Example Internetwork Diagrams

Figure C.5 shows an internetwork with 2 BACnet routers and 4 BACnet networks.

Figure C.5. Four physical networks, 2 routers

In the example above, routers A and B join together three different media and link-layer types: BACnet over Ethernet (network 2), BACnet MS/TP (networks 11 and 22), and BACnet ARCnet (network 8).

Note that each BACnet node has a unique Device ID number (shown inside node). Note also that router A could actually be a JACE that is licensed for MS/TP, as shown in Figure C.6.

Figure C.6. BACnet Ethernet to MS/TP router functions provided by station in JACE.

In this case, the JACE’s station provides BACnet routing between the two MS/TP networks and Ethernet network.

On an Ethernet LAN, there may be two separate BACnet networks sharing the same media—BACnet over Ethernet and BACnet/IP, as shown in Figure C.7.

Figure C.7. Same physical Ethernet LAN, router joins two BACnet networks.

Again, note that each BACnet node has a unique Device ID number (shown inside node). Note also that this router function could actually be provided by a Niagara station, as shown inFigure C.8.

Figure C.8. BACnet/IP to BACnet/Ethernet router function provided by NiagaraAX station

In this case, you must be especially careful that no other router exists between the BACnet Ethernet and BACnet/IP networks—if the Niagara station detects this illegal (loop) configuration, the routing functions performed by the station are stopped.

This condition is indicated on the property sheet of the BacnetComm, Network component, where its “Routing Enabled” property has been automatically set back to false (from true). In such a case, corresponding entries are generated in the stations's LogHistory, noting detected misconfiguration and disabled BACnet router functionality.