User Manual

BACnet networks with MS/TP trunks
Application examples
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Benefits
● The backbone is executed redundantly as ring.
● The smaller, e.g. unmanaged switches are connected in a star topology based on importance or price
pressure.
● Cost savings during installation.
● Compromises are possible, e.g. more important devices can be planned directly on the ring switch.
Disadvantages
● Distribution switches typically support SNMP; a failure can be reported via the Desigo CC management
platform. This would go unnoticed in this topology.
● The probability of failure increases for switches connected in a star topology.
For details, see Section 3.3.5 in Practical guide on IP networks in building automation and control
(CM110668).
Summary
The following tables show how to depict all devices and network components in a midsized to large project.
Plant category Number of IP devices Number of MS/TP devices
PXC primary plants 3
DXR2 individual room control 400
PXC00-E.D system controller, floor scope 4
PXC00-E.D system controller, building scope 1
DXR2.E18 for central functions, floor scope 4
DXR2.E18 for central functions, building scope 2
PXG3.M as BBMD, routing to by BACnet MS/TP 8
PXG3.M, as central BBMD, building scope 1
Reserves 5% 1 20
Amount 24 420
Network components Type Siemens Layer Managed No.
Edge switch on the floors XB-005 2 No 4
Distribution switch per floor XB-200 2 Yes 6
Core switch in the equipment rooms XM 400 3 Yes 1