The maximum number of connections and communication jobs that an S7-300 or S7-400 supports depends on the CPU and CP used.
Each connection requires connection resources for the end point or for the transition point (e.g. CP) on the stations concerned. The number of connection resources is CPU/CP-specific. If all the connection resources of a communication partner are occupied, no new connection can be set up.
More information on the maximum number of connection resources is available in the Technical data of the S7-300 CPUs.
More information on the maximum number of connection resources is available in the Technical data of the S7-400 CPUs.
An overview of the services and quantity frameworks that the CPUs with integrated PN interface support is available in Entry ID: 18909487.
Information on which communication connections of the Industrial Ethernet CPs need connection resources of the CPU is available in Entry IDs: 42480411 and 42480718.
Information on the maximum permitted number of simultaneous connections via CP is available in the relevant CP manuals in the chapter entitled "Performance Data".
An overview of the services and quantity frameworks that the Industrial Ethernet CPs of S7-300 and S7-400 support is available in Entry IDs: 16767769 and 15368142.