Configuring Fault-Tolerant S7 Connections on S7-400H / CPU 410-5H Using Onboard PROFINET Ports Without CP 443-1

In SIMATIC PCS 7 V8.1, configuring fault-tolerant S7 connections (S7-REDCONNECT) between redundant AS controllers (S7-400H or CPU 410-5H) and WinCC OS Servers equipped with CP 1623 communications processors is fully supported using the controller's onboard PROFINET/Industrial Ethernet interfaces without requiring external CP 443-1 communications processors. In NetPro, configure the onboard PN-IO interfaces on Rack 0 and Rack 1 onto a shared or redundant Industrial Ethernet subnet, and establish a fault-tolerant S7 connection from the WinCC OS Application. The HARDNET-IE S7-REDCONNECT V12 protocol stack automatically manages four-way redundant communications paths.

Architectural Evolution - Onboard PROFINET vs External CP 443-1

In classic SIMATIC PCS 7 systems running older S7-400H controllers (such as CPU 414-4H or 417-4H), achieving fault-tolerant Plant Bus communication to redundant WinCC OS Servers required inserting dedicated Industrial Ethernet communications processors (CP 443-1) into each sub-rack. The classic CPUs lacked integrated Ethernet ports capable of supporting S7-REDCONNECT.

With the introduction of modern S7-400H Firmware V6.0 and the flagship CPU 410-5H Process Automation controller in PCS 7 V8.0 and V8.1:
* The CPU features two integrated high-speed Industrial Ethernet / PROFINET interfaces onboard (PN-IO X5 and PN-IO X8).
* These integrated interfaces feature advanced hardware-accelerated protocol engines capable of handling both real-time PROFINET IO field communications and fault-tolerant S7-REDCONNECT transport channels.
* Installing external CP 443-1 communications cards is no longer required, reducing rack space, power consumption, and hardware procurement costs.

Hardware and Network Prerequisites for CP-Free Redundancy

To implement fault-tolerant S7 connections directly through the CPU onboard interfaces, ensure the following hardware and licensing prerequisites are met:
1. Controller Hardware: Redundant S7-400H pair (e.g., dual CPU 410-5H 6ES7410-5HX08-0AB0 or dual CPU 414-5H / 417-5H) connected via fiber-optic sync modules.
2. OS Communications Hardware: WinCC OS Servers equipped with CP 1623 (6GK1162-3AA00) or CP 1613 PCIe cards.
3. Software Licensing: SIMATIC NET HARDNET-IE S7-REDCONNECT V12 (or version-matching license) installed on each OS Server in Automation License Manager.
4. Network Topology: SCALANCE X-200, X-300, or XC-200 managed switches configured in a redundant ring (MRP) or dual-bus topology connecting CPU Rack 0, CPU Rack 1, OS Server 1, and OS Server 2.

Comparison Table - Onboard PN Interface vs CP 443-1 in Redundant PCS 7

The following table compares system attributes when utilizing onboard CPU PROFINET interfaces versus external CP 443-1 communications processors.

Architecture CharacteristicOnboard PN Interfaces (CPU 410-5H)External CP 443-1 ConfigurationHardware RequiredNone (Built into CPU)2x CP 443-1 modules (1 per sub-rack)Rack Slot Consumption0 slots2 physical rack slotsS7-REDCONNECT SupportFully Supported (ISO-on-TCP & ISO)Fully Supported (ISO & ISO-on-TCP)Maximum Data Throughput100/1000 Mbps Gigabit onboard10/100 Mbps (Standard CP 443-1)PROFINET IO Field Device SupportConcurrent PROFINET IO and Plant BusFieldbus only or Plant Bus onlySystem Procurement CostSignificantly LowerHigher (Additional module costs)Reference Siemens ManualPCS 7 Compendium Part A (Ch. 2.4.3)Classic PCS 7 Fault-Tolerant Systems

Step-by-Step Engineering and NetPro Configuration Workflow

Follow this verified procedure to configure fault-tolerant S7 communication directly through the onboard CPU interfaces:

