Cisco 3850 tempreture details

[Noovi]

Hi Guys,

i have one Cisco 3850 switch and below is output of temp command.

KABZ1061#sh environment temperature status
Inlet Temperature Value: 29 Degree Celsius
Temperature State: GREEN
Yellow Threshold : 46 Degree Celsius
Red Threshold : 56 Degree Celsius

Hotspot Temperature Value: 44 Degree Celsius
Temperature State: GREEN
Yellow Threshold : 105 Degree Celsius
Red Threshold : 125 Degree Celsius

can you please let me know difference between Inlet Temperature and Hotspot Temperature value?

[andresfr · Accepted solution]

Hello Vineet!

I hope you're doing great.

Regarding this subject:

* Inlet temperature refers to the temperature of the ambient, the temperature at the air inlets inside the chassis.

* HotSpot temperature refers to the sensor placed within the switch where the temperature is typically the hottest in the chassis, usually near the CPU. That's why you see a major value for this temperature and the corresponding thresholds.

Status Green indicates the temperature is normal or the device is not heating up and has good airflow.
Yellow represents a warning the temperature is going high than normal.
Red is when there might not be sufficient airflow or the device is heating up because of other external or internal factors and need to check the environment around the switch.

There can be many factors which determine the temperature values like airflow to the device,  if the room has air-conditioned, and how far the other devices are placed.

I hope you find this information useful.

Regards,

[Noovi]

Thanks andresfr

[ljaimese]

The switch calculates the temperature using a function that contains the 3-point moving average temperature sensor type: temperature type (inlet, outlet, and hotspot)

latest_temp: latest temperature that is read

asic_num: This field is only applicable for hotspot temperature

The outlet temperature is not used to control any temp of the system it is displayed just for information purposes, and the same should not be used as an indication for any thermal issue.

Inlet and hotspot temperature should be used for any thermal monitoring.

-5C to +45C specifies the “long term” ambient air temperature at the inlet of the system.

-5C to +55C specifies the “short term” ambient air temperature at the inlet of the system.

+125C is the maximum allowed junction temperature for our ASIC UADP (hotspot).

The outlet temperature will depend on the inlet temp and load of the system (indirectly hotspot and that is why maybe the threshold was kept the same as a hotspot) so in case of any temperature alert should get caught with either inlet or hotspot.

if the temperature is going till 105C and the system reloads then we should have a hotspot temperature violation warning on this as well as logs in obfl.

The max junction temp of the ASIC is 125C. That is why it is the red threshold and IOS will react to the red threshold to protect the switch. The switch will run just fine once it hits 105C until it hits 125C.

The only way that the device will reach 105C is if there is a faulty fan. The fan fault will be indicated by IOS well before the hotspot temp thresholds will be reached.