Downstream device alerts are not being suppressed in Spectrum WLC Manager

Products

• Spectrum
• Network Observability

Issue/Introduction

This document details Fault Isolation/alarm suppression specifically for Cisco WLC Manager devices in Spectrum.

When some switches are discovered as an SNMP device and its a parent/upstream device. These have a number of child/downstream devices. When the upstream device goes down, all downstream devices are not going to suppress mode. Instead they create a large number of alerts.

Checking if EnableSuppressedAlarms (0x12ddf) attribute was set to TRUE, but it is set to FALSE on all the devices and WLC Manager as per default. When an upstream device goes down, all down-stream devices raise an alarm that is cleared in the same second:

Severity	Created On	Cleared On	Event	Created By	Cleared By	Event Type
	28/11/2021 2:32:42 PM		Model Switch-2 of type AccessPoint has been contacted.	System		10301
	28/11/2021 7:16:05 PM		AP disassociated from Switch.   When an Airespace AP disassociates from a Airespace Switch, the AP disassociated notification will be sent with the dot3 MAC address of the Airespace AP. This will notify the management system to remove Airespace AP from this Airespace Switch.   bsnAPMacAddrTrapVariable = XX:XX:XX:XX:XX:XX bsnAPName = Switch-2	System		4B60007
Critical	28/11/2021 7:18:24 PM	28/11/2021 7:18:24 PM	Device TSwitch2 of type AccessPoint has stopped responding to polls and/or external requests.An alarm will be generated.	System	System	10D35

 

The alarms appear to be raised and cleared in the same second on all the downstream devices in the WLC Manager when the upstream device goes down.

Environment

DX NetOps Spectrum Release : 20.2.x or later

Resolution

This behaviour is working as per design. Alarm generation on down-stream devices depends on the contact loss status detection either prior or after the upstream device contact status has been detected.

The following 2 scenarios demonstrate how this works:

Scenario 1 : Upstream device is down but spectrum first detected  contact loss status of down stream device before upstream device contact status was determined . In this case, the alarm will be  generated on down stream device. This generated alarm on down stream device will be  cleared when upstream device  contact status lost is detected .

Scenario 2 : Upstream device is down and  spectrum  detected  its contact loss status  before down stream device contact status is determined. In this case, the alarm is NOT generated on down stream device and it will be suppressed.