Tuesday, August 21, 2012

Cisco Router Configuration Command Line Interface (CLI) Modes

You can learn the different Router CLI configuration modes and their specifications here. This article will help you to passing your Cisco certification exams. Generally the lower end Cisco Routers uses different commands than the mid to upper range routers. The commands we are using on different Cisco Routers are almost the same, but there are always a few variations to these commands depending on the interfaces your Cisco Router has, IOS version, and the type of WAN protocols they support.

User Exec Mode:

This is the first mode you'll see on a Cisco Router is user exec mode. This is also the default mode when you are connected the Router using Telnet. You can't write or add to a configuration in this mode, but you can run quite a few show commands. This is a good mode to have users in who need to see the configuration, but shouldn't be allowed to change it.

The user exec mode prompt will look like this:

Cisco-Router>

Privilege or Enable Mode:

This mode has two names, the official one being privileged exec mode. It's more commonly referred to as enable mode, since "enable" is what you type to get into this mode. Now you got complete access privileges of Cisco device but this mode gives you more options for show and other commands, but you still can't configure anything.

Router>enable

Router#

Cisco Router Setup Mode:

Cisco Router will go to the setup mode if it is brand new or with default condition. After completing the booting process, Cisco Router will prompt in setup mode for initial configuration dialogue if there is no configuration in the memory. Already configured Cisco Router will not prompt setup mode directly. You can also enter into the Router setup mode any time by using setup command.

The Cisco Router setup mode commands are as follows:

Router # setup

System Configuration Dialog Continue with configuration dialog? [Yes/no]: Y

At any point you may enter a question mark "?" for help

Use ctrl-c to abort the configuration dialog at any prompt

Default settings are in square brackets "[ ]"

Basic management setup configures only enough connectivity for management of the Router, extended setup will ask you to configure each interface on the Router.

Would you like to enter basic management setup? [Yes/no] n

Global Configuration Mode:

To configure the Cisco Router, you must have to enter the global mode. To enter into this mode, issue the configure terminal or config t command from the privileged EXEC mode. All the configurations are done in this mode, and you can also issue a show command like in privilege exec mode by using Do command.

This mode we can call as Global mode or Global configuration mode

Router#conf t

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

Router(config)#

Interface Mode:

To configure any interface, you have to enter the interface's configuration mode. To enter into this mode, issue the interface command from the global configuration mode. You can go back to the privileged EXEC mode by pressing CTRL+Z or issue an END command. To exit from this mode, issue the EXIT command, and you'll be moved to the global configuration mode. You can also use show commands with DO command here.

Router(config)#interface serial0

Router(config-if)#

Sub Interface Configuration Mode:

To configure any logical interfaces on Cisco Router, you have to enter the sub interface's configuration mode. To enter into this, issue the interface command from the global configuration mode with sub or logical interface number.

Router(config)#interface FastEthernet 0/0.1

Router(config-subif)#

Router Configuration Mode:

To configure a Router protocol, you have to enter a specific Routing protocol command in global configuration mode. If want to execute a privileged EXEC commands such as the show command, you can execute using DO command. You can go back to the privileged EXEC mode by pressing CTRL+Z or with END command. To exit from this mode, issue the exit command, and you'll be moved to the global configuration mode.

Router(config)#router rip

Router(config-router)#exit

Router(config)#

Line Configuration Mode:

To configure authentication to access the router using the console port or remotely, you have to enter the configuration mode of the specific line(s). To enter into this, issue the line command from the global configuration mode or other configuration mode. If you wish to execute a privileged EXEC command such as the show command, you can precede it by the DO command. You can go back to the privileged EXEC mode by pressing CTRL+Z or with END command. To exit from this mode, issue the exit command, and you'll be moved to the global configuration mode.

The prompt config-line indicates that you're in line configuration mode.

Router#conf t

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

Router(config)#line console 0

Router(config-line)#password cisco

Router(config-line)#login

Router(config-line)#line vty 0 4

Router(config-line)#password cisco

Router(config-line)#login

Notice that you do not have to exit one interface mode to go to another one. Let's say that you've configured your VTY lines and now want to put an IP address on your Ethernet interface. You don't have to go out with ctrl-z and then start again - you can go straight to interface config mode from line config mode. Just make sure you see the prompt change.

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