configuration information all related information above router, view the routing table. This command only works in privilege mode but, if you use “do” before the show command then it is work in configuration mode also.

Router # sh version

This command will be used to view information aboutIOS version, router model, IOS file, memory information, interface information, registry information.

Router# sh flash

This is use for to view the information about flash IOS file use available memory.

Router# sh interface

This is use for to view information about all interface connected into router serial port,fast Ethernet port.

Router# sh interface brief

This command is very helpful to view all the very brief information about all connected interface briefly.

Router# shint f0/0

This command is use to view particular interface information of fast Ethernet port

Router# sh controller s1/0

This command use to view the information about serial port like cable connected to DTE (Data Terminal Equipment) or DCE (Data Communication Equipment) Cable.

Router# sh clock time

Use to view current date

How to set date and time:-
Router# clock set 5:10:30 2 mon 22 2016

Router# sh ip protocol

This command is use for to view the all routing protocol information.

Router# sh history

This is use for previous use commands history it display max 10 commands history by default you will able to change history.
  By default history size is 10 then if you want to change history size then you required to use following commands.

Router# sh terminal

Router # terminal history size 50
You can put any value instead of 50 in above command

Router# sh running config

This command is useful for to view the configuration is work in RAM.

Router# sh startup-configuration

Display the configuration in the startup.

Router# sh users

Display the user which is connected to the router.

Router # sh dhcp server

Display the DHCP server information.

Password of Router

We are able to provide password to the router for protection. We provide Line Console, Line VTY (VirtualTeletYpe)password, enable secret password, enable password.

Line Console password:-

This password will be ask whenyou login to router from console line it will be ask before user mode.

Router#configure t
Router (configure)#line console 0
Router (configure-line)#pass ccna
Router (configure-line)#ctrl+z
Router #wr

How to remove line console password

Router#config t
Router (config)#line console 0
Router (config-line)# no pass 
Router (config-line)#ctrl+z
Router #wr

Line vty password (virtual terminal password):-

Router#config t
Router (config)#line vty 0 4
Router (config-line)# pass ccna
Router (config-line)#login
Router (config-line)#ctrl+z
Router #wr

How to remove line vty password

Router#config t
Router (config)#line vty 0 4
Router (config-line)#no pass
Router (config-line)#login
Router (config-line)#ctrl+z
Router #wr

Enable secret password:-

This is use for to provide secretly when user move from user mode to privilege mode.
Router # config t
Router (config)#enable secret ccna
Router (config)#ctrl+z
Router #wr

How to remove enable secret password

Router#config t
Router (config)#no enable secret 
Router (config)#ctrl+z
Router #wr

Enable password:-

This is also secure to user mode to privilege mode but if we use enable secret the password will not ask because it is not interrupted.
Router#config t
Router (config)#enable pass ccna
Router (config)#ctrl+z
Router #wr

How to remove enable password

Router#config t
Router (config)# no enable pass
Router (config)#ctrl+z
Router #wr

Service password encryption:-

When you fill the password some password not encrypted it is display in running configuration to encrypt it you must use the service password encryption command.
Router#config t
Router (config)# service pass-encryption

How to break Router password

When you fill the password at that time the registry value is 0x2102, if this value is set then each time when you start router it will ask password.
But if you set registry value 0x2142 then startup configuration will not ask ignore 
the password.
Step 1: Press on/ off button of router

Step 2: Press ctrl+pause break button
ROMmon (Read Only Memory monitor) mode will appear then,

Step 3: Rommon1> confreg 0x2142

Step 4: Rommon 2>i or reset

Router will be reset and Message appear “would you like to enter initial 
configuration y/n…….n”

Router#config t
Router (config)#line vty 0 4
Router (config-line)# pass ccna 
Router (config-line)#login
Router (config-line)#ctrl+z
Router #wr
Router#config t
Router (config)#enable secret ccna
Router (config)#configure-register 0x2102
Router (config)#ctrl+z
Router #wr
Router# reload

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