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Hierarchy Level

[edit chassis]


Set the chassis ambient temperature and instruct the power manager to allocate power to the line cards according to the ambient temperature value.

On system initialization in a PTX Series router, the power manager reads the ambient temperature and allocates power to the line cards according to the power budget policy at that temperature. If the actual power consumption of any line card exceeds the configured value for more than three minutes, the power manager overrides the configured ambient temperature setting of that line card, and resets its ambient temperature to the next higher level and reallocates power according to the new temperature setting. All the overshooting line cards remain in the dynamic ambient temperature mode until the next reboot, or until you override the configured ambient temperature with a CLI command. The power manager then resets the power budget of the FRUs according to the configured ambient temperature setting.

When an MX Series router or an EX9200 switch restarts, the system adjusts the power allocation or the provisioned power for the line cards on the basis of the configured ambient temperature. If enough power is not available, a minor chassis alarm is raised. However, the chassis continues to run with the configured ambient temperature. You can configure a new higher ambient temperature only after you make more power available by adding new power supply modules or by taking a few line cards offline. By using the provisioned power that is saved by configuring a lower ambient temperature, you can bring more hardware components online.

For MX960 Universal Routing Platform and the MX2000 line of routers, a maximum operating temperature of 40°C is recommended at an altitude of up to 6000 feet above sea level. The router can operate up to a maximum temperature of 46°C at sea level and can be set accordingly.


If ambient temperature is not set, then the line cards are allocated power according to the default ambient temperature.


  • MX Series routers—40°C

  • PTX Series routers—40°C

  • EX9200 switches—40°C

  • EX9251 switches—40°C

  • EX9253 switches—40°C



Set the ambient temperature of the chassis to 25°C


Set the ambient temperature of the chassis to 40°C


Set the ambient temperature of the chassis to 55°C


Starting in Junos OS Evolved Release 19.1R1, the PTX10003-80C routers do not support configuration of the ambient temperature value 55C.

Required Privilege Level

chassis—To view this statement in the configuration.

chassis-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 14.1.