A BBMD, or BACnet broadcast management device, sends a unicast message from one BACnet or IP device on a subnet to other subnets. Once the message gets to the destined subnet, the message is rebroadcast. A duplicate BBMD is where multiple devices on the same network are set as BBMDs, and are rebroadcasting the same messages. Let’s look at how to solve duplicate BBMDs with visual BACnet fast in this video tutorial.
A BBMD, or BACnet broadcast management device, helps different parts of a building’s network talk to each other. It takes a message from one BACnet or IP device and passes it to other sections of the network. When the message reaches the right part of the network, it gets broadcast again so all devices there can receive it.
Problems happen when there’s more than one BBMD on the same network. These “duplicate BBMDs” all try to send out the same messages at the same time, which clogs up the network. This extra traffic can overload devices and slow everything down—or even crash the network completely.
Visual BACnet can spot this problem with its “Duplicate BBMD” check. It looks for cases where the same device is getting the same message from more than one place.
Duplicate BBMDs usually show up because of setup mistakes, especially on sites with equipment from different vendors. For example, the first vendor may install BBMDs to connect multiple networks. Later, another vendor comes in to add more devices and installs their own BBMDs—without removing the original ones. Over time, you end up with two, three, or even more BBMDs per network, which leads to a big spike in network traffic. Ideally, there should only be one BBMD on each network.
To fix the issue:
- Use Visual BACnet to identify which vendors and devices are involved by checking IP addresses, vendor IDs, and MAC addresses.
- If devices don’t need to work across different networks, keep those networks separate.
- If they do, choose one vendor to manage the BBMDs.
As a best practice, it’s easier to manage changes if only one vendor handles all BBMDs across the site. Want to dive deeper? Watch our full webinar for more insights!
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