Connecting IP Devices to an IP Network
ECLYPSE User Guide 35
Spanning Tree Protocol
Switches and routers that support Spanning Tree Protocol (are IEEE 802.1D certified) are
able to detect and eliminate a loop from being formed on the network by disabling any port
on the router that is causing a loop. Such switches can be used to enhance network
availability by allowing you to create a ring network of controllers that is resistant to a single
point network failure (a cut wire for example).
In this scenario, non-PoE controllers are connected in a loop (or ring) such that the last
controller is connected back to the switch / router. Under normal operation, the switch /
router disables one of the ports to prevent a packet storm. This is shown below.
The Router / Switch’s Spanning Tree
Protocol has Blocked this Port
To Other IP Devices
Wired Router / Switch
Daisy-Chained BACnet/IP
Controllers
X
Figure 5-4: Wired Network Connection: Spanning Tree Protocol – Normal
Operation
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