Slave ID-based Routing

Slave ID-based routing is available to all types of supported Modbus devices, i.e., Modbus RTU, Modbus ASCII, and Modbus TCP devices.

ID-based routing rules are edited on the Slave ID-based routing settings page (tab). With Slave ID-based routing, you define up to eight ranges of Modbus IDs and specify the destination for each range (with possible ID shifting if necessary).

With slave ID-based routing, the Gateway will receive incoming requests from Modbus Masters:

  • On all active serial ports (channels).

  • On any of the four TCP ports.

The destination Modbus Slave for each range of IDs can be:

  • One of the active serial ports (channels).

  • One of the four Modbus TCP Slaves on the IP network. A dedicated page (tab) — TCP Slave Settings — allows you to set the IP address and port for each of the four Modbus TCP Slaves.

For example, you may specify that...

  • Requests with IDs from 1 to 10 should be routed to the serial port 1;

  • Requests with IDs from 11 to 20 should be routed to the serial port 2;

  • Requests with IDs from 21 to 25 should be routed to the TCP Slave 1.

routing-by-slave-id

Note that ID-based routing has lower priority than the TCP port-based routing. Meaning, if both routing methods are engaged and produce conflicting routing results, then port-based routing takes precedence.