Merge Industrial Ethernet Subnets for a PCS 7 Redundant Plant Bus
For a PCS 7 redundant plant bus, merge the corresponding subnet definitions across multiproject subprojects, but keep the two redundant paths as separate networks. Configure and merge the A-side subnets together and the B-side subnets together, with the separate IP ranges required by the documented architecture. Then assign the actual CP/interface connections and verify failover; the merge operation alone does not configure or prove redundancy.
Table of Contents
- Merge matching networks, not the redundant paths together
- Prepare the network objects
- Merge the subnets in the multiproject
- Assign interfaces and addresses
- Verification
- Limitations and Operational Precautions
- Engineer FAQ
- Technical References
- Related Articles
- Related Tags
Merge matching networks, not the redundant paths together
In a PCS 7 multiproject, subnet objects belonging to separate subprojects can be merged so stations share a cross-project network. For a two-bus redundant design, keep Plant Bus A and Plant Bus B as distinct networks with separate address ranges. Merge corresponding A subnet definitions across project subprojects into one A network, and corresponding B definitions into one B network; do not combine A and B into the same subnet.
Prepare the network objects
Before merging, identify each project's AS and OS subnets, which interfaces belong to each bus, the intended IP range, and the release-specific H-system/CP topology. Siemens' PCS 7 fault-tolerant systems manual specifies separate IP ranges for Bus1 and Bus2 in its redundant plant-bus architecture. The source question provides no screenshot, so verify the planned design against its actual hardware.
Merge the subnets in the multiproject
Siemens multiproject guidance describes the merge operation in SIMATIC Manager or NetPro. In the installed release, open the multiproject subnet merge/unmerge function, select the matching project subnets for one logical bus, and add them to the global network using the interface controls. Repeat separately for the other redundant bus. The documented menu path in the cited guide is File > Multiproject > Adjust Projects... or, from NetPro, Edit > Merge / Unmerge Subnets...; labels may vary by release.
Assign interfaces and addresses
Verify that each CP 443-1/interface is connected to the intended bus object and that Bus A and Bus B addresses use their separate ranges. Do not rely on network names alone; inspect the physical cabling, subnet IDs, IP addresses, and NetPro connection endpoints. Use the exact CP, CPU, and PC station topology supported by the installed PCS 7 release.
Verification
Check the resulting multiproject network view to ensure all intended A-side interfaces share Bus A and all B-side interfaces share Bus B, with no accidental cross-merge. Inspect the redundant connection paths, then test each bus and supported failover during planned commissioning. Siemens warns to check component redundancy behavior during commissioning.
Limitations and Operational Precautions
The source question's architecture image is unavailable here, and its exact CPU/rack/CP arrangement is not stated. The cited fault-tolerant manual is PCS 7 V8.1 SP1; the multiproject merge guide is V9.0. Match the installed release and hardware. Changing a live plant-bus topology can interrupt AS/OS communication; back up the multiproject and use approved change control.
Engineer FAQ
Should the two redundant bus subnets be merged with each other? No. Keep the redundant paths as separate networks; merge corresponding definitions across project subprojects for each path.
Why merge subnets at all? To create a shared cross-project network representation so stations in separate subprojects can communicate.
Can both buses use one IP range? The cited PCS 7 V8.1 SP1 manual specifies different IP ranges for Bus1 and Bus2.
Does merging prove redundancy works? No. Verify hardware paths and planned failover separately.
Technical References
- Siemens, Fault-tolerant Process Control Systems (V8.1 SP1), section 4.3, “Configuration – redundant, fault-tolerant plant bus,” describes Bus1/Bus2, separate IP ranges, and commissioning checks: https://cache.industry.siemens.com/dl/files/535/90682535/att_842352/v1/ps7red_b_en-US.pdf
- Siemens, PCS 7 multiproject engineering guide, Entry ID 22258951, “Generating cross-project networks,” describes merging project subnets in NetPro: https://support.industry.siemens.com/cs/attachments/22258951/22258951_DOCU_MP_MU_PCS7_V100_en.pdf