Monitoring and Troubleshooting

Monitoring and Troubleshooting






Ping and traceroute are popular troubleshooting tools on any device, and Junos is no exception. There are some advanced options available though (see the command summary below).

Unlike some other vendors, Juniper rely heavily on log files, rather than just writing to screen. Log files are stored in /var/logs. The messages file, in particular, is very useful.

Often there are so many entries in a log file that it’s hard to find what you need. If you want to see just the most recent entries, show the log, and pipe it through the ‘last’ command.

We can monitor log files with the ‘monitor’ command. This shows the newest log entries on the screen as they are added.

Use match with monitor to filter in real-time.


Traceoptions are like debugs on other vendor devices. They are configured per feature that we want to troubleshoot.

Traceoptions write enties to log files, rather than to the screen, but we can use ‘monitor’ to see the entries on the screen as well.

Redirect traceoptions to a syslog server using destination-override syslog host.

If you want to limit who can access a traceoptions file, use world-readable or no-world-readable.

When logging, add explicit-priority to include syslog levels.


If you need assistance, you will need to call JTAC. It will help if you export logs and other relevant information ahead of time.


Command Summary

Command Mode Description
ping IP rapid Operational A rapid ping (Cisco style)
ping IP bypass-routing Operational Bypass the routing table for a ping
ping IP routing-instance NAME Operational Ping using a routing instance
traceroute monitor IP Operational Continually monitor a path
request system storage cleanup Operational Free up space
show log messages Operational Show the messages log
show log FILENAME Operational Show any log file
show system boot-messages Operational Show system boot logs
monitor start Operational Begin monitoring a file in real-time to see changes as they happen
monitor list Operational See a list of files being monitored
monitor stop Operational Stop monitoring a file
set system syslog host Configuration Configure a syslog server
set system syslog … source-address Configuration Configure a syslog source IP
set system syslog console Configuration Send syslogs to the console
monitor interface Operational See interface stats in real-time
monitor interface traffic Operational Monitor all interfaces at once
monitor traffic interface Operational A tcpdump style packet capture (traffic to the RE)
set … traceoptions file FILENAME flag ITEM Configuration Configure traceoptions
show chassis alarms Operational See any current alarms
show chassis environment Operational Check temperature, fan status, etc
show chassis temperature-thresholds Operational Check temperature warning levels
show chassis hardware Operational See the hardware in your platform
show chassis fpc Operational Get line card details
show chassis cluster Operational Get cluster information 
show chassis routing-engine Operational Get RE details
show system core-dumps Operational Collect core-dump information
show system alarms Operational Show system alarms
show system boot-messages Operational Show messages logged during boot
show system license Operational Show licensing information
show system storage Operational Show disk usage
show system uptime Operational See when the system last booted
show system process extensive Operational Show a full list of processes
request system halt Operational Power down the system
request system power-off Operational Power down the system
request system software add Operational Update Junos
request system configuration rescue save Operational Update the rescue configuration
request system configuration rescue delete Operational Delete the rescue configuration
request chassis routing-engine master switch Operational Change over the active RE
request chassis fpc slot NUMBER restart Operational Restart a line card
rollback rescue Configuration Load the rescue configuration
request support information | save /var/log/FILENAME Operational Collect JTAC support information
file archive compress source /var/log/* destination /var/tmp/FILENAME Operational Achive support information and logs, ready to be uploaded to JTAC
show chassis craft-interface Operational Shows the status of the LCD display on MX routers
set system syslog user USERNAME Configuration Send syslog messages to a users terminal (can use regex, facility, and severity to filter)
help syslog Operational Get help on syslog messages


Additional References



Compressing Troubleshooting Logs from /var/logs to Send to Juniper Networks Technical Support


Displaying Log and Trace Files


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