Description

This article explains the meaning of 'FPC x Airflow mismatch in the system ' alarm and the steps to overcome it.

Symptoms

Active Alarm on the device:

user@host> show chassis alarms no-forwarding
2020-03-15 14:30:38 CEST Major  FPC 1 Airflow mismatch in the system

Error Logs:

Mar 15 14:30:38  craftd[1975]:  Major alarm set, FPC 1 Airflow mismatch in the system
Mar 15 14:30:48  craftd[1975]: Receive FX craftd clear alarm message: color: 1 class: 100 object: 143 slot: 1 id=318767503 reason=318767104
Mar 15 14:30:48  craftd[1975]: Major alarm cleared, FPC 1 Airflow mismatch in the system
Mar 15 14:30:52  jdhcpd: DH_SVC_SENDMSG_FAILURE: sendmsg() from 0.0.0.0 to port 67 at 255.255.255.255 via interface 5 and routing instance default failed: Network is down
Mar 15 14:30:53  alarmd[1974]: Alarm set: CB OPUS color=RED, class=CHASSIS, reason=FPC 1 Airflow mismatch in the system
Mar 15 14:30:53  craftd[1975]: Receive FX craftd set alarm message: color: 1 class: 100 object: 143 slot: 1 silent: 0 short_reason=FPC 1 Aflow mismatc long_reason=FPC 1 Airflow mismatch in the system id=3187

Solution

Verify the hardware status of Fans:

user@host> show chassis hardware
Hardware inventory:
Item             Version  Part number  Serial number     Description
<snip>
FPC 1            REV 18   6x1   Txxxxx         QFX5100-48S-6Q
<snip>
Power Supply 0 REV 04   7x2   xxxxxx0   JPSU-650W-AC-AFI
Power Supply 1 REV 04   7x2   xxxxxx3   JPSU-650W-AC-AFI
Fan Tray 0                    QFX5100 Fan Tray 0, Front to Back Airflow - AFO  <-- Should be AFI
Fan Tray 1                    QFX5100 Fan Tray 1, Back to Front Airflow - AFI
Fan Tray 2                    QFX5100 Fan Tray 2, Back to Front Airflow - AFI
Fan Tray 3                    QFX5100 Fan Tray 3, Back to Front Airflow - AFI
Fan Tray 4                    QFX5100 Fan Tray 4, Back to Front Airflow - AFI

Reseat the Fan Module:

Manually reseat the FPC Fan. Please ensure you are maintaining minimum Fans to be seated in the chassis to keep the chassis up and running. While you perform this step, please check if the error Fan tray model is actually as displayed in the hardware status. It could be possible that the unknowing mixing of AFO and AFI in the system also throws this error.

Verify the status of Management Interface:

Example:

user@host> show interfaces em0 terse
Interface       Admin Link Proto    Local           Remote
em0             down  down
em0.0           down  down inet     x.x.x.x/24

Note: Depending on the product type, the management interface could be em0, me0, fxp0

This issue may be seen when the management board is down, the management port is faulty or the management Ethernet link is down.
In case you have manually disabled the management interface, please enable the same for the alarm to clear. If this does not help, proceed below.

Restart the FPC:

user@host> request chassis fpc (offline | online | restart) slot slot-number
<all-members>
<local>
<member member-id>

In our case, 

user@host> request chassis fpc restart slot 1

If the above steps do not resolve the problem, please contact your JTAC Representative .

Note: This issue is resolved in the following Junos versions: 17.2R3, 17.3R2, 17.3R3, 17.4R2, 18.1R1 and higher

Modification History

2021-03-17: Minor administrative edits.