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[Junos] Major alarm: 'Host x RTC Battery failure'



Article ID: KB36035 KB Last Updated: 14 Jul 2020Version: 1.0

This article explains the meaning of the alarm, 'Host x RTC Battery failure' and how to overcome it.


Active Alarm:

user@host> show chassis alarms
1 alarms currently active
Alarm time               Class  Description
2020-02-11 02:19:56 EST  Major  Host 1 RTC Battery failure
  1. A glitch in the upgrade process
  2. RE issue
  3. RTC Battery worn out

RTC battery is the CMOS battery that the RE uses for time; it refers to the battery of the hardware clock.The "RTC Battery failure" alarm indicates that the hardware clock battery is dead. The battery failure results in the Real-Time Clock (RTC) getting reset and the BIOS settings such as the boot order stored in the CMOS getting cleared. Also, the router cannot have to keep its clock and calendar when it is powered off.

QFX/ PTX device:

On QFX and PTX series devices running prior to Junos 17.4 versions, these messages could be a false alarm and may be safely ignored. In that case, one workaround would be to configure a filter to filter out this error message from logging into Syslog. Refer to KB9382 - How to prevent certain syslog messages from being written to the log file.

On devices running versions after 17.4, follow the same troubleshooting procedure as mentioned for MX devices below.

MX device:

Re-attempt Upgrade Process:

In case this error has popped up post upgrade/downgrade, re-perform the same upgrade downgrade process by jumping to the previous version and then changing to the new version. There have been previous cases where the issue resolved after re-attempting the upgrade process even after a successful previous upgrade. Doing so, the alarm is likely to disappear due to its transient nature.

Try to stay on the latest recommended release when considering upgrades as suggested in KB21476 - Junos Software Versions - Suggested Releases to Consider and Evaluate.

Battery Change:

The issue could lie with the battery as well. It is better to change the battery and check if the issue resolves. The battery should lie on top right side of the routing engine (sometimes could be built-in). Note that this battery is not hot-swappable, so you should perform the replacement under a maintenance window. Once the battery is replaced, the alarm will ideally disappear. Even if the alarm persists after changing the battery with a new one, you can ignore the alarm until the next Junos upgrade (since you know that the battery is new) when the alarm will clear.

Hardware Replacement:

In cases where an upgrade cannot be performed and replacing the battery is not favorable to your situation, you can change the RE with a new one. Please contact JTAC for an RMA of the RE. In certain cases, where RE is built-in in nature, the entire chassis/CB will have to be replaced.

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