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Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-10
Chapter 2 Using Cisco IOS XE Software
Using the no and default Forms of Commands
Using the no and default Forms of Commands
Almost every configuration command has a
no
form. In general, use the
no
form to disable a function.
Use the command without the
no
keyword to re-enable a disabled function or to enable a function that
is disabled by default. For example, IP routing is enabled by default. To disable IP routing, use the
no ip
routing
command; to re-enable IP routing, use the
ip routing
command. The Cisco IOS software
command reference
publications
provide the complete syntax for the configuration commands and
describe what the
no
form of a command does.
Many CLI commands also have a
default
form. By issuing the command
default
command-name
, you
can configure the command to its default setting. The Cisco IOS software command reference
publications describe the function of the
default
form of the command when the
default
form performs
a different function than the plain and
no
forms of the command. To see what default commands are
available on your system, enter
default ?
in the appropriate command mode.
Router(config-if)#
ip address ?
A.B.C.D IP address
negotiated IP Address negotiated over PPP
Router(config-if)#
ip address
Enter the command that you want to configure for
the interface. This example uses the
ip address
command.
Enter
?
to display what you must enter next on the
command line. In this example, you must enter an IP
address or the
negotiated
keyword.
A carriage return (<cr>) is not displayed; therefore,
you must enter additional keywords or arguments to
complete the command.
Router(config-if)#
ip address 172.16.0.1 ?
A.B.C.D IP subnet mask
Router(config-if)#
ip address 172.16.0.1
Enter the keyword or argument that you want to use.
This example uses the 172.16.0.1 IP address.
Enter
?
to display what you must enter next on the
command line. In this example, you must enter an IP
subnet mask.
A <cr> is not displayed; therefore, you must enter
additional keywords or arguments to complete the
command.
Router(config-if)#
ip address 172.16.0.1 255.255.255.0 ?
secondary Make this IP address a secondary
address
<cr>
Router(config-if)#
ip address 172.16.0.1 255.255.255.0
Enter the IP subnet mask. This example uses the
255.255.255.0 IP subnet mask.
Enter
?
to display what you must enter next on the
command line. In this example, you can enter the
secondary
keyword, or you can press
Enter
.
A <cr> is displayed; you can press
Enter
to
complete the command, or you can enter another
keyword.
Router(config-if)#
ip address 172.16.0.1 255.255.255.0
Router(config-if)#
In this example,
Enter
is pressed to complete the
command.
Table 2-5
Finding Command Options (continued)
Command
Comment