Collecting Data from Multi-Subnet BACnet Network

Onboard can collect data from a multi-subnet BACnet network, provided the network is properly configured with BACnet Broadcast Management Devices (BBMDs).

📘 What is a BBMD?

BACnet devices discover one another by sending broadcast messages across the network. However, these broadcasts do not travel across subnets, which means devices on one subnet cannot automatically see devices on another.

A BACnet Broadcast Management Device (BBMD) solves this. It forwards BACnet broadcast messages between subnets, allowing devices across a multi-subnet network to communicate as if they were on the same local network. BBMDs are typically configured on BACnet controllers or routers by your IT or BMS team.

🔧 How It Works

Onboard's Edge Node does not have native BBMD capabilities, meaning it cannot independently broadcast discovery requests across multiple subnets on its own. However, it does not need to.

As long as the Edge Node is installed on the same subnet as a BBMD, it will discover all devices that the BBMD can see. No additional configuration is required on Onboard's end.

In practice, this means:

• The Edge Node leverages the existing BBMD routing already in place on your network.
• Any device reachable by the BBMD on the Edge Node's subnet will be discoverable by Onboard.
• Devices on subnets not reachable by the BBMD will not be visible to the Edge Node.

✅ What to Confirm Before Installation

If your building has mulitple BACnet networks, confirm the following with your IT or BMS team before installing the Edge Node:

• The server or VM where the Edge Node will be installed is on the same subnet as the BBMD.
• The BBMD is properly configured with table with routes to other BACnet networks.