Siemens SIMATIC S7-400 Manual page 66

Communication
4.2 Communication services
Routing gateways: MPI - DP
Gateways between subnets are routed in a SIMATIC station that is equipped with interfaces
to the respective subnets. The following figure shows CPU 1 (DP master) acting as router for
subnets 1 and 2.
Figure 4-1
4-14
Routing
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0