Cisco Router Configuration Tutorial

Cisco Inter-network Operating System:

Cisco IOS Modes of Operation

The Cisco IOS software provides access to several different command modes. Each command mode provides a different group of related commands. For security purposes, 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. The following table describes some of the most commonly used modes, how to enter the modes, and the resulting prompts. The prompt helps you identify which mode you are in and, therefore, which commands are available to you.

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. 

Note:

Almost every configuration command also has a no form. In general, use the no 

form to disable a feature or function. Use the command without the keyword no

to re-enable a disabled feature or to enable a feature that is disabled by default. 

For example, IP routing is enabled by default. To disable IP routing, enter the no 

ip routing command and enter ip routing to re-enable it. 

Getting Help 

In any command mode, you can get a list of available commands by entering a 

question mark (?). 

Router>?

To obtain a list of commands that begin with a particular character sequence, 

type in those characters followed immediately by the question mark (?). 

 Router#co?

 configure connect copy 

To list keywords or arguments, enter a question mark in place of a keyword or 

argument. Include a space before the question mark. 

Router#configure ?

memory  Configure from NV memory 

network  Configure from a TFTP network host 

terminal  Configure from the terminal 

You can also abbreviate commands and keywords by entering just enough 

characters to make the command unique from other commands. For example, 

you can abbreviate the show command to sh. 

Configuration Files 

Any time you make changes to the router configuration, you must save the 

changes to memory because if you do not they will be lost if there is a system 

reload or power outage. There are two types of configuration files: the running 

(current operating) configuration and the startup configuration. 

Use the following privileged mode commands to work with configuration files. 

configure terminal – modify the running configuration manually 

from the terminal. 

• show running-config – display the running configuration. 
• show startup-config – display the startup configuration. 
• copy running-config startup-config – copy the running 
• configuration to the startup configuration. 
• copy startup-config running-config – copy the startup 
• configuration to the running configuration. 
• erase startup-config – erase the startup-configuration in NVRAM. 
• copy tftp running-config – load a configuration file stored on a 
• Trivial File Transfer Protocol (TFTP) server into the running 
• configuration. 
• copy running-config tftp – store the running configuration on a 
• TFTP server. 

IP Address Configuration 

Take the following steps to configure the IP address of an interface. 

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 interface type slot/port (for Cisco 7000 series) or interface

type port (for Cisco 2500 series) to enter the interface configuration mode. 

Example: 

 Router (config)#interface ethernet 0/1

Step 4: Enter the IP address and subnet mask of the interface using the ip 

address ipaddress subnetmask command. 

Example, 

 Router (config-if)#ip address 192.168.10.1 255.255.255.0

Step 5: Exit the configuration mode by pressing Ctrl-Z 

 Router(config-if)#[Ctrl-Z]

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

Open Shortest Path First (OSPF) 

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 ospf command and follow by the process-id. 

 Router(config)#router ospf process-id

Pick the process-id which is not being used. To determine what ids 

are being used, issue the show process command. 

 Router(config)#show process

Step 4: Add the network number, mask and area-id 

 Router(config-router)#network network-number mask area area-id

The network-number identifies the network using OSPF. The mask tells which 

bits to use from the network-number, and the area-id is used for determining 

areas in an OSPF configuration. 

Example: 

 Router(config-router)#network 192.168.10.0 255.255.255.0 area 0.0.0.0

Repeat this step for all the network numbers. 

To turn off OSPF, use the following command. 

 Router(config)#no router ospf process-id