Master Slave with LM5

[Kuru]

the DALI - is it KNX DALI gateway?
LM communicates with the Schneider Gateway via BACnet - what do you mean here? Is LM bacnet server or client?
Modbus - is it RTU or IP?
Two LMs can't have same IP so in any case this will need to be manually switched to new url.

DALI is controlled via a KNX DALI gateway.
The LM communicates with the Schneider gateway via BACnet, where the LM acts as the BACnet server.
Modbus communication is over RTU.
The two LMs will be assigned different IP addresses.
In the event of a master LM failure, the slave LM must automatically take over control.