Example: BACnet BBMD

For an introduction and documents about BACnet/IP and BBMD, see BACnet Community – Developer Aids.

To simulate a complex network environment, a LANCOM VPN router is used. There are two VLANs to separate the BACnet devices. BACnet broadcasts (also IP/UDP broadcasts) to devices outside of the VLAN are rejected by the LANCOM VPN router. As a result, the BACnet devices in one VLAN cannot communicate directly with the BACnet devices in the other VLAN, but need "their" BBMD to do so.

The LANCOM VPN router is configured to perform IP routing between the two VLANs. This makes sure that the BBMDs can communicate "peer-to-peer" (P2P) via IP.

In general, the BBMD configuration should be a "fully connected star". In this particular example, the BBMD configuration is simple: the two BBMDs only need to recognize each other.

Network view:

Application view:

To demonstrate that the BACnet devices can communicate properly, each device executes a "client read property" from another device and sets its AV1.PV to the read value.

Analog_Value[1].Present_Value (short form: AV1.PV)

BACDEV1 increases its AV1.PV after successful reading. In this way, you can see that all BACnet devices increase your AV1.PV when the "ring" is closed (or not interrupted).