SNMP Trap triggered when resetting an alarm to green in vCenter Server

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

When an alarm is reset in vCenter Server, an SNMP Trap may be triggered. The received SNMP Trap will look similar to the following:

.1.3.6.1.4.1.6876.4.3.304.0 type=4 value=STRING: "Warning"
.1.3.6.1.4.1.6876.4.3.305.0 type=4 value=STRING: "Normal"
.1.3.6.1.4.1.6876.4.3.306.0 type=4 value=STRING: "alarm.HAfailoverInProgress"
.1.3.6.1.4.1.6876.4.3.307.0 type=4 value=STRING: "OBJECT_NAME_IN_VCENTER"
...

or

SNMPv2-SMI::enterprises.6876.4.3.304.0 type=4 value=STRING: "Warning"
SNMPv2-SMI::enterprises.6876.4.3.305.0 type=4 value=STRING: "Normal"
SNMPv2-SMI::enterprises.6876.4.3.306.0 type=4 value=STRING: "alarm.HAfailoverInProgress"
SNMPv2-SMI::enterprises.6876.4.3.307.0 type=4 value=STRING: "OBJECT_NAME_IN_VCENTER"
...

Note: The alarm name is not limited to "HA failover in progress." Additionally, the trap output format may vary depending on the SNMP Trap receiver.

Environment

VMware vCenter Server

Cause

This issue occurs when "Send SNMP traps" is enabled within the alarm's reset rules. By default, "Send SNMP traps" is disabled in the alarm's reset rules. If "Send SNMP traps" is enabled, a trap will be sent when the alarm is reset to Green, as shown in the example above. The SNMP Trap OID .1.3.6.1.4.1.6876.4.3.305.0 represents vmwVpxdNewStatus. Therefore, the above SNMP trap sample indicates that the alarm status has transitioned to Green (Normal) from Yellow (Warning) in vCenter Server. 

Resolution

To prevent SNMP traps from being triggered when an alarm is reset, perform the following steps:

1. Log in to the vSphere Client.
2. Select the inventory object where the alarm is configured.
3. Navigate to the Configure tab > Alarm Definitions.
4. Select the desired alarm and click EDIT.
5. Under Reset Rule X, turn off the Send SNMP traps toggle.
6. Complete the Edit Alarm Definition wizard to save the changes.

Additional Information

If your SNMP trap receiver is unable to decode VMware-specific OIDs, download the VMware MIB files from SNMP MIB module file download and import them into the SNMP trap receiver. Once the SNMP trap receiver correctly interprets .1.3.6.1.4.1.6876.4.3.305.0 as vmwVpxdNewStatus, you can determine that the trap is a benign notification indicating that the alarm was reset to Green.