Using The Debug Command; Filtering Output Using Output Modifiers - Cisco VGD-1T3 Software Configuration Manual

Using the Command-Line Interface in Cisco IOS Software
Configuration commands may also have a default form, which returns the command settings to their
default values. For commands that are disabled by default, using the default form has the same effect as
using the no form of the command. For commands that are enabled by default and have default settings,
the default form enables the command and returns the settings to their default values.
The no and default forms of commands are described in the command pages of Cisco IOS software
command references.

Using the debug Command

A debug command produces extensive output that helps you troubleshoot problems in your network.
These commands are available for many features and functions within Cisco IOS software. Some debug
commands are debug all, debug aaa accounting, and debug mpls packets. To use debug commands
during a Telnet session with a device, you must first enter the terminal monitor command. To turn off
debugging completely, you must enter the undebug all command.
For more information about debug commands, see the Cisco IOS Debug Command Reference at
http://www.cisco.com/en/US/docs/ios/debug/command/reference/db_book.html.
Debugging is a high priority and high CPU utilization process that can render your device unusable. Use
Caution
debug commands only to troubleshoot specific problems. The best times to run debugging are during
periods of low network traffic and when few users are interacting with the network. Debugging during
these periods decreases the likelihood that the debug command processing overhead will affect network
performance or user access or response times.

Filtering Output Using Output Modifiers

Many Cisco IOS commands produce lengthy output that may use several screens to display. Using output
modifiers, you can filter this output to show only the information that you want to see.
Three output modifiers are available and are described as follows:
•
•
•
To use one of these output modifiers, type the command followed by the pipe symbol (|), the modifier,
and the regular expression that you want to search for or filter. A regular expression is a case-sensitive
alphanumeric pattern. It can be a single character or number, a phrase, or a more complex string.
The following example illustrates how to filter output of the show interface command to display only
lines that include the expression "protocol."
Router# show interface | include protocol
FastEthernet0/0 is up, line protocol is up
Serial4/0 is up, line protocol is up
Serial4/1 is up, line protocol is up
Serial4/2 is administratively down, line protocol is down
Serial4/3 is administratively down, line protocol is down
begin regular expression—Displays the first line in which a match of the regular expression is found
and all lines that follow.
include regular expression—Displays all lines in which a match of the regular expression is found.
exclude regular expression—Displays all lines except those in which a match of the regular
expression is found.
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Using the CLI
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