How to : Basic Router Configuration

Initial Router Configurations: This post shows how to configure the router initially from router boot process to optimizing router for best user experience to securing routers console and telnet ports. I am using GNS3 and router 2691 image in gns3.

Initial Router Boot Process : Router boot Process consist of

1> POST : Power On Self Test

2> Booting IOS (operationg system of cisco devices) from routers flash memory.

3> Initial Configuration Setup : I basically prefer not to set up router from initial config

When you chose no to initial config dialog router will enter into user mode which is designated as

Router> This mode is known as user mode, you can do ? for the commands you can enter in this mode. you can only use very general show commands from this mode.

Router>?

Exec commands:

access-enable Create a temporary Access-List entry

access-profile Apply user-profile to interface

clear Reset functions

connect Open a terminal connection

disable Turn off privileged commands

disconnect Disconnect an existing network connection

enable Turn on privileged commands

exit Exit from the EXEC

help Description of the interactive help system

lock Lock the terminal

login Log in as a particular user

logout Exit from the EXEC

modemui Start a modem-like user interface

mrinfo Request neighbor and version information from a multicast

router

mstat Show statistics after multiple multicast traceroutes

mtrace Trace reverse multicast path from destination to source

name-connection Name an existing network connection

pad Open a X.29 PAD connection

ping Send echo messages

ppp Start IETF Point-to-Point Protocol (PPP)

resume Resume an active network connection

rlogin Open an rlogin connection

show Show running system information

slip Start Serial-line IP (SLIP)

ssh Open a secure shell client connection

systat Display information about terminal lines

tclquit Quit Tool Command Language shell

telnet Open a telnet connection

terminal Set terminal line parameters

tn3270 Open a tn3270 connection

traceroute Trace route to destination

tunnel Open a tunnel connection

udptn Open an udptn connection

where List active connections

x28 Become an X.28 PAD

x3 Set X.3 parameters on PAD

To Enter into privilege mode do

Router>en

Router# In this mode you can do some show commands, copy commands to save your running-configuration to your routers startup configuration

To enter to the main configuration mode do

Router#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# (This is the main mode for configuring basically everything in the router)

So lets start configuring the router

How to change the hostname of router

Router(config)#hostname testrouter

testrouter(config)#

here above you can see the change in hostname from default hostname Router to testrouter

How to configure log on banner on router

testrouter(config)#banner motd *

Enter TEXT message. End with the character '*'.

Personal Router Unauthorized access Restricted

*

Above motd means message of the day and this banner is displayed at first log on. You have to enter the same Character at the start and end of each motd in this case it is *.

Below you can see how the banner is displayed

testrouter con0 is now available

Press RETURN to get started.

*Mar 1 00:24:00.555: %SYS-5-CONFIG_I: Configured from console by console
Personal Router Unauthorized access Restricted

How to Secure the console login of router : ( When you connect your router to P.C with console cable, this console password is required)

testrouter(config)#line console 0

testrouter(config-line)#password cisco

testrouter(config-line)#login (The opposite of login i.e no login will not ask for password when loggin through console of the router , which can be very risky)

How to secure telnet login of the router : This will secure the login when telneting from the remote P.C

testrouter(config)#line vty 0 ?

<1-935> Last Line number



The above command shows that this router supports 936 vty ports (virtual tele terminal i.e 936 connections )

testrouter(config)#line vty 0

testrouter(config-line)#line vty 0 4

testrouter(config-line)#login

% Login disabled on line 66, until 'password' is set

% Login disabled on line 67, until 'password' is set

% Login disabled on line 68, until 'password' is set

% Login disabled on line 69, until 'password' is set

% Login disabled on line 70, until 'password' is set

testrouter(config-line)#password test

The commands allows the telnet login for vty 0 4 and requires password test to enter to the router through telnet.

How to secure privelege/enable mode on router : This configuration will ask for the password when entering from the user mode to privilege mode

testrouter(config)#enable secret test

testrouter(config)#exit

testrouter#exit

Below shows how this router asks for the password

testrouter con0 is now available

Press RETURN to get started.

*Mar 1 00:37:34.707: %SYS-5-CONFIG_I: Configured from console by console

Personal Router Unauthorized access Restricted

User Access Verification

Password:

testrouter>en

Password:

testrouter#

How to optimize router for best user experience:

Below command should be entered both for line console and for line vty, I will be showing in console , you can do the same in line vty

testrouter(config)#line co

testrouter(config)#line console 0

testrouter(config-line)#log

testrouter(config-line)#logg

testrouter(config-line)#logging sy

testrouter(config-line)#logging synchronous

loggin synchronous will keep the status messages from interrupting what you are typing

testrouter(config-line)#exec-timeout 20 0 : exec timeout will give the timeout interval i.e here if no command is typed for 20 minutes the router will throw the user to user mode

Thank You,

In my next post of cisco basics I'll be configuring interfaces. Hope this will be informative for you

How to Configure Interface on Routers :

There may be various kinds of interfaces on the router like fastethernet, serial etc, but for all the interface, configuration are basically similar. I am going to show you here the commands for configuring the most popular interfaces i.e fastethernet and serial

testrouter#show ip interface brief (This command will show you all the interface, configured ip address, interface status, protocol status etc)

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 unassigned YES unset administratively down down

FastEthernet0/1 unassigned YES unset administratively down down

If you want more detailed description then you can do

testrouter#show interfaces ( This will show you detailed view of the interfaces like MTU size, Encapsulation on the interface, Erros etc which will be discussed later on other topics.)

you can also do

testrouter#show interfaces fastEthernet 0/0

for detailed configuration of specific interfaces.

To configure interface goto the interface in your routers

testrouter#config t

testrouter(config)#interface fastEthernet 0/0

testrouter(config-if)#ip address 192.168.1.20 255.255.255.0

testrouter(config-if)#no shutdown

*Mar 1 00:07:17.667: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up

*Mar 1 00:07:18.667: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

testrouter(config-if)#do show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 192.168.1.20 YES manual up up

FastEthernet0/1 unassigned YES unset administratively down down

As you can see from the above that now FastEthernet0/0 is configured with ip address 192.168.1.20 and its status and protocol are both up. Any time you see status up but protocol down then it means the interface is administratively down and you have to issue no shutdown commands on the interface. If status is down then you have to check your physical connection as Status deals with physical layer. By the way , you can use show commands from any mode, but you have to use it with do.

Now that our initial router configuration is over we can now switch to some major topic like routing now, so I will be posting on routing. Remember this is only router basic configuration. If you want switch configuration the please refer the link below

Cisco Switch Configurations

Thanks

ciscohowtos