# Subnet Routing for the Siemens PLC driver

**URL:** <https://forum.inductiveautomation.com/t/subnet-routing-for-the-siemens-plc-driver/3986>\
**Category:** Ignition\
**Created:** [February 12, 2012, 7:33pm UTC](https://forum.inductiveautomation.com/t/subnet-routing-for-the-siemens-plc-driver/3986 "2012-02-12T19:33:18Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![chi](https://avatars.discourse-cdn.com/v4/letter/c/0ea827/32.png) [@chi](https://forum.inductiveautomation.com/u/chi)\
**Post date:** [February 12, 2012, 7:33pm UTC](https://forum.inductiveautomation.com/t/subnet-routing-for-the-siemens-plc-driver/3986/1 "2012-02-12T19:33:18Z")

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It would be nice to add routing support in the siemens driver. The S7-300 and 400 CPU’s support routing of incoming connections to the internal fieldbus (MPI/Profibus). In complex installations, there is often a master CPU connected to the ethernet, the slave CPU’s are connected to the fieldbus.  
As far as i can tell, it is necessary to add the subnet-id and the address/rack/slot of the target CPU to the connection request.  
I know this might be a bit difficult, as Siemens did not publish details about the S7-protocol.

Regards