Redirecting Debug And Error Message Output; Using The Show Platform Command; Using The Show Debug Command; Troubleshooting Packet Loss - Cisco Catalyst 9400 System Management Configuration Manual

Troubleshooting the Software Configuration

Redirecting Debug and Error Message Output

By default, the network server sends the output from debug commands and system error messages to the
console. If you use this default, you can use a virtual terminal connection to monitor debug output instead of
connecting to the console port .
Possible destinations include the console, virtual terminals, internal buffer, and UNIX hosts running a syslog
server. The syslog format is compatible with 4.3 Berkeley Standard Distribution (BSD) UNIX and its
derivatives.
Note
Be aware that the debugging destination you use affects system overhead. When you log messages to the
console, very high overhead occurs. When you log messages to a virtual terminal, less overhead occurs.
Logging messages to a syslog server produces even less, and logging to an internal buffer produces the least
overhead of any method.
For more information about system message logging, see Configuring System Message Logging.

Using the show platform Command

The output from the show platform hardware fed active privileged EXEC command provides some useful
information about the forwarding results if a packet entering an interface is sent through the system. Depending
upon the parameters entered about the packet, the output provides lookup table results and port maps used to
calculate forwarding destinations, bitmaps, and egress information.
Most of the information in the output from the command is useful mainly for technical support personnel,
who have access to detailed information about the device application-specific integrated circuits (ASICs).
However, packet forwarding information can also be helpful in troubleshooting.

Using the show debug command

The show debug command is entered in privileged EXEC mode. This command displays all debug options
available on the switch.
To view all conditional debug options run the command show debug condition The commands can be listed
by selecting either a condition identifier <1-1000> or all conditions.
To disable debugging, use the no debug all command.
Caution Because debugging output is assigned high priority in the CPU process, it can render the system unusable.
For this reason, use debug commands only to troubleshoot specific problems or during troubleshooting sessions
with Cisco technical support staff. Moreover, it is best to use debug commands during periods of lower
network traffic and fewer users. Debugging during these periods decreases the likelihood that increased debug
command processing overhead will affect system use.

Troubleshooting Packet Loss

If your system exhibits partial or full loss of network connectivity or packet loss, perform basic troubleshooting
procedures to eliminate the common causes. The common causes include:
System Management Configuration Guide, Cisco IOS XE Bengaluru 17.4.x (Catalyst 9400 Switches)
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