'VM network has dropped transmit packets' alarm happens after upgrading to Aria Operations 8.18.6

Products

• VMware Aria Operations (formerly vRealize Operations) 8.x

Issue/Introduction

After upgrading to VMware Aria Operations (formerly vROps) 8.18.6, a significant increase is in the frequency of the following alarm is observed:

• VM network has dropped transmit packets

The alert was either non-existent or infrequent prior to the 8.18.6 update.

Environment

VMware Aria Operations 8.18.6

Cause

The alert definition for network packet drops was intentionally redesigned in version 8.18.6 to provide more granular monitoring. Specifically, the new definition now tracks percentage-based thresholds in addition to raw packet counts. Even if the total number of dropped packets is low, a small "burst" of drops relative to total traffic (exceeding 1% or 4%) will now trigger a Critical or Immediate alarm. 

Threshold Comparison

Metric	8.18.5 (Old)	8.18.6 (New)
Critical	> 10 Total Dropped	> 400 Total Dropped OR > 4% Drop Ratio
Immediate	> 20 Total Dropped	> 100 Total Dropped OR > 1% Drop Ratio

Resolution

This behavior is working as designed. The increased frequency is likely due to VMs hitting the new percentage-based thresholds during collection cycles.
To manage these alerts, follow these steps:

1. Validate Performance: Review the affected VM’s Network | Peak Transmitted Packet Dropped within collection cycle (%) metric to confirm if the drops are sustained or momentary bursts.
   
   
2.  Adjust Policy (Optional): If the 1% or 4% thresholds are too sensitive for your specific environment:
   
   • Go to Configure > Policies.
   • Edit the active policy and locate the Alert Definition: VM network has dropped transmit packets.
   • Override the thresholds to align with corresponding performance design.
3. Check Infrastructure: If the alerts are valid, investigate potential congestion on the underlying ESXi host or physical switch ports.