BACnet IoT Gateway Start-up Guide
Page 49 of 60
APPENDIX B
REFERENCES
Appendix B.1. Understanding FDR
The BACnet IoT Gateway
doesn’t allow FDR, local IP and BACnet MS/TP to co-exist because there is no
guarantee that two distinct BACnet networks will have unique Device Instances or Network Numbers.
(Unique Device Instances and Network Numbers are a requirement for BACnet to function properly). If local
and remote options were allowed concurrently, the BACnet IoT Gateway would connect two networks that
are probably not designed to work together. Forcing this situation would create extremely difficult to
diagnose problems.
Appendix B.2. Understanding BACnet BBMD and NAT Routing
The BACnet IoT Gateway does not support NAT routing. However, the BACnet IoT Gateway must have
the external IP Address and IP Port that the NAT router assigns to it, because these are inserted into the
BACnet/IP BVLC header as the source IP Address which a remote recipient can use to reach the BBMD
(BACnet Broadcast Management Device). This is necessary because the messages are distributed again
by a remote BBMD, and the remote recipient of a distributed broadcast needs to reach the originator of the
broadcast.
Figure 62: BBMD Scenario 1
– Interconnected IP Network
