Excessive BACnet Discovery

Overview

The Excessive BACnet Discovery diagnostic identifies situations where specific BACnet objects are repeatedly queried (WHO-HAS), flagging potential programming errors or unreachable/deleted objects. This diagnostic helps OptigoVN users identify misconfigured or outdated object name references.

These repeated broadcast messages can degrade network performance. Identifying and resolving these cases significantly improves system efficiency and clarity.

How The Diagnostic Works

The diagnostic monitors and groups "Who-Has" and "I-Have" BACnet messages within PCAP files. It detects cases where specific object names are repeatedly queried by a device, flagging potential programming errors or unreachable/deleted objects.

The diagnostic warning is triggered when "Who-Has" message rates exceed a set threshold (0.5 packet-per-minute (PPM) / 120 packets per hour). 

How to Fix It

Results of the diagnostic provide identifiers for specific devices that may require further investigation and tuning. These include:

• Requesting device
• Object name.
• Total count of Who-Has in packets per minute (ppm).
• Responding device address (if found).

Troubleshooting Flow

An Excessive Object Discovery event typically indicates that the source device is referencing a non-existent object name, causing it to repeatedly search for that name. 

To resolve this:

1. Update the programming in the source device to use the correct object name or remove the code if it is no longer necessary.
2. Run OVN to verify it has been corrected