Siemens SIMATIC S7-1200 - Page 1186

Communication processor and Modbus TCP
13.5 Modbus communication
S7-1200 Programmable controller
1186 System Manual, V4.2, 09/2016, A5E02486680-AK
Three MB_SERVER IP address variations are possible for the two MB_SERVER
instructions:
●
IP address = 0.0.0.0
Each MB_SERVER will respond to all Modbus TCP clients using any IP address.
●
IP address = Same IP address in TCPpassive_1 and TCPpassive_2
Both MB_SERVER connections only respond to Modbus clients originating from this IP
address.
●
IP address = Different IP number in TCP_passive_1 and TCP_passive_2
Each MB_SERVER only responds to Modbus clients that originate from the IP address
stored in their TCP_IP_v4 data.
Network 1:
Connection #1, Instance DB = "MB_SERVER_DB", within "Modbus
connections.TCPpassive_1" (ID = 1 and LocalPort = 502)
Network 2:
Connection #2, Instance DB = "MB_SERVER_DB_1, within "Modbus
connections.TCPpassive_2" (ID = 2 and LocalPort = 503)