Custom vCenter Alarm for dvPort Link Down Triggers Only Once

Products

• VMware vCenter Server

Issue/Introduction

On VMware vCenter Server, a custom alarm configured to monitor Distributed Port (dvPort) link-down events triggers successfully for the first event, but fails to trigger for subsequent dvPort down events. The alarm status remains stuck in a "Yellow" (Warning) or "Red" (Critical) state, preventing further notifications (SNMP traps or emails) for additional port transitions.

Environment

• Product: VMware vCenter Server
• Component: vCenter Server Management, Distributed Switch (vDS)
• Configuration: Custom vCenter alarm defined on Distributed Switches with trigger conditions based on dvPort link was down events.

Cause

vCenter Server alarms are event-based. When a custom alarm is triggered, the alarm instance transitions from "Green" to "Yellow" or "Red" and generates a vim.event.AlarmStatusChangedEvent.

Because there is no transition event (e.g., a "Green" transition) defined to reset the alarm, the instance remains in the triggered state. Subsequent matching events do not generate new AlarmStatusChangedEvent entries because the alarm is already in the triggered state. The alarm engine requires the state to return to "Green" before it can trigger the action again for the same event type.

Resolution

To ensure the alarm triggers consistently for every event, you must configure a "Reset" rule in the alarm definition. This allows the alarm to return to a "Green" state automatically when the port is reconnected, enabling it to trigger again upon the next link-down event.

Prerequisites

• Administrative access to the vSphere Client.
• Permission to modify alarm definitions.

Steps to configure a Reset Rule

1. Log in to the vSphere Client
2. Navigate to Configure > Alarm Definitions
3. Select the custom alarm and click EDIT
4. Click NEXT and navigate to Reset Rule 1
5. Toggle Reset the alarm to green switch to enabled
6. Add a reset rule using the following trigger:
   Trigger: dvPort link was up.
7. Ensure the "Reset the alarm to" criteria is set to Normal so that when this event occurs, the alarm status returns to "Green." and click NEXT.
8. Click SAVE to save the changes.

Alternative Workaround

If you cannot modify the alarm definition, you must manually reset the alarm status to "Green" after each triggered event:

1. Navigate to the Monitor > Triggered Alarms view in the vSphere Client.
2. Select the triggered custom alarm instance.
3. Click RESET TO GREEN.