A Note About Syntax Checker Activities (27.1.5)
When you are learning how to modify device configurations, you might want to start in a safe, non-production 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 (27.1.6)
Refer to the online course to complete this Activity.
A network administrator must know the basic IOS command structure to be able to use the CLI for device configuration.
Basic IOS Command Structure (27.2.1)
A Cisco IOS device supports many commands. Each IOS command has a specific format, or syntax, and can only be executed in the appropriate mode. The general syntax for a command, shown in Figure 27-1, is the command followed by any appropriate keywords and arguments.
Figure 27-1 Basic Command Syntax
• Keyword — This is a specific parameter defined in the operating system (in the figure, ip protocols).
• Argument — This is not predefined; it is a value or variable defined by the user (in the figure, 192.168.10.5).
After entering each complete command, including any keywords and arguments, press the Enter key to submit the command to the command interpreter.
A command might require one or more arguments. To determine the keywords and arguments required for a command, refer to the command syntax. The syntax provides the pattern, or format, that must be used when entering a command.
As identified in Table 27-2, boldface text indicates commands and keywords that are entered as shown. Italic text indicates an argument for which the user provides the value.
For instance, the syntax for using the description command is description string. The argument is a string value provided by the user. The description command is typically used to identify the purpose of an interface. For example, entering the command, description Connects to the main headquarter office switch, describes where the other device is at the end of the connection.
The following examples demonstrate conventions used to document and use IOS commands:
• ping ip-address — The command is ping and the user-defined argument of ip-address is the IP address of the destination device. For example, ping 10.10.10.5.
• traceroute ip-address — The command is traceroute and the user-defined argument of ip-address is the IP address of the destination device. For example, traceroute 192.168.254.254.
If a command is complex with multiple arguments, you may see it represented like this:
Switch(config-if)#
switchport port-security aging
{
static
|
time
time
|
type
{
absolute | inactivity
}}
The command will typically be followed with a detailed description of the command and each argument in the Cisco IOS Command Reference.
The Cisco IOS Command Reference is the ultimate source of information for a particular IOS command.
Video – Context Sensitive Help and Command Syntax Check (27.2.3)
Refer to the online course to view this video.
Hotkeys and Shortcuts (27.2.4)
The IOS CLI provides hot keys and shortcuts that make configuring, monitoring, and troubleshooting easier.
Commands and keywords can be shortened to the minimum number of characters that identify a unique selection. For example, the configure command can be shortened to conf because configure is the only command that begins with conf. An even shorter version, con, will not work because more than one command begins with con. Keywords can also be shortened.
Table 27-3 lists keystrokes to enhance command line editing.
Table 27-3 Keystrokes Shortcuts
Note: While the Delete key typically deletes the character to the right of the prompt, the IOS command structure does not recognize the Delete key.
When a command output produces more text than can be displayed in a terminal window, the IOS will display a “–More–” prompt. Table 27-4 describes the keystrokes that can be used when this prompt is displayed.
Table 27-4 Keystrokes for Navigating the “–More–” Prompt
Table 27-5 lists commands used to exit out of an operation.
Table 27-5 Keystrokes for Exiting a Command Mode
Video – Hot Keys and Shortcuts (27.2.5)
Refer to the online course to view this video.
Packet Tracer – Navigate the IOS (27.2.6)
In this activity, you will practice skills necessary for navigating the Cisco IOS, including different user access modes, various configuration modes, and common commands used on a regular basis. You will also practice accessing the context-sensitive help by configuring the clock command.