In all NiagaraAX releases of the BACnet driver, support is provided for more than one link layer type, using multiple “network ports” under the Bacnet network’s BacnetComm, Network child container. BACnet/IP is the typical and default network port (IpPort) included in a new Bacnet network, with other port types available (EthernetPort, MstpPort) in the bacnet palette. The MstpPort, for support of a BACnet MS/TP device trunk, requires a station hosted by a QNX-based JACE.

Each port added must reference a different BACnet network number across a job’s “internetwork”. The range for BACnet network numbers is 1—65535. Enter this number in each port component’s property sheet, in the “Network Number” field (by default, this value is “-1”, which means undefined/inactive).

If installing a Niagara station on an existing BACnet internetwork, where one or more BACnet routers already exist, you need to know the assigned network number(s), and enter (as appropriate) in the network port(s) under the BacnetComm, Network container. Find the existing network number information in the configuration setup of the BACnet routers.

Note a station’s Bacnet network is not limited to only BACnet networks defined in its own network ports—as it automatically “learns” other remote networks, from global BACnet “I-Am” messages received from other devices (and routers) on remote networks. The station maintains a table of known BACnet networks under the network’s BacnetComm, Network child, in a “Router Table” component.

By default, the station automatically performs BACnet router functions across different BACnet networks. Often this is the desired configuration, especially when there are MS/TP trunks that attach to RS-485 ports on a JACE controller. However, multiple BACnet routes to the same network segment results in message flood issues, and is considered a misconfiguration. If this is detected, the station automatically disables BACnet routing by setting the “Routing Enabled” property (found in the Bacnet network’s BacnetComm, Network slot) to false. For related details, see the next section Internetwork = BACnet Routers.