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Cisco ASR 901 Aggregation Services Router Command Reference Guide
OL-26031-07
Chapter 1 Using Command-Line Interface
Understanding Command Modes
Understanding Command Modes
The Cisco ASR 901 series router Cisco IOS user interface is divided into many different modes. The
commands that are available to you depend on which mode you are currently in. You can obtain a list of
commands that are available for each command mode by entering a question mark
(
?
) at the system
prompt.
When you start a session on the Cisco ASR 901 series router, you begin in user mode, often called EXEC
mode. Only a limited subset of the commands are available in EXEC mode. In order to have access to
all commands, you must enter privileged EXEC mode. Normally, you must enter a password to enter
privileged EXEC mode. From privileged EXEC mode, you can enter any EXEC command or enter global
configuration mode. Most EXEC commands are one-time commands, such as
show
commands, which
show the current status of a given item, and
clear
commands, which clear counters or interfaces. The
EXEC commands are not saved across reboots of the Cisco ASR 901 series router.
The configuration modes allow you to make changes to the running configuration. If you later save the
configuration, these commands are stored across Cisco ASR 901 series router reboots. In order to get to
the various configuration modes, you must start at global configuration mode where you can enter
interface configuration mode, subinterface configuration mode, and a variety of protocol-specific modes.
ROM-monitor mode is a separate mode that is used when the Cisco ASR 901 series router cannot boot
properly. If your Cisco ASR 901 series router or access server does not find a valid system image when
it is booting, or if its configuration file is corrupted at startup, the system might enter ROM-monitor
mode.
Table 1-3
provides a summary of the main command modes.
For more information on command modes, refer to the “Using the Command Line Interface” chapter of
the
Configuration Fundamentals Configuration Guide
.
Table 1-3
Summary of Main Command Modes
Command
Mode
Access Method
Prompt
Exit Method
User EXEC
Log in.
Router>
Use the
logout
command.
Privileged
EXEC
From user EXEC mode,
enter the
enable
EXEC
command.
Router#
To exit to user EXEC mode, enter the
disable
command.
To enter global configuration mode, enter the
configure terminal
privileged EXEC command.
Global
configuration
From privileged EXEC
mode, enter the
configure terminal
privileged EXEC
command.
Router(config)#
To exit to privileged EXEC mode, enter the
exit
or
end
command or press
Ctrl-Z
.
To enter interface configuration mode, enter an
interface
configuration command.
Interface
configuration
From global
configuration mode,
enter by specifying an
interface with an
interface
command.
Router(config-if)#
To exit to global configuration mode, enter the
exit
command.
To exit to privileged EXEC mode, enter the
exit
command or press
Ctrl-Z
.
To enter subinterface configuration mode, specify a
subinterface with the
interface
command.
