It is just a step-by-step guide for the most basic configuration needed to make the router operational. This document is intended to instruct in the basics of Cisco router configuration and maintenance.

The Cisco IOS software provides two levels of access to commands: user and privileged. The unprivileged user mode is called user EXEC mode. The privileged mode is called privileged EXEC mode and requires a password. The commands available in user EXEC mode are a subset of the commands available in privileged EXEC mode.

USER EXEC MODE:

When you are connected to the router, you are started in user EXEC mode. The user EXEC commands are a subset of the privileged EXEC commands.

PRIVILEGED EXEC MODE:

Privileged Commands Include The Following:

• Configure – Changes the software configuration.

• Debug – Display process and hardware event messages.

• Setup – Enter configuration information at the prompts.

Enter the command disable to exit from the privileged EXEC mode and return to user EXEC mode.

CONFIGURATION MODE:

Configuration mode has a set of submodes that you use for modifying interface settings, routing protocol settings, line settings, and so forth. Use caution with configuration mode because all changes you enter take effect immediately.

To enter configuration mode, enter the command configure terminal and exit by pressing Ctrl-Z.

When you first power on a new Cisco Router, you have the option of using the “setup” utility, which allows you to create a basic initial configuration. However, in this post I will show you how to do this basic setup with the Command Line Interface (CLI).

Mastering the Cisco Router CLI is essential for more complex configuration tasks and it is the most important knowledge you should acquire if you want to become a Cisco network administrator.

THE BASIC CLI MODES THAT WE WILL BE REFERRING BELOW ARE AS FOLLOWING:

Router # – User EXEC Mode

Router# – Privileged EXEC mode

Router(config)# – Global Configuration Mode

Router(config-if)# – Interface Configuration Mode

Router(config-line)# – Line Configuration Mode

Already you have some basic knowledge of CLI and how to navigate between different configuration modes (user mode, privileged exec mode etc), so let’s get started:

STEP1: CONFIGURE ACCESS PASSWORDS:

The first step is to secure your access to the router by configuring a global secret password and also passwords for Telnet or Console as needed.

Enter into Global Configuration mode from the Privileged EXEC mode:

Router# configure terminal – Privileged EXEC mode Router(config)# – Global Configuration Mode

In Global Configuration Mode you configure parameters that affect the whole router device. Here we will configure the Enable Secret password that you will be using from now own to enter into Privileged EXEC Mode from User EXEC Mode.

Router(config)# enable secret “somestrongpassword”

From now on, when you log in from user EXEC mode you will be asked for a password.

It is suggested also to configure a password for the Telnet Lines (VTY lines) which will secure your access when connecting via Telnet over the network.

Router(config)# line vty 0 4 Router(config-line)# password “strongTelnetPass” Router(config-line)# login

STEP2: CONFIGURE A ROUTER HOSTNAME:

To differentiate your Router from other devices in the network, you should configure a Hostname for your device.

Router(config)# hostname My-Router My-Router(config)#

Notice that your Router prompt changes to the new hostname that you have just set.

STEP3: CONFIGURE IP ADDRESSES FOR ROUTER INTERFACES:

This is an essential step in order for your router to be able to forward packets in the network. The most basic parameter for a Router Interface is the IP address. From Global Configuration Mode you need to enter into Interface Configuration Mode:

My-Router(config)# interface serial 1/1 My-Router(config-if)# ip address 100.100.100.1 255.255.255.252 My-Router(config-if)# no shutdown My-Router(config-if)# exit

My-Router(config)# interface fastethernet 0/1 My-Router(config-if)# ip address 192.168.10.1 255.255.255.0 My-Router(config-if)# no shutdown My-Router(config-if)# exit

STEP4: CONFIGURE ROUTING (STATIC OR DYNAMIC):

The Router’s main purpose is to find the best route path towards a destination network and forward packets according to the best path. There are two main ways a router knows where to send packets. The administrator can assign static routes, or the router can learn routes by using a dynamic routing protocol. For simple network topologies, static routing is preferred over dynamic routing. Let’s see how to configure static routes from Global Configuration Mode.

My-Router(config)# ip route [destination network] [subnet mask] [gateway]

My-Router(config)# ip route 200.200.200.0 255.255.255.0 100.100.100.2

The command above tells the router that network 200.200.200.0/24 is reachable via gateway address 100.100.100.2.

Another popular static route that we usually configure on Internet Border routers is the default static route:

My-Router(config)# ip route 0.0.0.0 0.0.0.0 50.50.50.1

The default static route above instructs the router to send ALL packets that the router does not have a more specific route entry to gateway address 50.50.50.1 (which might be the ISP gateway address).

STEP5: SAVE YOUR CONFIGURATION:

Save your current running configuration into NVRAM. This will overwrite the startup configuration.

My-Router(config)# exit My-Router# copy running-config startup-config

You can display your current configuration to verify your settings as following:

My-Router# show running-config

ROUTING PROTOCOL CONFIGURATION: Routing Information Protocol (RIP)

Step 1: Enter privileged EXEC mode:

Router>enable password

Step 2: Enter the configure terminal command to enter global configuration mode.

Router#config terminal

Step 3: Enter the router rip command

Router(config)#router rip

Step 4: Add the network number to use RIP and repeat this step for all the numbers.

Router(config-router)#network network-number

Example: Router(config-router)#network 192.168.10.0

NOTE: To turn off RIP, use the no router rip command.

