Basic Documentation
BACnet networks with MS/TP trunks
Application examples
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Network designation VLAN ID Subnet Address range Default gateway
BA_Hvac 6 255.255.255.0 192.168.16.1 -- 254 192.168.16.254
BA_CC_BuB 7 255.255.255.0 192.168.17.1 -- 254 192.168.17.254
BA_Rfm 10 255.255.255.0 192.168.20.1 -- 254 192.168.20.254
DMS_FS20 11 255.255.255.0 192.168.21.1 -- 254 192.168.21.254
An IP segment can also be divided on a project-by-project bases into a part with static addresses, e.g.
automation stations, etc., and a dynamic part (DHCP), e.g. for engineering laptops.
As an alternative, you can also work in general with DHCP. You must ensure, however, that the stations
always have the same IP address. This applies to:
● BACnet device that assume BBMD functionality.
● Room automation stations with an on-board web server and are operated with ABT SSA for servicing
and diagnostics.
Planning and implementation, BACnet network
Each Desigo PXC.. automation station should have FDT functionality for maintenance and diagnostics and
remote access.
A BACnet internetwork is built using a multiple BACnet networks. The IP segment as well as each MS/TP
segment forms a BACnet network. A BBMD must be used in each IP segment in order for BACnet and IP
networks to interact. This permits isolating local broadcasts from the flexible room management
(room/room segment). Global broadcasts, originating from central functions, are managed on the BACnet
device that assumes the BBMD functionality by asymmetrical BDT entries (Broadcast Distribution Table).
Set up the device accordingly in the XWP network configurator. The following table provide an overview of
the BACnet configuration:
Device name BNR501 ISP01AS01 F1BNR01 F2BNR01 F3BNR01 F4BNR01
Device Type PXG3.M PXC100-E.D PXG3.M PXG3.M PXG3.M PXG3.M
IP address 192.168.15.250 192.168.16.1 192.168.11.10 192.168.12.20 192.168.13.30 192.168.14.40
BACnet Network
no.
NET100 NET100 NET01 NET02 NET03 NET04
UDP port BAC0 BAC0 BAC0 BAC0 BAC0 BAC0
IP segment 05 06 01 02 03 04
BBMD true true true true true true
BDT
IP address 192.168.15.250 192.168.16.1 192.168.11.250 192.168.12.250 192.168.13.250 192.168.14.250
192.168.11.10 192.168.15.250 192.168.15.250 192.168.15.250 192.168.15.250 192.168.15.250
192.168.12.20 - - - - -
192.168.13.30 - - - - -
192.168.14.40
192.168.16.1 - - - - -
Function Central BBMD
(is the node for
all broadcast
messages
between VLAN
01-07
Main HVAC plant
BBMD
BBMD for
VLAN01
BACnet MS/TP
IP router to the
DXR on the 1st
floor
BBMD for
VLAN02
BACnet MS/TP
IP router to the
DXR on the 2nd
floor
BBMD for
VLAN03
BACnet MS/TP
IP router to the
DXR on the 2rd
floor
BBMD for
VLAN04
BACnet MS/TP
IP router to the
DXR on the 4th
floor
How and why asymmetrical BDT entries?
Local broadcasts that use the flexible room management to locate and address room segments from the
room, are routed to an own VLAN or BACnet network to a defined UDP port (0xBAC0). Local broadcasts are
thus encapsulated and no longer forwarded to other networks.