Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 39)

Communication
3.2 Communication services
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
3-11
Routing network nodes: MPI - DP
Gateways between subnets are routed in a SIMATIC station that is equipped with interfaces
to the respective subnets. The figure below shows CPU 1 (DP master) acting as router for
subnets 1 and 2.
Subnet 1 (e.g. MPI)
Subnet 2 (e.g. PROFIBUS DP)
PG
S7-300
CPU (DP master)
S7-300
CPU (DP slave)
The figure below shows the access to an Ethernet subnet. CPU 1 (315-2 DP, for example) is
the router for subnet 1 and 2; CPU 2 is the router for subnet 2 and 3.