4. INTRO TO THE CLI

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What is a CLI?

• A Command-Line Interface (CLI) is the interface you use to configure Cisco devices.
• In contrast, a Graphical User Interface (GUI) offers a visual way to interact with devices.

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How Do You Connect to a Cisco Device?

1. Console Port: To initially configure a device, connect via the Console Port.
2. Cabling: You can use a Rollover Cable, such as:
   • DB9 serial connector to RJ45
   • DB9 Serial to USB

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Accessing the CLI

• You need a Terminal Emulator (e.g., PuTTY is a popular choice) to connect via “Serial” using the default settings.

Cisco Default Settings:

• Speed (baud): 9600 bits/second
• Data bits: 8
• Stop bits: 1
• Parity: None
• Flow Control: None

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User EXEC Mode

When you first enter the CLI, you start in User EXEC Mode:

(Hostname) >	// Prompt looks like THIS //

• Limitations: User EXEC mode is limited; you can view some information but cannot make any configuration changes.
• Access Privileged EXEC Mode: Use the enable command to switch to Privileged EXEC Mode.

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Privileged EXEC Mode

In Privileged EXEC Mode, you have:

(Hostname)#	// Prompt looks like THIS //

• Access: Complete access to view the device’s configuration, restart it, and more.
• Limitations: While you can change the time and save configuration files, you cannot modify the configuration.

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Command Help

• Use a Question Mark (?) to view available commands in any mode. Combine ? with a letter or partial command to list all commands that start with those letters.

• Use the TAB key to complete partially entered commands if they exist.

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Global Configuration Mode

To enter Global Configuration Mode, issue the command within Privileged EXEC mode:

Router# configure terminal
Router(config) #		// Prompt looks like THIS //

• To return to Privileged EXEC mode, type exit.

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Enabling a Password for User EXEC Mode

To set an enable password for User EXEC mode:

Router(config)# enable password (password)

• Passwords are case-sensitive.

Encrypting Passwords

To encrypt plain-text passwords visible in configuration files:

Router(config)# service password-encryption

Notes:

• Current passwords will be encrypted.
• Future passwords will also be encrypted.
• The enable secret command is not affected by this setting.

To set an enable secret (which is always encrypted):

Router(config)# enable secret (password)

• enable secret uses Level 5 encryption.

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Configuration Files

There are two configuration files stored on the device:

1. Running-config: The current, active configuration file.
2. Startup-config: The configuration file loaded upon device restart.

To view configuration files in Privileged EXEC mode:

Router# show running-config    // For running config
Router# show startup-config    // For startup config

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Saving the Running Configuration

To save the running configuration file, you can use one of the following commands:

Router# write
Building configuration...
[OK]

Router# write memory
Building configuration...
[OK]

Router# copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]

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Encrypting Passwords Again

To encrypt passwords:

Router# conf t
Router(config)# service password-encryption

• This will encrypt all current passwords and future passwords.

• The “7” indicates the encryption type used (Cisco’s proprietary encryption), which is relatively weak.

For stronger encryption, use the enable secret command:

• The “5” indicates MD5 encryption, which is much stronger.

Once you use the enable secret command, it will override the enable password.

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Deleting Commands

To cancel or delete a command you entered, use the no keyword:

For example, to disable service password-encryption:

Router(config)# no service password-encryption

• Current passwords will not be decrypted.
• Future passwords will not be encrypted.
• The enable secret will not be affected.

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Additional Images

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