This article explains the possible reasons behind an RE's sudden reboot with the last reboot reason listed as 0x2:watchdog.

When you observed routing engine sudden reboots due to watchdog.The possible reason could be:

• Too much traffic is directed to the Routing Engine, such as a broadcast storm on fxp0.

• Hard drive or compact flash access is suddenly lost.

• Interaction issue between hardware.

• Power failure.

• Routing Engine memory error.

The 0x2:watchdog reboot reason indicates that the Juniper device's watchdog timer detected a fault and rebooted the system to prevent further issues. This watchdog timer monitors the system's health and automatically resets or reboots the device if it detects a fault or extended inactivity.

In this instance, the watchdog timer identified that the device was either unresponsive or experiencing a hardware issue, prompting a reboot to avoid potential damage. This safety mechanism is in place to ensure the device's stability and prevent data loss or corruption.

To prevent this from recurring, it's crucial to investigate the root cause. You should examine the system logs, hardware components, and software configurations to pinpoint the issue and take corrective measures.