Configure Hardware in STEP 7 HW Config:
* Open the S7-400H / CPU 410-5H station in HW Config.
* Double-click the onboard PROFINET interface (e.g., X5 / PN-IO) on Rack 0.
* Assign a static IP address (e.g., 192.168.1.10) and subnet mask (255.255.255.0).
* Attach the interface to your Industrial Ethernet subnet (e.g., Plant_Bus).
* Repeat the exact procedure for the onboard PROFINET interface on Rack 1, assigning a distinct static IP address (e.g., 192.168.1.11) on the same Plant_Bus subnet.
* Save and compile HW Config.
Configure WinCC PC Station Hardware:
* In HW Config for the OS Server PC Stations, verify that the CP 1623 is inserted in the virtual rack (Slot 3) and connected to the Plant_Bus subnet.
* Save and compile.
Configure Fault-Tolerant S7 Connection in NetPro:
* Open NetPro.
* Select the WinCC Application inside the OS Server PC Station.
* In the connection table, insert a new connection:
- Partner: Select the S7-400H / CPU 410-5H station.
- Type: S7 connection (fault-tolerant).
- Click OK.
- In the Connection Properties dialog:
- Confirm that NetPro automatically creates four redundant communication paths (Path 1: CP 1623 to CPU Rack 0; Path 2: CP 1623 to CPU Rack 1; plus secondary redundant CP paths if redundant CPs exist in the PC).
- Verify that the active interface uses the onboard PN-IO ports.
- Repeat for the redundant partner OS Server.
- Execute Network -> Save and Compile -> Check and compile everything.
Synchronize and Download PC Stations:
* Open Station Configuration Editor on both OS Servers.
* Set PG/PC Interface to PC internal.local.1.
* Download the PC Station configuration from SIMATIC Manager (PLC -> Download).
Compile and Download AS:
* Download the hardware configuration and connections to the CPU 410-5H.
* Perform an OS compile with Named Connections selected.

Verification

Confirm that the fault-tolerant connection operates with bumpless failover:

Verify NetPro Online Connection Status:
* In NetPro, select the WinCC Application and choose PLC -> Activate / Verify Connections.
* Confirm that the fault-tolerant S7 connection shows status Established.
Verify Live Process Data in WinCC Runtime:
* Activate WinCC Runtime on the OS Server.
* Confirm that process graphics update dynamically and all block icons show live values without connection disruption.
Execute Physical Cable Disconnect Test:
* Disconnect the Ethernet cable from the onboard port of CPU Rack 0.
* Confirm that WinCC Runtime experiences zero data interruption. The S7-REDCONNECT driver automatically routes packets through the onboard port of CPU Rack 1 in sub-milliseconds without triggering unhandled alarm bursts.

Limitations and Operational Precautions

IP Subnet Consistency: Both onboard CPU ports and the OS Server CP 1623 cards must reside within the same logical IP subnet unless high-performance industrial IP routers are deployed.
Avoid Combining Plant Bus and Fieldbus on a Single Port: While the CPU 410-5H supports concurrent PROFINET IO and Plant Bus on port X5, best practice in medium-to-large plants is dedicating X5 to the Plant Bus and X8 to decentralized PROFINET IO field devices (ET 200SP/HA) to prevent network congestion.
Firmware Prerequisites: Ensure CPU 410-5H firmware is at least V8.0 or V8.1 to support full S7-REDCONNECT features.

Engineer FAQ

Does S7-REDCONNECT on onboard ports require ISO protocol (MAC addressing)?

No. Unlike legacy S7-400H systems which communicated exclusively over Layer 2 ISO MAC frames, the CPU 410-5H onboard PROFINET interfaces support fault-tolerant S7-REDCONNECT over standard TCP/IP (ISO-on-TCP RFC 1006) as well as ISO.

Can standard commercial Intel NICs (SOFTNET) use onboard ports for redundancy?

Yes. If the OS Server uses standard Intel NICs with SOFTNET-IE S7-REDCONNECT, it can communicate redundantly with the CPU 410-5H onboard ports over ISO-on-TCP.

What is the maximum number of fault-tolerant connections supported by CPU 410-5H?

The CPU 410-5H supports up to 120 concurrent fault-tolerant S7 connections across its onboard communications channels.

Where is this architecture documented in Siemens manuals?

This architecture is officially detailed in the 'SIMATIC PCS 7 Compendium Part A - Configuration Guidelines', Section 2.4.3 (SIOS Entry ID 109756485).