Upon completion of this chapter, you will be able to answer the following questions:
- How do you navigate to the different Cisco IOS modes?
- How do you navigate the Cisco IOS to configure network devices?
- How do you use show commands to monitor device operations?
Key Terms
This chapter uses the following key terms. You can find the definitions in the Glossary.
Introduction (18.0.1)
Imagine you are cooking many different kinds of food on a grill, and the food comes in many shapes and sizes. You have one large spatula. You can turn the food, but the spatula is clumsy and imprecise. What tool would be better? Tongs.
Configuring devices using the GUI is like trying to flip different kinds of food with a spatula. Using the Cisco IOS command-line interface (CLI) is like using tongs. You have much more control and precision when configuring devices when you‛re using the CLI.
Navigate the IOS (18.1)
The Cisco IOS CLI is a text-based program that enables you to enter and execute Cisco IOS commands to configure, monitor, and maintain Cisco devices. The Cisco CLI can be used with either in-band or out-of-band management tasks.
The Cisco IOS Command-Line Interface (18.1.1)
CLI commands are used to alter the configuration of devices and to display the current status of processes on routers and switches. For experienced users, the CLI offers many time-saving features for creating both simple and complex configurations. Almost all Cisco networking devices use a similar CLI. When the router has completed the power-up sequence and the Router> prompt appears, you can use the CLI to enter Cisco IOS commands, as shown in Example 18-1.
Example 18-1 Enter Configuration Mode After Router Power-Up
Router con0 is now available
Press RETURN to get started!
Router>
enable
Router#
configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#
hostname R1
R1(config)#
interface gigabitethernet 0/0/0
R1(config-if)#
Technicians familiar with the IOS commands and operation of the CLI find it easy to monitor and configure a variety of different networking devices because the same basic commands are used for configuring a switch or a router. The CLI has an extensive help system that assists you in setting up and monitoring devices.
Primary Command Modes (18.1.2)
In the previous section, you learned that all network devices require an OS and that they can be configured using the CLI or a GUI. Using the CLI may provide you, as network administrator, with more precise control and flexibility than using the GUI. This section discusses using the CLI to navigate the Cisco IOS.
As a security feature, the Cisco IOS software separates management access into the following two command modes:
- User EXEC Mode—This mode has limited capabilities but is useful for basic operations. It allows only a limited number of basic monitoring commands but does not allow the execution of any commands that might change the configuration of the device. The user EXEC mode is identified by the CLI prompt that ends with the > symbol.
- Privileged EXEC Mode—To execute configuration commands, you, as network administrator, must access privileged EXEC mode. Higher configuration modes, like global configuration mode, can be reached only from privileged EXEC mode. The privileged EXEC mode can be identified by the prompt ending with the # symbol.
Table 18-1 summarizes the two modes and displays the default CLI prompts of a Cisco switch and router.
Table 18-1 Primary Command Modes
| Command Mode | Description | Default Device Prompt |
| User EXEC Mode | Mode allows access to only a limited number of basic monitoring commands. It is often referred to as “view-only” mode. | Switch> Router> |
| Privileged EXEC Mode | Mode allows access to all commands and features. You can use any monitoring commands and execute configuration and management commands. | Switch# Router# |
Video—IOS CLI Primary Command Modes (18.1.3)
Refer to the online course to view this video.
Video—Navigate Between IOS Modes (18.1.4)
Refer to the online course to view this video.
A Note About Syntax Checker Activities (18.1.5)
When you are learning how to modify device configurations, you might want to start in a safe, nonproduction environment before trying it on real equipment. NetAcad gives you different simulation tools to help build your configuration and troubleshooting skills. Because these are simulation tools, they typically do not have all the functionality of real equipment. One such tool is the Syntax Checker. In each Syntax Checker, you are given a set of instructions to enter a specific set of commands. You cannot progress in Syntax Checker unless the exact and full command is entered as specified. More advanced simulation tools, such as Packet Tracer, let you enter abbreviated commands, much as you would do on real equipment.
Syntax Checker—Navigate Between IOS Modes (18.1.6)
Refer to the online course to complete this activity.