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The IOS and Its User Interface 33
NOTE
The no debug all command disables all debugs. Before enabling an unfamiliar debug
command option, issue a no debug all and then issue the debug you want to use; then, quickly
retrieve the no debug all command. If the messages are voluminous, press Enter immediately
to try to prevent the router from crashing by immediately disabling all debugs.
Users might or might not be interested in seeing the messages as they occur. The console port
always receives syslog messages. When a user telnets to the router, however, no syslog
messages are seen unless the user issues the terminal monitor command. This command
simply means that this terminal is monitoring syslog messages. Another alternative for viewing
syslog messages is to have the IOS record the syslog messages in a buffer in RAM, and then
use the show logging command to display the messages. For Telnet users, having the messages
buffered using the global config command logging buffered is particularly useful. Because
Telnet users do not get syslog messages by default anyway, these users can wait and look
at syslog messages when desired. Finally, the logging synchronous line configuration
subcommand can be used for the console and vtys to tell the router to wait until the user's last
command output is displayed before showing any syslog messages onscreen. That provides a
little less interruption for the user.
Syslog messages also can be sent to another device. Two alternatives exist: sending the
messages to a syslogD server, and sending the messages as SNMP traps to a management
station. The logging host command, where host is the IP address or host name of the syslog
server, is used to enable sending messages to the external server. After SNMP is configured, the
snmp-server enable trap tells the IOS to forward traps, including syslog messages.
Figure 2-5 summarizes the flow of syslog messages, including debug messages. For a more
detailed view of syslog messages, including restricting messages based on message severity,
refer to the IOS documentation CD manual called "Troubleshooting Commands."
ch02.fm Page 33 Monday, March 20, 2000 4:57 PM