Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Troubleshooting the MX104

Troubleshooting Resources for MX104 Routers

Command-Line Interface

The Junos OS command-line interface (CLI) is the primary tool for controlling and troubleshooting router hardware, the Junos OS, routing protocols, and network connectivity. CLI commands display information from routing tables, information specific to routing protocols, and information about network connectivity derived from the ping and traceroute utilities.

You enter CLI commands on one or more external management devices connected to ports on the front panel.

For information about using the CLI to troubleshoot the Junos OS, see the appropriate Junos OS configuration guide.

Front Panel LEDs

The front panel on the router contains LEDs that allow you to troubleshoot the router.

LEDs on the front panel include the following:

  • System LED—One LED labeled SYS OK on the front panel indicates the status of the router.

  • Alarm LEDs—One yellow and one red LED on the front panel indicate major and minor alarms.

For more information about component and front panel LEDs, see MX104 LEDs Overview.

Alarm Devices and Messages

When a major or minor alarm occurs, it logs the cause of the alarm. If the alarm relay contact is connected to alarm devices, the router also trips the corresponding alarm relay contact.

To view a detailed description of the alarm cause, issue the show chassis alarms command:

Understanding Alarm Types and Severity Classes on MX104 Routers

Before monitoring alarms on the router, become familiar with the terms defined in Table 1.

Table 1: Alarm Terms




Signal alerting you to conditions that might prevent normal operation. On a router, the alarm signal is the red system LED lit on the front of the chassis.

alarm condition

Failure event that triggers an alarm.

alarm severity

Seriousness of the alarm. The level of severity can be either major (steady red) or minor (blinking red).

chassis alarm

Predefined alarm triggered by a physical condition on the router or one of the router components. Alarms may be triggered by events such as a power failure, excessive component temperature, or media failure. Chassis alarms are preset and cannot be modified.

system alarm

Predefined alarm triggered by a missing rescue configuration or failure to install a license for a licensed software feature. System alarms are preset and cannot be modified, although you can configure them to appear automatically in the J-Web interface display or CLI display.

interface alarm

Predefined alarm triggered by a problem with a specific network interface.

Alarm Severity Classes

Alarms on the MX104 routers have two severity classes:

  • Major (steady red)—Indicates a critical situation on the router that has resulted from one of the following conditions. A red alarm condition requires immediate action.

    • One or more hardware components have failed.

    • One or more hardware components have exceeded temperature thresholds.

    • An alarm condition configured on an interface has triggered a critical warning.

  • Minor (steady yellow)—Indicates a noncritical condition on the router that, if left unchecked, might cause an interruption in service or degradation in performance. A minor alarm condition requires monitoring or maintenance.

    A missing rescue configuration generates a minor system alarm.

Verifying Active Alarms on MX104 Routers


Use the monitoring functionality to view alarm information for the MX104 routers, including alarm type, alarm severity, and a brief description for each active alarm on the router.


  • Observe the system LED on the front panel of the router. If the router is functioning normally with no alarms, the system LED lights green steadily.

  • Issue the CLI show chassis alarms command to verify the status of the router. As shown in the sample output, the value Class indicates the severity of the alarm.

    When the router is functioning normally with no active alarms, the CLI displays the output as shown:


Table 2 lists the alarm output fields.

Table 2: Alarm Output Fields



Alarm time

Date and time when the failure was detected


Alarm severity—either major or minor


Brief synopsis of the alarm

Monitoring System Log Messages on MX104 Routers


Use the monitoring functionality to view system log messages for MX Series routers.


To view events in the CLI, enter the show log command. For more information, see Displaying a Log File from a Single-Chassis System.