Router(config)#no router rip

ALSO USEFUL COMMANDS: SPECIFY A RIP VERSION:

By default, the software receives RIP version 1 and version 2 packets, but sends only version 1 packets. To control which RIP version an interface sends, use one of the following commands in interface configuration mode:

Command	Purpose
ip rip send version 1	Configure an interface to send only RIP version 1 packets.
ip rip send version 2	Configure an interface to send only RIP version 2 packets.
ip rip send version 1 2	Configure an interface to send only RIP version 1 and version 2 packets.

HOW TO READ ROUTER/LINK STATUS:

Status of router and links can be easily determined by power LED of router and link LED of each interface (if any). However, you may find a transceiver connected to an AUI port looks like the following:

When this transceiver is correctly connected, the “POWER” LED should light. Similarly, the “LINK” and “POLARITY” LEDs should light when you inserted the cable into the RJ45 socket on the transceiver. (Note that to get this result; the other end of the cable should be connected to some other devices as well.) If these LEDs are not light, you probably have problems with the link (cable).

CISCO ROUTER CONFIGURATION COMMANDS:

Requirement	Cisco Command
Set a console password to cisco	Router(config)#line con 0 Router(config-line)#login Router(config-line)#password cisco
Set a telnet password	Router(config)#line vty 0 4 Router(config-line)#login Router(config-line)#password cisco
Stop console timing out	Router(config)#line con 0 Router(config-line)#exec-timeout 0 0
Set the enable password to cisco	Router(config)#enable password cisco
Set the enable secret password to peter. This password overrides the enable password and is encypted within the config file	Router(config)#enable secret peter
Enable an interface	Router(config-if)#no shutdown
To disable an interface	Router(config-if)#shutdown
Set the clock rate for a router with a DCE cable to 64K	Router(config-if)clock rate 64000
Set a logical bandwidth assignment of 64K to the serial interface	Router(config-if)bandwidth 64 Note that the zeroes are not missing
To add an IP address to a interface	Router(config-if)#ip addr 10.1.1.1 255.255.255.0
To enable RIP on all 172.16.x.y interfaces	Router(config)#router rip Router(config-router)#network 172.16.0.0
Disable RIP	Router(config)#no router rip
To enable IRGP with a AS of 200, to all interfaces	Router(config)#router igrp 200 Router(config-router)#network 172.16.0.0
Disable IGRP	Router(config)#no router igrp 200
Static route the remote network is 172.16.1.0, with a mask of 255.255.255.0, the next hop is 172.16.2.1, at a cost of 5 hops	Router(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1 5
Disable CDP for the whole router	Router(config)#no cdp run
Enable CDP for he whole router	Router(config)#cdp run
Disable CDP on an interface	Router(config-if)#no cdp enable

CISCO ROUTER SHOW COMMANDS:

Requirement	Cisco Command
View version information	show version
View current configuration (DRAM)	show running-config
View startup configuration (NVRAM)	show startup-config
Show IOS file and flash space	show flash
Shows all logs that the router has in its memory	show log
View the interface status of interface e0	show interface e0
Overview all interfaces on the router	show ip interfaces brief
View type of serial cable on s0	show controllers 0 (note the space between the 's' and the '0')
Display a summary of connected cdp devices	show cdp neighbor
Display detailed information on all devices	show cdp entry *
Display current routing protocols	show ip protocols
Display IP routing table	show ip route
Display access lists, this includes the number of displayed matches	show access-lists
Check the router can see the ISDN switch	show isdn status
Check a Frame Relay PVC connections	show frame-relay pvc
show lmi traffic stats	show frame-relay lmi
Display the frame inverse ARP table	show frame-relay map

CISCO ROUTER COPY COMMANDS:

Requirement	Cisco Command
Save the current configuration from DRAM to NVRAM	copy running-config startup-config
Merge NVRAM configuration to DRAM	copy startup-config running-config
Copy DRAM configuration to a TFTP server	copy runing-config tftp
Merge TFTP configuration with current router configuration held in DRAM	copy tftp runing-config
Backup the IOS onto a TFTP server	copy flash tftp
Upgrade the router IOS from a TFTP server	copy tftp flash

CISCO ROUTER DEBUG COMMANDS:

Requirement	Cisco Command
Enable debug for RIP	debug ip rip
Enable summary IGRP debug information	debug ip igrp events
Enable detailed IGRP debug information	debug ip igrp transactions
Debug IPX RIP	debug ipx routing activity
Debug IPX SAP	debug IPX SAP
Enable debug for CHAP or PAP	debug ppp authentication
Switch all debugging off	no debug all undebug all

CISCO ROUTER BASIC OPERATIONS:

Requirement	Cisco Command
Enable	Enter privileged mode
Return to user mode from privileged	disable
Exit Router	Logout or exit or quit
Recall last command	up arrow or
Recall next command	down arrow or
Suspend or abort	and and 6 then x
Refresh screen output
Compleat Command	TAB

FOR MORE INF4:

• http://www.cisco.com/public/technotes/smbsa/en/us/internet/proc_setup_router.pdf

• http://www.cisco.com/en/US/docs/routers/access/500/520/software/configuration/guide/520scg_basic.pdf

• http://www.opennet.ru/soft/cisco-configuration.html

• http://www.net130.com/class/tech_handbook/001/Cisco%207600%20Configuration%20Guide.pdf

• http://www.scribd.com/doc/15069724/Cisco-Router-Configuration-Commands

This Article Written Author By: Premakumar Thevathasan. CCNA, CCNP, CCIP, MCSE, MCSA, MCSA - MSG, CIW Security Analyst, CompTIA Certified A+.