Description

This article provides information on how to isolate the cause of the fan tray failure issue.

Symptoms

There is an Alarm "Fan Tray x I2C Access Error" reported as below:

> show chassis alarms no-forwarding

6 alarms currently active
Alarm time Class Description
2023-09-19 11:01:56 CEST Major Fan Tray 3 I2C Access Error
2023-09-19 11:01:52 CEST Major Fan Tray 2 I2C Access Error
2023-09-19 11:01:50 CEST Major Fan Tray 1 I2C Access Error
2023-09-19 11:01:46 CEST Major Fan Tray 0 I2C Access Error
2023-09-19 10:58:48 CEST Major PEM 0 I2C Failure
2023-09-19 10:57:13 CEST Major PEM 1 I2C Failure

> show chassis environment no-forwarding

Class Item Status Measurement
Fans Fan Tray 0 Fan 0 Failed
Fan Tray 1 Fan 0 Failed
Fan Tray 2 Fan 0 Failed
Fan Tray 3 Fan 0 Failed

Solution

According to PR1690678, if there is an I2C failure, the I2C controller will be trapped in an error condition. All I2C access will fail after that failure, the root cause is, that when there is an I2C failure for some reason, the state of the I2C controller will be trapped in disabled even if the original failure is gone later.

The following software releases have been updated to resolve this specific issue: 
Junos OS: 21.4R3-S5, 21.4R3-S6, 22.1R3-S4, 22.2R3-S2, 22.2R3-S3, 22.3R3-S1, 22.4R1, 23.1R1

Note: The issue can temporarily be resolved by a reboot.

Modification History

21-2-2024

Related Information

PR1690678: https://prsearch.juniper.net/problemreport/PR1690678