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[MX] FPC temperature mismatch on MPC8 / MPC9 after upgrading to 17.2 version

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Article ID: KB36015 KB Last Updated: 16 Jul 2020Version: 1.0
Summary:

This article explains the temperature mismatch behavior exhibited by MX2k devices (MX2008, MX2010, MX2020) and also provides the steps to resolve it.

Symptoms:

The chassis FPC temperature increases up to 20 degrees Celsius after upgrading Junos version to 17.2.

Check the hardware inventory for FPC type:

user@R1> show chassis hardware
Hardware inventory:
    Item             Version  Part number  Serial number     Description
    Chassis                                <masked>           MX2020
    <snip>
    FPC 2            REV 26   750-063414   <masked>           MPC9E 3D
      <snip>

Before Upgrade:

user@host> show chassis fpc 2                 
                     Temp  CPU Utilization (%)   CPU Utilization (%)  Memory    Utilization (%)
Slot State            (C)  Total  Interrupt      1min   5min   15min  DRAM (MB) Heap     Buffer
  2  Online            39     19          0       17     16     11    3136       16         22

user@host> show chassis fpc 2 detail 
Slot 2 information:
  State                          Online    
  Temperature                      39  <-- Matches the temperature displayed in show chassis fpc 1
  Total CPU DRAM                 3136 MB
  Total XR2                      1028 MB
  Total DDR DRAM                 24576 MB
  <snip>
user@host> show chassis environment fpc 2 | match temp 
  Temperature Intake         39 degrees C / 86 degrees F                 
  Temperature Exhaust A      53 degrees C / 127 degrees F            
  Temperature Exhaust B      44 degrees C / 111 degrees F 

SNMP Poller output:

 user@R1> show snmp mib walk jnxOperatingTemp |match .7.    
    jnxOperatingTemp.7.1.0.0 = 34
    jnxOperatingTemp.7.3.0.0 = 39   <-- This is the Intake Temperature of FPC2 displayed here 
    jnxOperatingTemp.15.7.0.0 = 41
    jnxOperatingTemp.22.7.0.0 = 32
    jnxOperatingTemp.22.7.1.0 = 32
    jnxOperatingTemp.22.7.2.0 = 32
    jnxOperatingTemp.22.17.0.0 = 31
    jnxOperatingTemp.22.17.1.0 = 31
    jnxOperatingTemp.22.17.2.0 = 31

After Upgrade:

user@host> show chassis fpc 2                 
                     Temp  CPU Utilization (%)   CPU Utilization (%)  Memory    Utilization (%)
Slot State            (C)  Total  Interrupt      1min   5min   15min  DRAM (MB) Heap     Buffer
  2  Online            53     19          0       17     16     11    3136       16         22

user@host> show chassis fpc 2 detail 
Slot 2 information:
  State                          Online    
  Temperature                    30       <-- Does not match the temperature displayed in show chassis fpc 1
  Total CPU DRAM                 3136 MB
  Total XR2                      1028 MB
  Total DDR DRAM                 24576 MB
  <snip>
user@host> show chassis environment fpc 2 | match temp 
  Temperature Intake         30 degrees C / 86 degrees F                 
  Temperature Exhaust A      53 degrees C / 127 degrees F            
  Temperature Exhaust B      44 degrees C / 111 degrees F            
  Temperature EA0 TSen       53 degrees C / 127 degrees F            
  Temperature EA0 Chip       47 degrees C / 116 degrees F            
  Temperature EA0_XR0 TSen   53 degrees C / 127 degrees F            
  Temperature EA0_XR0 Chip   55 degrees C / 131 degrees F            
  Temperature EA0_XR1 TSen   53 degrees C / 127 degrees F            
  Temperature EA0_XR1 Chip   59 degrees C / 138 degrees F   
Cause:

‚ÄčThis is seen because show chassis FPC is displaying the Exhaust temperature for FPC and show chassis FPC detail displays the Intake temperature. For detailed temperature values, one can refer show chassis environment output.

Also, from the SNMP output, one can verify that the operating temperature for FPC 2 matches the exhaust temperature unlike as seen on the previous version before the upgrade (where the intake temperature is matched)

SNMP Poller output:

 user@R1> show snmp mib walk jnxOperatingTemp |match .7.    
    jnxOperatingTemp.7.1.0.0 = 34
    jnxOperatingTemp.7.3.0.0 = 53    <-- This is the Exhaust Temperature of FPC2 displayed here 
    jnxOperatingTemp.15.7.0.0 = 41
    jnxOperatingTemp.22.7.0.0 = 32
    jnxOperatingTemp.22.7.1.0 = 32
    jnxOperatingTemp.22.7.2.0 = 32
    jnxOperatingTemp.22.17.0.0 = 31
    jnxOperatingTemp.22.17.1.0 = 31
    jnxOperatingTemp.22.17.2.0 = 31

This is the reason the difference in temperature is seen since the OIDs match different temperature values before and after the upgrade.

Solution:
This is a known issue reported via PR1339077 - fpc temperature mismatch for mpc8/9 on mx2k platform and has been resolved in the following releases:
  • junos:17.3R3-S2
  • junos:17.4R2-S2
  • junos:17.4R3
  • junos:18.1R1
  • junos:18.1R2
  • junos:18.2X75-D5
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