User Manual

BACnet/IP networks
Designing BACnet/IP networks
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Yet another level for increasing reliability and redundancy is to employ two core switches at different
locations.
Cabling of distribution switches and Desigo room automation stations
The distribution switches can be cabled in a ring, if RSTP capable, which offer high reliability. The
important Desigo room automation stations (important rooms, central functions) are connected directly to
the distribution switch. Less critical Desigo room automation stations are cabled to either remote edge
switches or over daisy chain technology.
Desigo PXC3.E.../DXR2 room automation stations support cabling based on daisy chain topology. The max.
number is 20 devices and in the event of a failed automation station, all other stations are no longer
reachable.
Desigo room automation stations can be cabled as ring topology if higher reliability is required.
This requires support for layer 2 switches RSTP (Rapid Spanning Tree Protocol) as well as SNMP
monitoring and that any loss of superposed systems is reported.
In the event of a fault, switching the communication paths can take between 10 and 30 seconds.
DXR2/PXG3 automation stations route the RSTP protocol for the switches. It does not actually process the
RSTP protocol.
For details, see Section 3.3.5 in
Practical guide on IP networks in building automation and control
(CM110668).
Fiber Optics
Twisted Pair
B
C
A –
–
–
Distribution Switch
Edge Switch
C
A
Core Switch
C
A
B