FAC4911 controllers may be connected to a building automation network in multiple ways: as daisy-chained devices, as part of a star (also called home run) network, or as part of a ring network.
To daisy-chain FAC4911 controllers, connect the controllers to the bus supervisor in a chain with the Ethernet cable connecting to the FAC4911 at the ETH1 or ETH2 port and connecting to the next device from the other port. Benefits of daisy-chained networks are that they require less physical wiring and new devices can be added easily to the network.
In a star network, each FAC4911 controller is connected by ETH1 or ETH2 directly back to a main switch. This configuration reduces the possibility of network failure but requires more wiring to install.
A ring network is a chain of controllers virtually closed by a software component in an Ethernet switch. Not all switches support the ring topology. The dual-port controller from Johnson Controls supports Media Redundancy Protocol (MRP). MRP allows a chain of Ethernet devices to overcome any single communication failure, with a recovery time faster in a BACnet system.
For more information about network topologies for the BACnet/SC or BACnet/IP Controllers, refer to the Metasys IP Networks for BACnet/IP Controllers Configuration Guide Technical Bulletin (LIT-12012458) .