Troubleshooting guide

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Cisco PGW 2200 Softswitch Release 9.8 Operations, Maintenance, and Troubleshooting Guide
OL-0800-14
Chapter 4 Maintenance and Troubleshooting Overview
Troubleshooting Strategy Overview
Using Debug Commands
The debug commands in privileged EXEC mode can provide information about the traffic being seen
(or not seen) on an interface. This information includes error messages that network nodes generate,
protocol-specific diagnostic packets, and other useful troubleshooting data.
Caution Be careful when using debug commands. These commands are processor-intensive and can cause
serious network problems (degraded performance or loss of connectivity) if they are enabled on an
already heavily loaded router. When you finish using a debug command, remember to disable it with its
specific no debug command, or use the no debug all command to turn off all debugging.
Note Output formats vary among debug commands. Some commands generate a single line of output per
packet. Other commands generate multiple lines of output per packet. Some commands generate large
amounts of output; other commands generate only occasional output. Some commands generate lines of
text; other commands generate information in field format.
To minimize the negative impact of using debug commands, follow this procedure:
Step 1 Enter the no logging console global configuration command on your router. This command disables all
logging to the console terminal.
Step 2 Establish a Telnet session to a router port and enter the enable EXEC command.
Step 3 Enter the terminal monitor command on your router to copy debug command output and system error
messages to your current terminal display.
This procedure permits you to view debug command output remotely, without being connected through
the console port. Following this procedure minimizes the load that is created by using debug commands
because the console port no longer has to generate character-by-character processor interrupts.
If you intend to keep the output of the debug command, spool the output to a file. Cisco IOS Debug
Command Reference provides the procedure for setting up such a debug output file, and complete details
about the function and output of debug commands.
Note In many situations, third-party diagnostic tools can be more useful and less intrusive than the debug
commands. For more information, see the “Third-Party Troubleshooting Tools” section on page 4-9.
Using the Ping Command
To check host accessibility and network connectivity, use the ping command in EXEC (user) or
privileged EXEC mode.
For IP, the ping command sends ICMP Echo messages. If a station receives an ICMP Echo message, it
sends an ICMP Echo Reply message back to the source. The extended command mode of the ping
command permits you to specify the supported IP header options. This command enables the router to
perform a more extensive range of test options.
We suggests using the ping command when the network is functioning properly under normal
conditions. You can compare the information that the command returns when the network is performing
as expected with the information returned by the command when you are troubleshooting a problem.