Issue
A large number of “Duplicate Network Identifier” alarms are generated when a BACnet network is shared between Schneider Electric and Third-party systems. Device discovery does not show duplicate device instance IDs or overlapping network IDs, and the alarms appear to originate from a BACnet gateway.
Product Line
EcoStruxure Building Operation
Environment
- EcoStruxure Building Operation ES / AS
- Site with Schneider Electric and Third-party managed BACnet networks
Cause
Packet analysis shows multiple devices responding to “Who-Is-Router-To-Network” with “I-Am-Router-To-Network” messages. This indicates that multiple devices are advertising the same BACnet network numbers at the network layer (NPDU). As a result, multiple routing paths to the same network are exposed, which is not permitted by the BACnet standard and leads to routing ambiguity and duplicate network identifier alarms.
Resolution
Identify all devices that respond with “I-Am-Router-To-Network” on the shared BACnet internetwork and reduce routing to a single designated gateway or router per network path.
To identify devices broadcasting the duplicate network IDs
- Capture BACnet traffic (e.g. Wireshark) on the relevant network
- Apply display filter such as
bacnet.npdu.network_layer_message == 0x00 || bacnet.npdu.network_layer_message == 0x01
- Identify the trigger request
Who-Is-Router-To-Network - Inspect all corresponding responses
from multiple devicesI-Am-Router-To-Network - Compare the advertised network numbers (Network List) in each response
- If multiple devices advertise the same network number, this confirms duplicate network identifiers
Align BACnet network configuration between Schneider Electric and Third-party systems to ensure that network numbers are unique and not advertised by multiple routers.
