Last Status Change date in Realtime Interface Monitor shows a future date

Overview

The Last Change field uses two OIDs to attain it's value:

ifLastChange(1.3.6.1.2.1.2.2.1.9): This static value reflects the value for sysUptime when the interface's Operating Status changed. For example, if the interface's operating status changed 60 seconds after the device was rebooted, the ifLastChange value will be 600 (hundredths of seconds) until the operating status changes again.

SysUptime(1.3.6.1.2.1.1.3): This value represents the amount of time in hundredths of seconds that the system has been up.

In order to calculate the Last Change value for the interface, ifLastChange is deducted from SysUptime. This gives us the amount of hundredths of a second since the change. We then compare that to the current date and time and we end up with the specific date and time of the change.

The limitation of this calculation is that SysUptime rolls over at 4,294,967,296 hundredths of a second. When this occurs, deducting ifLastChange from SysUptime results in a negative number, which then ends up as a futuristic date.

Environment

NPM version 10.x and 11.x

Cause 

The limitation of calculation that SysUptime rolls over at 4,294,967,296 hundredths of a second. When this occurs, deducting ifLastChange from SysUptime results in a negative number, which then ends up as a futuristic date.

Resolution

Reboot the device, which will reset all counters to 0.