Filter
Top Products
CHAPTER
5-1
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
5
Using the Command-Line Interface
This chapter describes the Cisco IOS command-line interface (CLI) and how to use it to configure the
Cisco ASR 901 router.
Contents
• Understanding Command Modes, page 5-1
• Understanding the Help System, page 5-3
• Understanding Abbreviated Commands, page 5-4
• Understanding no and default Forms of Commands, page 5-4
• Understanding CLI Error Messages, page 5-4
• Using Command History, page 5-5
• Using Editing Features, page 5-6
• Searching and Filtering Output of show and more Commands, page 5-9
• Accessing the CLI, page 5-9
• Saving Configuration Changes, page 5-10
Understanding Command Modes
The Cisco IOS user interface is divided into different modes. The commands depend on which mode you
are currently in. Enter a question mark (?) at the system prompt to obtain a list of commands for each
command mode.
When you start a session on the router, you begin in the user mode, often called user EXEC mode. Only
a limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC
commands are one-time commands, such as show commands, which show the current configuration
status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved
when the router reboots.
To gain access to all the commands, enter privileged EXEC mode. You need to enter a password to enter
privileged EXEC mode. From this mode, you can enter any privileged EXEC command or enter global
configuration mode.